Archive for September 2014

All-New 2015 Colorado and Canyon Debut

The 2015 Chevrolet Colorado (Fig. 1) and GMC Canyon (Fig. 2) set new standards for midsize trucks. These all-new models provide real truck capability and versatility to customers who don’t require a full-size truck.


2015 Chevrolet Colorado Z71

Fig 1


Three body configurations are offered: An extended cab model with a six-foot bed, a crew cab with a five-foot bed and a crew cab with a six-foot bed. The Colorado is available in WT, LT and Z71 trims. The Canyon is offered in SL, SLE and SLT models. All models of both trucks are available in 2WD or 4WD.


2015 GMC Canyon SLT Crew Cab Long Bed Front Three Quarter in Bronze Alloy Metallic - in studio

Fig 2




The Colorado and Canyon feature a standard 2.5L L4 engine (RPO LCV) rated at 200 hp (149 kw) and 191 lb-ft (259 Nm) of torque (Fig. 3), and a 3.6L V6 engine (RPO LFX), rated at 305 hp (227 kW) and 269 lb-ft (365 Nm), is optional. (Fig. 4)


F03 cc 25L L4 engine

Fig 3


F04 cc 35L V6 engine

Fig 4


Each engine features dual-overhead camshafts, jet-spray piston cooling, direct injection and variable valve timing to make the most of power and efficiency.


The engines are matched to a 6-speed automatic transmission (RPO MYB). A 6-speed manual transmission (RPO N8D) is available on the Extended Cab 2WD models equipped with the 2.5L engine.


To increase efficiency, the trucks also feature active aero grille shutters, which enhance aerodynamics by closing at certain highway speeds.


Available only on the Canyon is the AutoTrac automatic four-wheel drive system, which employs an electronically controlled transfer case. In Auto mode (Fig. 5), the transfer case operates in 2WD and automatically applies traction to the front wheels (4WD) when the vehicle senses wheel slippage.


F05 4 WD Controls lo res

Fig 5


Global Architecture


The midsize trucks use GM’s Global A electrical architecture, which is common with other newer GM vehicles. This architecture requires the use of the Global Diagnostic System 2 (GDS 2) software and the Multiple Diagnostic Interface (MDI) module.


Do not swap control modules in an attempt to diagnose a vehicle condition on the trucks. When certain modules are programmed and configured during installation, the module learns a specific environment identifier that is unique to the vehicle. If an incorrect immobilizer identifier or a specific number of incorrect environment identifiers are sent or received, vehicle starting is disabled.


Electric Power Steering


The belt-driven electric power steering system on the trucks consists of an integrated electromechanical power steering unit — containing the power steering control module, its sensors, the power steering motor, a belt drive and a ball nut mechanism — and the steering gear (rack and pinion).




The braking system on the Colorado and Canyon includes anti-lock brakes, traction control, electronic stability control and a hydraulic brake system with diagonal brake circuit split. The Electronic Brake Control Module (EBCM) and the brake pressure modulator are serviced separately. The brake pressure modulator uses a four circuit configuration to control hydraulic pressure to each wheel independently. The Duralife™ brake rotors, a GM-exclusive technology, feature a hardened and strengthened surface to reduce corrosion.


TIP: The new brake fluid has enhanced corrosion inhibitors and significant improvements in lubricity, engineered to eliminate master cylinder squeak/noise. Only use brake fluid GM P/N 19299818 (U.S.) or GM P/N 19299819 (Canada).


Additional braking system features include

• Dynamic Rear Proportioning –Reduces the rear wheel brake pressure by commanding the appropriate solenoid valves on and off under certain conditions.

• Auto Dry Brakes – Automatically activates in certain conditions by slightly applying the brakes to wipe away water from the brake rotors.

• Hydraulic Brake Assist – Actively increases the hydraulic brake pressure when the EBCM senses an emergency braking situation.

• Optimized Hydraulic Braking System – Supplements the brake system to maintain consistent brake performance under low brake booster vacuum conditions.

• Intelligent Brake Assist – Actively increases the hydraulic brake pressure when the EBCM senses a possible collision to help prevent front and rear low speed collisions.




Available driver assistance features on the trucks include Forward Collision Alert and Lane Departure Warning.


Forward Collision Alert is a warning system only and does not apply the brakes. The system may help to avoid or reduce the harm caused by front-end crashes by detecting vehicles within a distance of approximately 197 ft. (60 m). It operates at speeds above 25 mph (40 km/h). If the vehicle approaches another vehicle too rapidly, a warning symbol will flash and beeps will sound. To change the alert timing (Far, Medium, Near, or Off), press the Forward Collision Alert button on the steering wheel.


The Lane Departure Warning system is designed to help avoid crashes due to unintentional lane departures. The system uses a camera sensor on the windshield ahead of the rearview mirror to detect the lane markings. It operates at speeds of 35 mph (56 km/h) or greater. When a detected lane marking is crossed without using a turn signal in the lane departure direction, a warning symbol illuminates on the instrument cluster. The system can be turned on or off using the Lane Departure Warning button on the instrument panel.


If the Forward Collision Alert or Lane Departure Warning systems do not seem to operate properly, clean the front of the vehicle and the outside of the windshield in front of the camera sensor.


Depending on options, additional vehicle performance enhancement systems are available, including:

• Hill Descent Control System

• Hill Start Assist

• Trailer Sway Control

• Tow/Haul Mode

• Automatic Locking Rear Differential




The four available radio options are:

• 4.2-inch (107 mm) color non-touch display system (RPO IO3)

• 4.2-inch (107 mm) color non-touch display with MyLink™ or IntelliLink™ connectivity (RPO IO4)

• 8-inch (203 mm) color touch screen display with MyLink or IntelliLink connectivity (RPO IO5)

• 8-inch (203 mm) color touch screen display with MyLink or IntelliLink connectivity and embedded navigation (RPO IO6) (Fig. 6)


2015 GMC Canyon Interior Detail

Fig 6


The trucks also offer optional OnStar® 4G LTE with a built-in Wi-Fi hotspot that supports up to seven mobile devices.


TIP: To retrieve the SSID and password for the hotspot, press the OnStar Voice Command button and say “Wi-Fi settings.” The information will be displayed on the infotainment screen.


Extended Cab Rear Seat Cushion Extension for Child Restraints


The Colorado and Canyon Extended Cab models are equipped with a rear seat head restraint that can be used as a seat cushion extension for installation of a child restraint in the rear passenger-side seat. By removing the head restraint and attaching it to the front of the seat cushion, with the notch on the posts facing outboard, it provides for additional support for a child restraint. (Fig. 7)


F07 cc rear seat extension

Fig 7


Climate Controls


The HVAC blower motor is a brushless design that uses Back Electromagnetic Field (EMF) to control operation. An electromagnetic field (EMF) is a physical field produced by electrically charged objects. It affects the behavior of charged objects in the vicinity of the field.


The back EMF method requires that current flows through the motor windings at a sufficient level in order to function without error. During this start-up phase, the motor performs some critical functions while spinning the rotor up from 20 rpm to 450 rpm in order to get a sufficient current generated, which allows the rotor position to be synchronized with the magnetic field rotation. Once this occurs, the motor starts its ramp up.


TIP: Due to EMF operation, the HVAC blower motor has a five second delay on start up after manually adjusting the power knob from Off to On. It’s important that customers understand that is a normal operating characteristic of the climate control system.


Special Tools


The following new tools were released for the 2015 Colorado and Canyon:

Screen Shot 2014-09-18 at 11.07.01 AM


– Thanks to Charles Hensley and Sherman Dixon


Appearance of the Truck Bed Rails

After installing accessories on the bed rail caps on the 2015 Colorado and Canyon, it may be noticed that the bed rails are not as wide at the rear of the pickup bed as they are at the front of the bed. This may typically be noticed after the installation of GM Accessory Soft Folding or Soft Roll-Up Tonneau Cover rails. It may appear that the accessory installation was incorrect or that parts of the accessory kit may be damaged.


The changing width of the bed rail cap is by design and part of the sleek appearance of the truck; no repairs are necessary to correct it.


Because the bed rail caps narrow as they go toward the rear of the vehicle, and the tonneau cover rails maintain a rectangle shape, the narrowing of the bed rail caps is highlighted and more noticeable. (Fig. 8) Do not attempt to repair or replace parts for this condition.


F08 bed rail width

Fig 8


– Thanks to Jeremy Richardson

Front Passenger Floor Water Leak

After a hard rain or large amounts of melting snow, a water leak may be noticed on the front passenger floor of some 2011-2015 Cruze models. This condition may only be evident when the vehicle has been parked on an incline and may be caused by water running down the windshield, under the air inlet grille panel and entering the body air inlet of the HVAC system.


To prevent water leaking onto the front passenger floor, install an air inlet deflector over the HVAC air inlet.


First, remove the passenger-side air inlet grille panel and clean the surface around it (Fig. 9) where it will contact the air inlet deflector with LORD Fusor 703 Adhesion Prep/Cleaner or equivalent.


TIP: Trial fit the deflector to see where the adhesive will bond with the part.


F09 air inlet

Fig 9


Next, spray a light coat of LORD Fusor 602EZ Surface Modifier or equivalent to the panel and air inlet deflector. Allow a minimum of 10 minutes for the surface modifier to dry.


Prepare the LORD Fusor 143 Plastic Repair Adhesive or equivalent using the appropriate applicator and mixing nozzle. Apply a 1/4-inch to 3/8-inch diameter bead of adhesive above the foam around the backside of the deflector. (Fig. 10)


F10 air deflector adhesive

Fig 10


Install the deflector over the HVAC air inlet and hold it firmly in position for one minute. (Fig. 11)


TIP: Once the adhesive has been purged from the mixing nozzle, working time is about one minute. Be sure to have the deflector near the HVAC air inlet and apply the adhesive immediately for proper installation.


F11 air deflector installed

Fig 11


For more information, refer to #PI1302.


– Thanks to Steve Bruder

Fuel Gauge Operation

There may be some questions from owners about fuel gauge operation on 2013-2015 Acadia, Enclave and Traverse models. (Fig. 12)


F12 fuel gauge image

Fig 12


The fuel gauge will read full when there is 19.8–21.8 gallons (75–82.5 L) in the fuel tank. When the fuel tank is more than 15 percent full, the ECM uses the signal circuit of the fuel level sender to calculate the remaining fuel level percent in the fuel tank.


Once the fuel level drops below 15 percent, the ECM switches to a Low Volume Fuel Consumption mode and stops using the fuel sender reading. The remaining fuel level is calculated based on fuel injector pulses. This is done to reduce gauge fluctuation due to sloshing fuel.


When refueling the vehicle, enough fuel must be added to bring the fuel level to 18 percent or more in order for the system to exit Low Volume Fuel Consumption mode. If only a small amount of fuel is added and the fuel level does not reach 18 percent, the fuel gauge needle will not move.


TIP: The fuel level must be more than 8 percent in order for the Remote Start system to operate.


On 2013-2014 models, the low fuel warning message displays when there is approximately 1.7 gallons (6.4 L) left in the fuel tank. The range accuracy for miles remaining depends on driving conditions. For example, steady driving with the fuel level below a quarter tank tends to average higher remaining miles than stop-and-go driving. The miles to empty fuel range reading should not be relied upon as an absolute indication.


To help address this situation on 2015 models, the low fuel warning message will display when there is approximately 2.5 gallons (9.5 L) left in the fuel tank.


During fuel system diagnosis, the fuel system can be forced into fast filtering mode by driving the vehicle at more than 2 mph (3.2 km/h), and then placing the shift lever into Park or Neutral for more than 45 seconds. After 45 seconds, the system will command the fuel gauge to display the current fuel level.


– Thanks to Gary McAdam

Repeat Service 4WD Message

Some 2014 Silverado and Sierra trucks and 2015 Tahoe, Suburban, Yukon and Escalade models equipped with four-wheel drive (RPOs NQH, NP0) built prior to September 7, 2014 or that have had the Transfer Case Control Module (TCCM) reprogrammed prior to September 7, 2014 may have a repeat Service 4WD message and one or more of the following DTCs set: C0398 (Range Actuator Position – Range Position Correlation), C038D (Range Actuator – Position Not Learned) or C0397 (Transfer Case Clutch). Typically, DTCs C038D and C0397 will be set together or DTC C0398 will be stored in the TCCM.


There also may be a binding feeling from the drivetrain on turns. If the vehicle sets a DTC in Auto 4WD mode, the default action is to move the encoder motor to apply the clutch pack, and then disable all further shifting. If this occurs, the driver may then move the transfer case shift knob to 2WD, but since shifting is disabled due to the set DTC, the vehicle may arrive at the dealership with a binding on turns condition with the shift knob in the 2WD position. (Fig. 13)


2014 GMC Yukon Interior

Fig 13


To correct these conditions:


• If the vehicle has DTC C038D and C0397 set, reprogram the TCCM with the latest software available through TIS2Web. Perform a high-low clutch reset and shift the transfer case through all ranges, ensuring that no DTCs reset and that the transfer case shifts through all ranges as expected. If all shifting is successful, return the vehicle to the customer.


• For vehicles equipped with RPO NQH, if DTC C0398 sets after being dinghy towed, refer to #PIP5217.


• If the vehicle has DTC C0398 set, inspect circuits 7477, 7478, and 7479 for any terminal or connection issues between the B2227 Gear Position Sensor and the TCCM. (Fig. 14) Repair any terminals or connectors as needed. If there are not any wiring concerns, clear the DTC and reprogram the TCCM with the latest software available through TIS2Web. Perform a high-low clutch reset and shift the transfer case through all ranges, ensuring that no DTCs reset and that the transfer case shifts through all ranges as expected. If all shifting is successful, return the vehicle to the customer.


F14 transfer case controls

Fig 14


TIP: Reprogramming the TCCM on any vehicles built on or after September 7, 2014 will not correct any conditions. Follow the appropriate Service Information for the stored DTCs.


– Thanks to Steve Schipansky and Dave Peacy

Outside Air Temperature Sensor Operation

The Outside Air Temperature (OAT) sensor on the 2013-2015 ATS and 2014-2015 CTS Sedan (Fig. 15) uses a filter routine to minimize false updates due to engine heat or road heat.


F15 CTS OAT screen

Fig 15


These readings are based on the following:

• If the vehicle is parked more than two hours, the OAT updates to the current sensor reading.

• If the vehicle is parked less than two hours and the new reading is LESS than the vehicle shutdown reading, the OAT updates to the current sensor reading.

• If the vehicle is parked less than two hours and the new reading is MORE than the vehicle shutdown reading, the vehicle will start up with the shutdown reading. As the vehicle is driven at speeds over 19 mph (30 km/h), the filter counter starts to count up; at speeds under 19 mph (30 km/h), the filter counter starts to count down. Once the counter reaches its maximum count, the previous OAT reading is updated to the current OAT reading.


For example, the vehicle is off for one hour and the OAT shutdown reading is 70°F (21°C). While the vehicle is parked, the outside temperature increases to 74°F (23°C). When the vehicle is started, the OAT reading will still be clamped at 70°F (21°C). If the vehicle is driven at a stable speed over 19 mph (30 km/h) for a minimum of 3–8 minutes with no stops, the OAT reading updates to the current temperature of 74°F (23°C). However, if the vehicle is driven in heavy stop-and-go city traffic for 10 minutes before entering the highway for a minimum of 2–6 minutes, it will take longer for the OAT reading to update to the current temperature of 74°F (23°C) because of the driving at slower speeds.


Since the OAT sensor is in the front grill, the values must be filtered to prevent them from updating to false readings when there is engine heat or road heat.


If the vehicle is started in a garage that is warmer than the outside temperature, it may take up to 10 minutes to update to the new cooler ambient temperature.


For example, the vehicle is off for a short time or overnight in a garage with a constant temperature of 70°F (21°C). While the vehicle is parked, the outside temperature decreases to 60degF. When the vehicle is started, the OAT reading will register 70°F (21°C) (the garage temperature). When driven outside, the OAT reading will start to update to the lower 60°F (16°C) temperature as the sensor cools off. This should take less than eight minutes; or less than 10 minutes if the vehicle is driven at slower stop-and-go traffic.


– Thanks to David Antal


Body or Suspension Noise while Driving over Bumps

On some 2011-2015 Camaro Convertible models, an intermittent creak or pop noise may be heard coming from the underside of the vehicle while driving over bumps.


If a confirmed noise from the undercarriage of the vehicle cannot be clearly isolated, check that the mounting fasteners of the vehicle’s various cross-braces have been torqued properly. There are a total of six braces with a combined 26 fasteners that will require inspection. All fasteners called out in the following photos should to be torqued to 43 lb-ft (58 Nm).


If a fastener is found not torqued to specification, remove the fastener, clean the applicable threads, and apply medium-strength (blue) threadlocker. Reinstall the fastener and torque it to the required value. Confirm that the noise(s) have been eliminated.


Braces 1 and 2 are the front end lower structure braces (left brace shown). (Fig. 16)


F16 3971569

Fig 16


Brace 3 is an underbody brace. (Fig. 17)


F17 3971567

Fig 17


Brace 4 is another underbody brace. (Fig. 18)


F18 3971568

Fig 18


Braces 5 and 6 are the underbody side rail cross braces. (Fig. 19)


F19 3971571

Fig 19


Refer to #PIC6022 for more details and parts information.


– Thanks to Matt Bierlein

Supercharger Rattle Sound

On some 2014 CTS-V and Camaro models equipped with the 6.2L engine (RPO LSA), and some 2009-2013 CTS-V and Camaro models equipped with the 6.2L engine (RPO LSA) that have had a service replacement supercharger installed after November 2013, a flutter or buzz sound may occur at 800-900 rpm (low rpm) with the vehicle in 2nd or 3rd gear (high load). The sound may be mistaken as clutch chatter or a heat shield buzzing noise.


The supercharger now has a solid coupling for improved reliability. Pulses from the accessory drive at low rpm, high load may cause a slight rattle in the supercharger gear train. This is normal condition. No repairs should be made for this condition at this time.


– Thanks to Richard Renshaw

Corvette Performance Data Recorder

The 2015 Chevrolet Corvette Stingray (Fig 1) is offering an industry-first factory-installed, integrated Performance Data Recorder (PDR). The PDR, developed by Cosworth Engineering, the British motorsports-engineering company that supplies telemetry for the Corvette Racing team, enables drivers to record high-definition video, with telemetry overlays, of their driving experiences. (Fig. 2)


2015 Chevrolet Corvette Stingray

Fig 1


The PDR is available as an option on any 2015 Corvette Stingray equipped with the navigation system. It will appeal to drivers who wish to improve their driving skills through studying and analyzing results as well as those who want to share their driving experiences with others on the web.


F02 PDR 1

Fig 2


The recorded video can be reviewed immediately in-car when parked or downloaded to a personal computer.


Click below to see the PDR in action. (Fig. 3)


F03 PDR footage 1

Fig 3






The PDR consists of three components: a high-definition (HD) camera, telemetry recorder and a dedicated SD-card slot.


The HD camera, integrated with the rearview mirror, captures the driver’s point-of-view through the windshield, and sound is captured with a dedicated microphone.


The telemetry recorder obtains data from two sources. First a dedicated GPS receiver operates at 5 hertz, five times faster than a typical in-dash navigation system. The recorder is hard-wired into the Stingray’s Controller Area Network, or CAN, to access 30 channels of vehicle information, ranging from engine speed and transmission-gear selection to braking force and steering-wheel angle.


The dedicated SD-card slot is located in the glove box. It provided the capability to record and transfer video and vehicle data. An 8 GB card can hold approximately 160 minutes of video and data, while a 32 GB card stores up to 800 minutes — more than 13 hours of driving time.


Telemetry Overlays


Depending on the data desired, the driver can choose to overlay the driving video with four different levels of information.


The Sport Overlay includes key vehicle data, such as speed, gear position, RPM and lateral G-forces. (Fig. 4)


F04 PDR sport mode

Fig 4


The Track Overlay adds GPS tracking map and brake/throttle application. This is the maximum information overlay. (Fig. 5)


F05 PDR track mode

Fig 5


The Performance Timer overlay provides performance metrics, including 0-60 mph (0-100 km/h) time, 0-100 mph (0-200 km/h) runs and 1/4-mile (400 m) time. (Fig. 6)


[INSERT FIG 6]F06 PDR performance timer

Fig 6


And finally, the Tour Mode provides video and audio with no data overlay. (Fig. 7)


F07 PDR tour mode

Fig 7




There are several choices for playing back and reviewing the recorded data.


The driver can view the data on the car’s 8-inch (203 mm) color touch screen when the vehicle is parked.


The SD card can be removed from the car and plugged into a computer for viewing.


In addition, the SD card can be used to drive the Cosworth Toolbox, an included application that provides a number of viewing options and data analysis.


The Cosworth Toolbox includes:

• Stats Page – Allows comparison of lap-to-lap data.

• Video Plus Data – Permits comparing acceleration, braking, and steering angle to aid in improving lap-to-lap performance.

• Corners Page – Provides a satellite map of the track with displays of maximum speed, gear number, steering angle and gain/lose comparisons. (Fig. 8) This permits the driver to visualize driving inputs as they relate to specific portions of the road or track being driven.


F08 PDR corner

Fig 8


Click below to see how these tools were used by several driver’s on a closed course in the PDR Track Challenge. (Fig. 9)


F09 PDR footage 2

Fig 9



Valet Mode


The PDR also works with the Valet Mode, which allows drivers to lock the interior storage, disable the infotainment system and record video, audio and vehicle data by entering a unique four-digit code on the infotainment touch screen. (Fig. 10) With Valet Mode activated, any vehicle activity is recorded while the owner is away from the vehicle.

Chevrolet Corvette Valet Mode


– Thanks to Jeff Strausser

Vibration Diagnosis

Vibration Diagnosis


Vibrations must be diagnosed carefully — there may be multiple causes for the same symptom — whether its related to wheel/tire concerns, propshaft imbalance or other conditions. (Fig. 11) The correct diagnostic equipment must be used, and it must be used properly. “Seat of the pants” diagnosis is not satisfactory.


F11 propshaft

Fig 11




Vibration: A vibrating object undergoes a change in position that repeats at regular intervals and whose direction of movement changes at the same regular intervals.


Cycle: A vibrating object makes one complete trip, from starting point to one extreme, back past the starting point to the other extreme, then back to the starting point


Frequency: The amount of time it takes for the vibrating object to make one cycle (expressed in cycles per second, or Hertz)


Amplitude: The distance the vibrating object moves during a cycle (peak to peak)


Orders of Vibration (of revolving component):

• First (1st) order vibration — frequency of once per revolution

• Second (2nd) order vibration — frequency of twice per revolution

• Third (3rd) order vibration — frequency of three times per revolution

• Etc.




Systematic customer questioning will help in clearly understanding the customer’s concern and will help focus attention on the relevant part of the vehicle.


Determine what type of disturbance is causing the customer concern.

• Is it a noise or a vibration?

• When was it first noticed?

–       When the vehicle was new

–       After an event, such as an accident

–       Gradually

• Under what conditions does the disturbance occur?

–       Road texture

–       At speed

–       During speed changes

–       Loaded or unloaded

–       Transmission shifting

–       When an accessory is turned on or off

• Where is the disturbance felt?

–       In a seat

–       In the steering wheel

–       In the floor




Using the information gathered from the customer, perform a preliminary inspection of the suspected area.


Wheels and Tires


Look for anything that could change balance, runout, or both, which could cause vibration.


On wheels, look for missing balance weights, missing or loose lugnut(s), gouges, or mud or dirt deposits.


Check tires for foreign objects in the tread, missing chunks of tread, bulges, flat spots, abnormal wear, or incorrect pressure.


TIP: If wheels or tires are not OEM or a dealer-installed GM Accessory, the customer will need to return to the point of purchase for resolution.




Look for missing weights, excessive runout, U-joint wear, a bent or dented shaft, and missing or loose U-joint fasteners.


Shock Absorbers


Look for damage, leaks, or loose fasteners. A leaking shock absorber is probably worn, which can contribute to vibration.


Exhaust System


Inspect the system for damaged or missing hangers, or pipes grounding against a body or frame component. Rattles, pops, buzzes or whistles may result from an improperly installed or loose muffler baffle.




A worn or damaged mount can allow the powertrain to move unnecessarily.


Loose or Excessive Loads


Look for heavy or loose objects inside the body or in the cargo bed. Excessive loads can change the vehicle’s ride height, leading to driveline angle-related vibrations.


Road Test


Perform a road test to simulate the conditions described by the customer. Operate the vehicle under various conditions: different road surfaces, speeds, coastdown, turns, gear changes, gear ranges, and engine speeds.


Observe whether the disturbance is related to wheel speed or engine speed.




CH-51450 Oscilloscope Diagnostic Kit with NVH


Traditional diagnostic methods require you to determine the frequency of the vibration (Hertz) during a road test, and then to figure out which component was rotating at the RPM necessary to cause the frequency observed. This requires directly measuring the dimensions of various components, or looking up dimensions in specification charts and applying mathematical calculations to arrive at a conclusion.


The CH-51450 Oscilloscope Diagnostic Kit with NVH (Fig. 12) provides a more accurate analysis of vehicle noise, vibration and harshness conditions. Using the display of your existing laptop computer, this system combines fast capture and analysis of vehicle data with a clear easy-to-read presentation of results and actions.


F12 CH-51450

Fig 12


The real-time diagnosis of the CH-51450 is presented as a bar graph, a frequency chart, a 3D frequency chart, RPM order or a road speed view.


During diagnosis, the recording can be started before a road test, and then played back for analysis after returning to the dealership. It’s easy to save the file to the laptop’s hard drive.


The kit detects multiple vibrations and noises, and accurately isolates the source of vibration or noise related to tires, wheel assemblies, engine, drivetrain and engine accessories.


Direct connection to vehicle data communication provides vehicle speed, engine speed, driveshaft speed, and wheel speed at a given road speed to correlate different sources of vibration. It works with the Multiple Diagnostic Interface (MDI) or any J-2534 interface to acquire vehicle data. No technician calculation of vibration is required.


In addition, the customer report function can be helpful to explain the diagnosis and repairs that have been made.


GSP9700 Vibration Control System


The GSP9700 (Fig. 13) is a precision instrument which performs wheel and tire measurement and balance operations. It requires proper training for successful results.


F13 gsp9700

Fig 13


Here are some of the procedures it can accomplish, with relevant definitions.


Runout is a term that applies both to wheels and tires separately, and also applies to the combination when the tire is mounted to the wheel. Runout refers to the variation in roundness, or change in distance from the center of the tire outward to the tread, as the tire is rotated.


Radial Runout is a condition in which the tire and wheel assembly is slightly out of round, forcing the spindle to move up and down as the vehicle rolls along a smooth surface.


Lateral Runout is the amount of side-to-side movement as the tire/wheel assembly rotates. It is the variation in sidewall geometry while inflated, loaded and rotating.


Radial Force Variation is the vertical force between the tire and the road (or loadwheel on the balancing machine). The radial axis is perpendicular to the road. This is the axis where radial force is applied to the tire. Once the tire is inflated, loaded and rotating, the radial force becomes periodic.


Lateral Force is the side-to-side force along the rotation axis between the tire and the road (or loadwheel of the balancing machine). The lateral axis is where side-to-side forces are applied to steer the vehicle. Once the tire is inflated, loaded and rotating, the lateral force variation becomes periodic.


Tangential Force is the driving force between the tire and the road (or loadwheel on the balancing machine.) The tangential axis is parallel to the road, in the direction of travel. This is the axis where the driving force is applied to the tire.


Dynamic Imbalance is defined as one or more locations of the tire/wheel assembly being heavier, causing an imbalance force and/or an imbalance wobble.


For instance, a tire/wheel assembly has two heavy spots of equal weight which are located 180 degrees radially from each other on opposite sides. As this assembly rotates, centrifugal forces cause a large imbalance wobble to be created, but the imbalance force (as well as the static imbalance) will be zero. A wheel with this condition will cause a wobble or shimmy to be felt in the steering wheel.


Modern dynamic balancers spin the wheel in order to measure both the up and down imbalance force and the wobble or shimmy related imbalance (side-to-side).


Dynamic balancers direct the operator to place correction weights on the inside and outside correction locations of the rim so that both imbalance force and imbalance wobble will be eliminated.




If tires are suspected, swap tires from a known-good donor vehicle. Be sure to qualify the tires on the donor vehicle before swapping. This includes making sure the tires have 10-15 miles (16-24 km) on them to remove temporary flat-spotting.


Be sure to drive the donor vehicle before swapping tires to be sure the donor does not exhibit the same condition. It is also advisable that the donor vehicle have the same axle ratio as the customer vehicle, to limit variables.


When mounting tires, use the lubricant specified in Bulletin 12-03-10-001 and apply it as directed. Excessive lubricant, the wrong lubricant, or improper application can cause the tire to slip on the wheel during acceleration and braking. It helps to mark the tire/wheel relationship on the inboard side of the assembly so that any slippage can be noted. DO NOT use silicone or other products that are not designed specifically as tire mounting lubricants.


If tires are ruled out, check propshaft runout. If propshaft imbalance is quite high, re-indexing the shaft may reduce imbalance.


If ring and pinion runout is suspected, be sure to clean lubricant from the gears before taking backlash measurements. Lubricant can affect clearance, which could lead to misdiagnosis.


If swapping a propshaft, an on-vehicle balance also may be necessary to eliminate a vibration condition. Check the appropriate Service Information for the correct specifications. For example, in earlier model year full-size trucks, a balance of 20-40 gram/centimeters was usually not felt by the driver. For the current full-size trucks (2014 Silverado and Sierra 1500 pickups, and all 2015 full-size pickups and SUVs), about 5-10 gram/centimeters is required to be acceptable.


On full-size trucks with a 3.08 axle ratio, a tire with a 3rd order harmonic vibration can masquerade as a 1st order driveshaft issue. This 3rd order vibration can combine with the 1st order driveline vibration to create a phasing vibration (a vibration that seems to increase and decrease in amplitude at a steady speed). The correction is to make the 1st order vibration as low as possible to eliminate the phasing boom.


A propshaft runout of 0.020-inch or less is required to satisfy a sensitive full-size truck owner.


Adjusting the U-joint working angles on the current full-size trucks is normally accomplished by moving the center bearing up and/or shimming the axle pinion up about 2 degrees. It is generally not necessary to move the transmission up or down.


– Thanks to Dave MacGillis and Peter Joslyn


Squeak Noise When Closing the Door

A squeak-type noise may be heard when closing the door on some 2010-2015 Camaros. The noise may be coming from the door weatherstrip that is attached to the body. (Fig. 14) It will only be heard for a brief moment when the door is actually being closed.


The noise is caused by the weep holes in the weatherstrip being partially blocked. These weep holes are located around the length of the weatherstrip to allow moisture and air to escape. If these holes are partially blocked by debris or even a small piece of foam that was not fully punched out all the way, a “poof” noise may be heard in some instances while the door is closing.


2015 Chevrolet Camaro with available 1LE Package Fig 14


To correct this condition, make sure the weep holes are free and clear of debris. It is also acceptable to add an additional weep hole in the bottom of the weatherstrip using an awl. If this is required, be sure to make this additional hole in an inconspicuous location so it will not be visible to the customer.


– Thanks to Matt Bierlein

Sticking Camshaft Position Actuator Solenoid Valve

On some 2014-2015 Corvette, Silverado, Suburban, Tahoe Sierra, Yukon, and Yukon XL models equipped with a 4.3L, 5.3L or 6.2L engine (RPOs LV3, L83, L86, LT1), an intermittent crank, no start condition may be present with DTCs P0011 (Intake Camshaft Position System Performance) and/or P00C6 (Fuel Rail Pressure Low During Engine Cranking) set.


The engine may sound like it is cranking fast and actual fuel rail pressure may be low. A compression test may show lower than expected readings and exhaust flow from the tailpipe may be noticeably lower while cranking when compared to a known good vehicle. The fuel rail pressure sensor may show 300–400 PSI (2,068-2,758 kPa) and will slowly drop into the 50 PSI (345 kPa) range while cranking.


The camshaft position actuator solenoid valve may be sticking or binding and causing the valve timing to be retarded.


Before removing the camshaft position actuator solenoid valve, use calipers to measure the height of the center portion (called the spool) to the outer body. Do not apply force or pressure on the center portion. A stuck valve will measure less than 6 mm.


If a stuck valve is found, replace the camshaft position actuator solenoid valve. (Fig. 15)


If the concern is an intermittent no start or crank, no start condition, record the depth of the plunger and replace the camshaft position actuator solenoid valve.


F15 actuator valve

Fig 15


TIP: The camshaft position actuator solenoid valves must be kept parallel to the engine front cover during removal and installation. The camshaft position actuator solenoid valves can be damaged if they become wedged or stuck during this process.


– Thanks to Richard Renshaw


Inspect Terminals for DTCs P00C6, P228C

If normal Service Information diagnostics do not lead to a repair when DTCs P00C6 (Fuel Rail Pressure Low During Engine Cranking) and/or P228C (Fuel Pressure Regulator Control Performance – Low Pressure) are set on a 2010-2014 LaCrosse, CTS, SRX, Equinox, Terrain; 2013-2014 ATS, XTS; 2012-2014 Camaro, or Impala equipped with the HFV6 engine (RPOs LF1, LFW, or LFX), check the terminals at the ECM for fit and tension as well as the crimp to wire connection before replacing any components.


Terminals to inspect in the E39 and E39A controllers are:

• Connector x2 terminals 3, 18, and 19 for the fuel rail pressure sensor. • Connector x3 terminals 16 and 32 for the high pressure fuel pump. (Fig. 16)


F16 pin 16

Fig 16


TIP: As little as 2 Ohms on either circuit can cause these DTCs to set.


If any conditions are found, replace the affected terminals and verify the vehicle is repaired.


– Thanks to Aron Wilson

CHMSL Wiring for Aftermarket Bed Cap

When installing an aftermarket bed cap or topper on a 2014 Silverado 1500 or Sierra 1500; or a 2015 Silverado or Sierra, the wiring provisions for the Center High Mounted Stop Lamp (CHMSL) are provided at the Rear Body Junction Block (X63A) connector X6, terminal 1.


Follow the installation guidelines based on the vehicle configuration.


With the Under Rail Bed Lighting Option


Trucks equipped with the under rail bed lighting option will already have an X6 connector at the Rear Body Junction Block X63A. (Fig. 17) Obtain an appropriate length of 14 gauge wire to run from the Rear Body Junction Block up to the CHMSL wiring for the cap or topper. Create a terminated lead using terminal part #828905-1 in Lear Tray 16, along with wire seal part #1-968857-3 in Lear Tray 7 and connect to one end of the wire.


Disconnect the X6 connector at the Rear Body Junction Block and remove the rubber cavity plug in terminal position 1 and discard. Install the terminated lead into the X6 connector terminal 1. Run the wire up to the CHMSL for the cap or topper and connect. The ground for the cap or topper CHMSL will need to be made to an appropriate ground.


F17 junction block x6

Fig 17


Without the Under Rail Bed Lighting Option


Trucks not equipped with the under rail bed lighting option will have a dummy connector at the X6 position of the Rear Body Junction Block. The X6 connector body is not available separately, but can be obtained by ordering the under rail bed lighting harness (GM part number 22878806). The harness includes terminals/wiring in positions 4 and 7. Remove the wiring from terminal 4 and discard. Move the rubber cavity plug from terminal position 1 into terminal position 4.


Obtain an appropriate length of 14 gauge wire to run from the Rear Body Junction Block up to the CHMSL wiring for the cap or topper. Create a terminated lead using terminal part #828905-1 in Lear Tray 16 along with wire seal part #1-968857-3 in Lear Tray 7 and connect to one end of the wire. Install the terminated lead into the X6 connector terminal 1. Terminal 7 is a ground circuit used for the under rail bed lighting and it can be used to ground the CHMSL for the cap or topper, if desired. If terminal 7 is not used, remove the terminal and install a rubber cavity plug or cut off the additional wiring, leaving a couple inches of wire, and seal the end of the wire.


– Thanks to Jim Will

Securing Chrome Center Caps

On some 2015 Silverado 2500/3500 and Sierra 2500/3500 models equipped with chrome or polished aluminum wheels (RPOs PYS, RQ9, PYV, PYR), the center caps on the wheels (Fig. 18) may be missing or may have come off while driving.


F18 center cap

Fig 18


To prevent this condition, check that all center caps are secure by pressing the chrome center cap onto the wheel until an audible “click” is heard. After installed, perform a pull test to verify the cap is secure. The cap should not come off by hand from the front of the wheel.


To properly remove the cap, press it off from the back of the wheel.


– Thanks to Kenneth Cole

Loose Rear Body Fuse Block Connection

When working on the any of the following systems: liftglass, liftgate release, power liftgate, rear HVAC blower, 2nd row flip and fold seats, heated outside mirrors, rear heated seats, or rear wiper, which receive power from the Rear Body Fuse Block on 2015 Escalade models, Suburban, Tahoe, or Yukon models, inspect the fuse for a loose connection inside the fuse block itself. (Fig. 19) In some cases, the fuse has poor terminal tension and may cause intermittent or completely inoperative conditions for these systems.


F19 3972411

Fig 19


TIP: Disconnect the negative battery cable when performing this procedure.


Using the “purple” J-35616-35 test probe, check for proper terminal tension at the suspect fuse. (Fig. 20)


F20 3972412

Fig 20


If poor terminal tension is found, first remove all the fuses and relays from the fuse block. Next, remove the white cover from the Rear Body Fuse Block by releasing the three retainers on the sides and bottom. (Fig. 21)


F21 3972413

Fig 21


In many cases, the loose connection is on the main power buss bar inside the Rear Body Fuse Block. (Fig. 22)


F22 3972414

Fig 22


Using a pair of long nose pliers or a similar tool, adjust the buss bar fuse terminal. (Fig. 23) Retest the terminal tension using the test probe and readjust if necessary until proper tension is achieved.


F23 3972416

Fig 23


– Thanks to Jim Will

Service Know-How

10214.09D – Emerging Issues

September 11, 2014


To view Emerging Issues seminars:

• Log in to

–   Select Resources, and then Video on Demand; or

–   Select Catalog to search for the course number, and then select View > Take or Continue Course

Car Issues – Fix It Right the First Time

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Truck Issues – Fix It Right the First Time

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