Archive for April 2014

New 15-Digit Battery Warranty Code

A warranty code is required for all batteries replaced under warranty. The code is generated by the Midtronics GR8 Battery Tester/Charger (EL-50313), which now captures additional information in the expanded 15-digit code. The software of the tester/charger must be updated. The latest software release is available on the GM Dealer Equipment website (U.S.) at In Canada, go to


Warranty codes are generated only when the battery test is set up as follows on the tool:

• Select Diagnostic Mode

• Select Out Of Vehicle

• Replace decision is the test result


The15-digit code (17 digits when counting the two hyphens) is labeled Warranty Code on the printed slip. (Fig. 1) The complete 15-character code must be entered into the Labor Code Dependency Field in GWM. The code under the words MID INFO is NOT a valid warranty code.


F01 GR8 ticket 15 digit code

Fig 1


TIP: Before shipping a battery being returned under warranty, check for the correct battery part number on the top of the battery. The battery part number must match the vehicle application for the warranty claim.


Software Updates


Dealerships were asked to update the EL-50313 software by December 1, 2013. For repairs performed after this date, the previous level software warranty codes will no longer be valid.


The revised software includes provisions to test the new Stop/Start Auxiliary battery found in some new products.

Check for software updates regularly. There are unique downloads for the U.S. and Canada.


To access downloads on the GM Dealer Equipment website, a user name and password must first be registered. A link is provided below the sign-in area to “Apply for Access.” If assistance is needed, contact GMDE at 1-800-GM-TOOLS (1-866-868-3372 in Canada).


Battery Test Results


When testing batteries, follow the instructions on the tester/charger screen. Select “Out Of Vehicle” when setting up the test.


It is not necessary to remove the battery from the vehicle, but the vehicle battery cables must be disconnected and the tool cable clamps connected directly to the battery posts. The battery terminal posts are the only reliable connection points.


PDI Mode


The EL-50313 tester/charger has a charge algorithm identified on the tool as PDI Mode. In this mode, the battery condition is checked, and then a fast charge is applied to the battery. This mode is designed to apply as much charge as safely possible in 20 minutes.


PDI Mode replaces the previous requirement of battery voltage check and charge. This mode also generates a printout. The printout must be kept with the vehicle file as proof of maintenance.


TIP: On vehicles with two batteries, each battery must be electrically isolated and charged individually, which will result in two printouts.


For additional information about battery warranty codes and labor operations, refer to Bulletin #03-06-03-004K.


– Thanks to Gary McCraw



Take the 2014 TechLink Reader Survey

At TechLink, our goal is to provide the latest GM technical news and repair information to help you quickly and accurately repair the vehicles that come into your service department every day.


We typically cover a wide range of topics, from the latest diagnostic and technical repair information to Techline programming, new model features, special tools and more.


We would like your thoughts on how we’re doing. We’d like to hear from technicians and other service department professionals about the types of repair information to cover and which new topics are of interest and value. Your input will help in determining the coverage of future editions.


F02 survey


Click the survey above or the Survey link on the right side of the home page to take a short survey about the information you want most in TechLink. The survey will be available until the end of May.


Your input is very important to us. Thanks for taking the time to complete the survey. We’ll share the results when the survey is complete.


– Thanks to Lisa Scott


Lamp Damage and Lamp Condensation

Cracks, chips, scratches, breaks and other damage to headlamps, tail lamps and other exterior lights are often the result of an impact with a road hazard or improper maintenance. These conditions are not covered under the GM New Vehicle Warranty. Two bulletins have recently been updated recently regarding lamp damage (Bulletin #02-08-42-001F) and lamp condensation (Bulletin #01-08-42-001I).


Chemical Damage


On most late model vehicles, headlamp and license lamp lenses are made of polycarbonate, due to its high temperature and impact resistance. Polycarbonates can be damaged, crazed or cracked by improper contact with various chemicals (Fig. 3):

• Cleaners used to remove rail dust

• Rubbing compounds

• Grease/tar/oil removers

• Tire cleaners

• Prep solvents

• Cleaners/waxes

• Undiluted washer solvent

• Alcohol

• Concentrated car wash soaps


F03 lamp chrome cleaner

Fig 3


Only lukewarm or cold water, a soft cloth and car washing soap should be used to clean exterior lamps and lenses.


Overheating Damage


Overheating most often appears as imperfections in the lens surface. This results from restricting the amount of heat that the lamp can dissipate.


Avoid covering headlamps with shop mats or fender covers if the vehicle is being serviced with the headlamps or DRLs illuminated. This can cause crazing and deformation due to overheating; the results may be immediate or may eventually appear as hairline cracks.


Another trend being seen is the installation of headlamp or fog lamp bulbs that have a higher output than the original equipment. Because the bulb output is higher, the operating temperature is also higher. This excessive heat can melt the socket, housing, or lens. The bulb number should match the GM service part.


Impact Damage


Impact damage is often indicated by the assembly holding moisture, being inoperative, or blemished.


Polycarbonate headlamp lenses are very tough and will withstand normal stone strikes without damage. They are also tough enough not to show witness marks of impacts severe enough to damage the rear housing. This damage is often revealed through close visual inspection once the lamp is removed. Broken mounting tabs, rear housing fractures, (Fig. 4) and loose components inside the lamp assembly are evidence of impact damage.


When encountering these concerns, never assume it will automatically be a warranty repair. Inspection of the lamp assembly, once removed from the vehicle, is required to assess warrantability.


F04 lamp housing crack

Fig 4


Lamp Condensation


A distinction is made between a lamp with condensation and a lamp with a water leak. Condensation appears in a lamp as very small droplets of water, a fine mist, or a white fog on the inside of the lens. It occurs when the air inside the lens reaches the “dew point.” This is the temperature at which the humidity in the air is cooled enough to become liquid. The most prevalent time of the year for fogging to occur is in the spring and fall.


Most exterior lamps on GM vehicles are designed to expel accumulated vapor through a vent system. Although the vent system operates at all times, it is most effective when the lamp is on and the vehicle is moving.


The amount of time required for the lamp to clear may vary from two to six hours. Customers with short commutes will experience a longer time to clear the lamp.


If these conditions are noted, advise the customer that replacing a lamp assembly may not correct this condition.


Typically, the condensation is located primarily in the lens corners (near the vents) and does not cover more than half of the lens surface. (Fig. 5) The condition should clear of moisture when the vehicle is parked in a dry environment, or when the vehicle is driven with the lights on.


F05 lamp fogging

Fig 5


Water Leak


A water leak is evidenced by numerous drops of water in various sizes, collecting on the inside surface of the lamp lens after the vehicle has been exposed to rain or a car wash. (Fig. 6)


A water leak condition will cover more than half the surface of the lamp lens. In addition, there may be an accumulation of water in the bottom of the lamp assembly. This condition will not clear when the vehicle is parked in a dry environment, or when the vehicle is driven with the lights on.


F06 lamp leak

Fig 6


Lamp Service Tips


When diagnosing or repairing a lamp for condensation or a leak:

• Do not replace lamps for fogging.

• Do not modify the lamp housing, such as drilling holes.

• Do not use the incorrect bulbs for the application, which may damage the housing and connector.

• Cold water in a car wash on a hot day may cause headlamp fogging.

• Use care when removing and installing lenses to prevent damage to the housing and mounting tabs.


For example, on the 2014-2015 Silverado 1500 and Sierra 1500 trucks, when removing and installing the tail lamps, do not apply excessive pressure to the lamp lens using your thumbs. Use your palms to pull or push the lamp. Applying too much pressure on the lens can cause the housing to crack behind the reflector field of the lamp.


When servicing any exterior lighting assembly, be sure to transfer electrical connection seals to the new part. They are often on the body side of the harness connection, but may have stayed on the part being replaced. If not transferred to the new part, the connection may corrode due to water entry.


Use of Non-GM Lamps


Many aftermarket companies manufacture lamp assemblies that look very similar to the original equipment (OE). Non-OE lamps may be installed on vehicles as part of a collision repair.


If these lamps are holding moisture or the bulbs are inoperative due to corroded electrical connections, they are not covered by the New Vehicle Warranty. Check for the GM trademark on the part label. (Fig. 7) Not all lamp assemblies currently have the trademark, but future assemblies will contain the trademark on the label.


Parts without the GM trademark are not eligible for replacement under warranty.


F07 lamp trademark

Fig 7


– Thanks to Gary McCraw



Rechargeable Energy Storage System Smoke Testing

Any time internal battery service is performed on the 2011-2014 Volt and 2014 ELR, a smoke test should be performed on the rechargeable energy storage system following the appropriate Service Information procedures.


A smoke test is critical to ensuring the integrity and proper operation of the high voltage battery pack and housing. For example, if the weather pack connections (housing) are damaged (Fig. 8), a smoke test will identify any broken electrical connections. A damaged connector, as shown, could impact the weatherpack seal and allow moisture inside the battery pack.


F08 BDUConnect1

Fig 8


TIP: Always perform the High Voltage Disabling procedure prior to servicing any high voltage component or connection. Personal Protection Equipment (PPE) and proper procedures must be followed.


The test requires Battery Smoke Test Leak Adapters (EL-50812) and the Evaporative Emissions System Tester (GE 41413-A). The Battery Smoke Test Leak Adapters should be installed to all of the Rechargeable Energy Storage System electrical connectors. The Evaporative Emissions System Tester hose is installed to the battery Rechargeable Energy Storage System adapter to inject smoke into the battery. (Fig. 9)


TIP: Only nitrogen is approved to generate smoke for EV battery leak testing. Compressed air should not be used. The GE-41413-A tester uses nitrogen and the fittings are designed to not allow it to be connected to compressed air in the shop.


F09 smoke tester to battery R

Fig 9


Once the Rechargeable Energy Storage System is filled with smoke, use a high-intensity white light to look for any visible smoke emitting from the system. Repair any visible leaks by retightening the fasteners or resealing any areas using butyl sealant. Refer to the Rechargeable Energy Storage System Smoke Test in the appropriate Service Information for complete repair information.


In addition, always follow the procedures for properly removing the cables from the Drive Motor Battery, including the Body Harness Connector (Fig. 10, A) and Interlock Loop Connectors. (Fig. 10, B) Wrap the exposed electrical connections with electrical tape to keep coolant out of the connections.

F10 drive motor battery connections R

Fig 10


– Thanks to Keith Newbury

A/C Tube Repair Kits for Auxiliary A/C and Heater Pipes

New A/C Tube Repair Kits are now available as an alternative repair technique to using a J-41425 A/C Line Repair Kit to repair auxiliary air conditioning and heater pipes. The kits can be used when there is rub-through damage, collision damage or leaking in the A/C or heater lines.


Starting with the 2015 model year full-size SUVs, vehicle specific repair kits (Fig. 11) will exist in the Electronic Parts Catalog (EPC). Detailed repair instructions are available for 2015 model year full-size SUVs in the appropriate Service Information (Reference Document ID # 3535636 in HVAC Repair sections).


F11 ac tube kit

Fig 11


The A/C Tube Repair Kits require a specific length of tube/pipe be removed to accommodate the length added by the coupler body. The length removed at the service cut location varies for each kit size. Only use the A/C Tube Repair Kits on straight sections that are long enough to accommodate the coupler length.

Screen Shot 2014-04-22 at 3.05.48 PM

– Thanks to Chris Semanisin, Frank Rogers, and Larry Kasperek

Brake Noise during Slow Stops

When applying the brakes on the 2014 Camaro Z/28 during a slow stop, a growl noise may be heard coming from the front or rear brakes.


Some noise is normal with all braking systems and differences in loading, type of driving, or driving style can make a difference in brake wear on the same make and model vehicle. Depending on weather conditions, driving patterns, and the local environment, brake noise may become more or less apparent. First, verify that all metal-to-metal contact areas between pads, pad guides, calipers, and knuckles are clean. Brake noise also may be caused by a “slip-stick” vibration of brake components.


With the Camaro Z/28’s high performance braking system (Fig. 12), it may exhibit more noise at slower speeds than a conventional braking system. This is considered a normal characteristic of the vehicle and, typically, no repairs are needed for these types of noises.


2014 Chevrolet Camaro Z/28

Fig 12


If the noise condition can be duplicated after the initial inspection, and the cause cannot be attributed to the previously mentioned items, burnish the brakes on the vehicle and evaluate the condition.


Follow the brake burnishing procedure listed in the Owner’s Manual, beginning on page 9-8. The procedure for the Camaro Z/28 is different than the procedure for the Camaro ZL1 and the Camaro SS equipped with the 1LE “Track Package”.


TIP: The Camaro Z/28 uses Brembo® Carbon Ceramic-Matrix™ rotors, which is part of an entirely different type of braking system than the other Camaro models. If the incorrect procedure is followed, damage to the braking system/vehicle may result.


The brake burnishing procedure for the Camaro Z/28 model is a two-part procedure. The first part is intended for street driving only. If the customer will only be driving the vehicle on regular city streets, this procedure is all that is required. If the customer plans on preparing the vehicle for driving on a track, the Street Brake Burnishing procedure should be completed first, followed immediately by the Racing/Track Brake Burnishing procedure.


– Thanks to Matt Bierlein


Corvette Driver Mode Control

The different driver modes on the 2014 Corvette provide enhanced performance for different driving conditions by changing the throttle progression, shift mode, steering assist, limited slip differential, ride control, traction control, exhaust sound and other calibrations. There are five driver modes that can be selected using the Driver Mode Control located on the center console (Fig. 13): Weather, Eco, Tour, Sport, and Track.


F13 Driver mode control W

Fig 13


If the vehicle was in Weather or Track mode during the previous drive cycle, it will default to the Tour mode the next time the vehicle is turned on. This is design intent. No repairs should be performed.


It is important to understand that the display themes on the instrument cluster and drive modes are two separate items that can be linked together or selected separately. When linked, the instrument cluster display theme is configured for the selected drive mode — Weather, Eco, Tour modes: Tour theme; Sport mode: Sport theme; and Track mode: Track theme.


If a specific display theme for all drive modes is desired, or to have the display theme change each time a drive mode is changed, use the DIC Settings menu to select Link to Drive Mode – Track, Sport, or Tour for the cluster theme. (Fig. 14)


Regardless of the Display Theme setting, the drive mode will always default to Tour if the vehicle is turned off in the Weather or Track mode.


F14 DIC Display Theme

Fig 14


– Thanks to Jeremy Richardson

CTS Hazard Flashers Switch Operation Update

A BCM calibration has changed the operation of the hazard flashers switch on 2014 CTS sedan models produced after October 11, 2013, or any vehicle that has the BCM programmed during service. After the calibration update, the hazard flashers switch (Fig. 15) must be pressed and held for one second before the hazard flashers will operate.


F15 Flasher button

Fig 15


The hazard flashers also need a one second “all clear” status to change states. This means to turn off the hazard flashers, you must to remove your finger from the hazard switch for at least one second and then press the switch again for one second. If you do not remove your finger for at least one second, the system determines that the switch is still being pressed.


It is important to understand this normal operation and communicate it to customers to avoid misdiagnosis and unnecessary switch replacement. Refer to #PIC5935A and provide a copy to the customer.


– Thanks to Jean Hart and Stephen Jacob

New 2015 Silverado HD and Sierra HD Trucks

2015 Chevrolet Silverado LT 2500HD with Z71

Fig 1

2015 GMC Sierra Denali 2500HD

Fig 2


The new 2015 Silverado 2500HD-3500HD and Sierra 2500HD-3500HD pickup trucks recently made their debut. These new trucks feature all-new exterior designs along with many of the same enhancements found on the new 2014 Silverado 1500LD and Sierra 1500LD trucks. Plus, the trucks feature the latest generation Chevrolet MyLink™ and GMC IntelliLink™ infotainment systems.


The HD trucks are equipped with carryover chassis systems and powertrains from the previous generation HD trucks that are proven, powerful and extremely reliable. The HD trucks feature a choice of gasoline, bi-fuel and diesel engines.


Gasoline – 6.0L V8 (RPO L96)


The 6.0L V8 engine in the Silverado HD and Sierra HD produces 360 hp and 380 lb-ft of torque. In Silverado HD and Sierra HD models greater than 10,000 lbs. (cab chassis models only), the engine generates 322 hp and 380 lb-ft of torque. In Canada, these engines are rated at 335 hp.


Bi-Fuel Gasoline/CNG – 6.0L V8 (RPO LC8)


When using gasoline, the bi-fuel 6.0L V8 in the Silverado HD and Sierra HD produces 360 hp and 380 lb-ft of torque. When using CNG, the engine has 301 hp and 333 lb-ft of torque.


Diesel – 6.6L V8 (RPO LML)


The 6.6L Duramax diesel V8 engine in the Silverado HD and Sierra HD generates 397 hp and 765 lb-ft of torque.


Use only Ultra Low Sulfur Diesel Fuel or biodiesel blends up to 20% (B20). Avoid the use of biodiesel blends above 20%, which may damage the engine and fuel system.


The Diesel Exhaust Fluid (DEF) tank should be filled just prior to delivery using GM-approved DEF fluid, or fluid containing the API certified or ISO 22241 label.


The Duramax diesel features an elevated cold engine idle that can be turned on or off. To turn this feature on or off:

1. Turn the ignition to ON/RUN, with the vehicle off.

2. Press the accelerator pedal to the floor and hold while quickly pressing the brake pedal three times in less than eight seconds.

3. Release the accelerator pedal and start the engine.


The 2015 HD trucks offer two automatic transmissions: the Hydra-Matic™ 6L90 6-speed automatic transmission (RPO MYD) or the Allison 1000 6-speed automatic transmission (RPO MW7).


On 3500HD Cab Chassis models, the Allison 1000 6-speed automatic has an available Power Take Off (PTO). Under normal operating conditions, the PTO light on the instrument cluster will remain on throughout the PTO operating cycle. The PTO light will turn on and then turn off after one second If all conditions required to engage PTO have not been met when enabling PTO.

Brake System


A new brake fluid is required on the 2015 HD trucks. It has enhanced corrosion inhibitors and significant improvements in lubricity to help eliminate master cylinder squeak/noise. In the United States, use brake fluid GM P/N 19299818 and, in Canada, use brake fluid GM P/N 19299819. Do not use any brake fluid.


New to the dual rear wheel trucks and the cab chassis is a TRW EBC460 4-wheel disc brake antilock brake system. The electronic brake control module and the brake pressure modulator are serviced separately.


A number of vehicle performance enhancement systems also are available that aid in control of the vehicle in a variety of driving conditions.

Hill Descent Control


Hill Descent Control (HDC) sets and maintains vehicle speed while descending a very steep incline in a forward or reverse gear. Press the HDC switch on the center of the instrument panel to enable or disable HDC. (Fig. 3) Vehicle speed must be less than 31 mph (50 km/h). The HDC light displays on the instrument cluster when enabled.


2015 Chevrolet Silverado HD

Fig 3


HDC can maintain vehicle speeds between 2 and 14 mph (3 and 22 km/h) on an incline greater than or equal to a 10% grade. A blinking HDC light indicates the system is actively applying the brakes to maintain vehicle speed.


When HDC is activated, the initial HDC speed is set to the current driving speed. It can be increased or decreased by applying the accelerator or brake pedal. This adjusted speed becomes the new set speed. HDC will remain enabled between 14 and 37 mph (22 and 60 km/h); however, vehicle speed cannot be set or maintained in this range. It will automatically disable if the vehicle speed is equal to or greater than 50 mph (80 km/h), or more than 60 km/h (37 mph) for at least 30 seconds. Press the HDC switch again to re-enable HDC.


Integrated Trailer Brake Control


New for 2015 HD trucks, the Integrated Trailer Brake Control is now compatible with electric over hydraulic trailer brakes. The Integrated Trailer Brake Control system can be used to adjust the amount of power output, or Trailer Gain, available to the trailer brakes. The control panel also allows manual application of the trailer brakes.


Trailer Sway Control


Trailer Sway Control will detect any vehicle yaw (rotation) instability, caused by unintended side-to-side motion of a trailer while being towed. If sway is detected, the vehicle brakes are selectively applied at each wheel to help reduce excessive trailer sway. The engine torque also may be reduced to slow down the vehicle.


5th Wheel Wire Harness


The optional 5thh wheel wire harness (RPO UY2) is in a different location on the 2015 HD trucks. The harness is now located on the rear cross member just forward of the rear bumper in the center of the truck (Fig. 4), not on the front left box mount as it was on the previous truck model.


F04 truck harness

Fig 4


Duramax Diesel Engine Exhaust Brake

The diesel engine exhaust brake enhances the vehicle brake system and reduces brake lining wear by using engine braking created by the variable vanes in the turbocharger to generate additional backpressure in the engine.


The exhaust brake switch on the center of the instrument panel activates the system. (Fig. 5) The switch must be pressed at each vehicle start for the system to be active.


2015 Chevrolet Silverado HD

Fig 5



The 2015 HD trucks use GM’s Global A electrical architecture. This architecture requires the use of the Global Diagnostic System 2 (GDS 2) software and the Multiple Diagnostic Interface (MDI) module.


TIP: Do not swap modules in an attempt to diagnose a vehicle condition.


When certain modules are programmed and configured during installation, the module learns a specific environment identifier that is unique to the vehicle. With an incorrect identifier, vehicle starting is disabled.


Rear Vision Camera and Park Assist

The 2015 HD trucks features a Rear Vision Camera and Front and Rear Park Assist, which provide a view directly behind the vehicle when in Reverse as well as distance-to-closest-object information.


TIP: The RVC and Rear Park Assist (RPA) will not work properly if the tailgate is down. If the tailgate is down, do not use these systems.


The Rear Vision Camera must be disconnected if the tailgate needs to be removed by disconnecting the connector from the electrical junction block on the left side of the cross member of the vehicle frame. After disconnecting, use the cap mounted next to the camera connector to cover the open terminals on the junction block.

TIP: Do not install any brush guards, grill guards, winches etc., on vehicles equipped with front park assist.

Rear park assist can be turned OFF, ON or ON with Towbar through the Vehicle Settings menu. The ON with Towbar setting allows for the park assist system to work properly with a small item attached to the trailer hitch. Turn the rear park assist system off when towing a trailer or using a large drawbar.


Transport Mode

The HD trucks are shipped in Transport Mode to save battery power. To turn the Transport Mode off, start the vehicle, activate the hazard flashers, press the brake pedal, and then turn the ignition key to the crank position for 15 seconds. The same steps are used to turn on the feature.


– Thanks to B.J. Lackey and Sherman Dixon



The 2015 2500HD Trucks’ CNG System

2015 Silverado 2500HD Bi-Fuel

Fig 6


The new 2015 Silverado 2500HD and Sierra 2500HD pickup trucks feature bi-fuel gasoline/CNG operation.  The operation of the bi-fuel gasoline/CNG 6.0L V8 engine (RPO LC8) is very similar to past model years. For 2015, there are new switches and Driver Information Center (DIC) messages.


The 6.0L V8 engine is equipped with special hardened valves and valve seats to enable operation on gasoline or compressed natural gas (CNG).


CNG Indicator Lamp


The CNG fuel selector switch indicator on the center of the instrument panel (Fig. 7) shows the current fuel mode, indicates a transition between fuels and if there is a system error.


Off: Vehicle is currently operating on gasoline.

On: Vehicle is currently operating on CNG.

Flashing Slowly (Once per Second): Vehicle is awaiting changeover to selected fuel or has started the changeover.

Flashing Rapidly (10 Times per Second): CNG system error. The light will continue to flash rapidly until the problem is corrected.


2015 Silverado 2500HD Bi-Fuel

Fig 7


CNG Fuel Selector Switch


Regardless of which fuel mode is selected, gasoline or CNG, the vehicle always starts on gasoline. When the ignition is in ON/RUN, press the CNG fuel selector switch to select gasoline or CNG.


When CNG mode is selected, the vehicle will automatically transition from gasoline to CNG when conditions for CNG operation have been met. While waiting to transition, the fuel selector switch indicator will flash. At temperatures colder than 32°F (0°C), it may take 10 to 15 minutes for the vehicle to switch from gasoline to CNG.


If operating in CNG mode and the CNG tank is emptied, the vehicle will automatically switch to gasoline operation and the switch indicator will flash continuously. Press the CNG fuel selector switch to stop the indicator flashing. Always keep the gasoline tank adequately filled. The system will not switch over to CNG operation if the vehicle runs out of gasoline.


TIP: If the vehicle is heavily loaded, such as when towing a trailer up a grade, it may be prevented from switching to CNG. Once the high loads are no longer present, the system will switch.


Fuel Gauge Operation


The vehicle has a gasoline/CNG fuel gauge. When the ignition is ON, the gasoline/CNG fuel gauge indicates approximately how much fuel is left in the tank. When the engine is running, the fuel gauge displays the level for the type of fuel that is currently being used. The fuel level for the second fuel that is not being used (gasoline or CNG) is displayed in the DIC. (Fig. 8)


2015 Silverado 2500HD Bi-Fuel

Fig 8


CNG Fuel Tank

There are two methods of refueling: fast filling or slow filling. Fast filling is normally used in fuel stations for natural gas vehicles. It takes about six to eight minutes to fill up the fuel tank. Slow filling is done with a vehicle refueling appliance or a time-fill post provided by the fleet operator. Refueling time varies depending upon the refueling system used.


Turn off the engine prior to refilling. Remove the dust cap from the fuel fill valve/receptacle (Fig. 9), clean off any dirt or debris on the fuel fill valve/receptacle, and follow the refueling instructions on the pump or provided by the station operator. Refueling will stop automatically when the tank is full. Wait for the high pressure fuel to be purged from the hose before disconnecting.


To disconnect the vehicle from the refueling station, remove the nozzle from the fuel fill valve/receptacle. A hissing sound may be heard as a small amount of natural gas escapes. This is normal. Put the fill valve dust cap on securely and close the fuel fill door.


2015 Silverado 2500HD Bi-Fuel

Fig 9


– Thanks to B.J. Lackey, Sherman Dixon and Chris Graham


New Engine Technologies and New Sounds

The latest generation of engine technologies found on the 2014 Corvette and 2014-2015 Silverado 1500, Suburban, Tahoe, Sierra 1500, Yukon and Yukon XL may produce some unfamiliar sounds during cold starts as well as during warm operation. The new engines include the 4.3L V6 (RPO LV3) (Fig. 10), 5.3L V8 (RPO L83), 6.2L V8 (RPOs L86 and LT1).


F10 4.3L V6

Fig 10


Direct Injection


The new small block engine family uses a Direct Injection (DI) fuel system. The fuel is injected directly into the cylinder using a high pressure fuel system, which improves power, torque, and fuel efficiency. The high pressure fuel pump can generate a subtle ticking sound that is apparent when the vehicle is idling. The sound is more evident when outside the vehicle, when the hood is open or the vehicle is operated in a drive-through environment. The sound may be more noticeable during a cold start, but lessens once the engine is warm. A slightly higher pitched clicking sound is the fuel injectors pulsing on and off under the high fuel pressures. These sounds are normal characteristics of the DI system.


Another operating characteristic is a slightly longer crank time, which is the result of the time required to build high pressure in the fuel system before the engine starts.


Oil Pump


The oil pump design on these engines is a two-speed vane-type pump. Its dual-pressure control enables operation at a very efficient oil pressure at lower rpm, and then delivers higher pressure at higher engine speeds.


At temperatures of 32°F (0°C) or colder, when the engine has been sitting for a few hours, it is possible to have air enter the pump through normal oil drainback. Upon start-up, a short rasp sound may be heard from the front of the engine. It is most often heard during a remote start. This is a normal condition.


– Thanks to Ian Doran

eAssist Battery Module and Battery Exchange Process Update

The Drive Motor Generator Battery Module (Powerpack) and Drive Motor Generator Battery exchange process for the 2012-2014 LaCrosse and Regal, 2013-2014 Malibu Eco, and 2014 Impala with eAssist has been updated.


The exchange program is designed to gain important feedback on the Drive Motor Generator Control and Battery Module Assembly or Battery sections regarding service diagnostics, repair procedures, and accelerated root cause analysis for continuous improvements.


Please review all of the information provided in #PIC5520K prior to contacting the Technical Assistance Center (TAC). This information covers parts information, storage guidelines, shipping preparations, and shipping instructions.


TIP: Do not attempt to reprogram software or clear any DTCs prior to capturing data and calling TAC.


Always perform the High Voltage Disabling procedure prior to servicing any high voltage component or connection. Personal Protection Equipment (PPE) and proper procedures must be followed.


It will be necessary to have the 16-digit Battery Identification Number (BIN), located on the side of the battery module assembly cover. (Fig 11)


F11 2688041 Battery Pack label

Fig 11


After obtaining a case number and authorization through TAC, the TAC Consultant will call the dealership’s local Electronic Service Center (ESC) to order the Drive Motor Generator Battery Module or Drive Motor Generator Battery Sections 1 and 2.


– Thanks to Brian Ciaverella

HVAC Temperature Fluctuations

On some 2014 Corvettes built prior to November 15, 2013 the HVAC temperature may fluctuate more than expected when the set temperature is changed by only a few degrees or less. A minor change in the set temperature may cause the HVAC system to blow warmer or cooler than desired.


Do not replace parts for this condition. A revised HVAC control module calibration has been released to provide an improvement to this condition.


• Determine the build date of the vehicle in order to confirm which module(s) require an update.

–   If the build date is November 5, 2013 or later, update the HVAC control module.

–   If the build date is prior to November 5, 2013, determine if the latest version of #PI1101 (labor operation code 2880178) has been performed.

–   If the latest version of #PI1101 has been performed, update only the HVAC control module.

–   If the latest version of #PI1101 has not been performed, perform the procedure as instructed. Submit a warranty transaction for #PI1101 only.


• The revised HVAC control module calibration will improve the condition noticeably, but if there are still concerns after the calibration has been updated, there are settings that can be made to further improve the operation. In the Vehicle Settings menu, set the Auto Fan Max Speed to Low or Medium instead of High. Go to Vehicle > Climate and Air Quality > Auto Fan Max Speed. (Fig. 12) By selecting a reduced blower speed, the system will have smoother temperature changes as it attempts to adjust the temperature in the car.


F13 Corvette Vehicle Clmate Fig 12


• It is vital to the operation of the system that all programming events be completed as instructed in the appropriate module Programming and Setup documents. System operation will not improve if procedures are not completed as instructed in the Service Information.


– Thanks to Jeremy Richardson

Removing Rear Park Assist

If a customer or upfitter removes the rear bumper, installs a different rear bumper, or adds a different box/flat bed/cube box/hitch, etc. to a 2007-2013 Silverado or Sierra, or a 2014 Silverado 2500/3500 or Sierra 2500/3500 model equipped with Rear Park Assist (RPO UD7), it will affect Rear Park Assist operation.


In these cases, the Rear Park Assist feature can be removed from the vehicle. Follow these instructions for the applicable model year:


1. On all model years, disable the Rear Park Assist Module (in most cases, by removing the OBS DET fuse 20, 10 amp, from the left I/P fuse block).

2. For 2007-2009 models, contact the Techline Customer Support Center to obtain an Instrument Panel Cluster (IPC) calibration to disable the option.

3. For 2010-2014 models, remove power to the IPC for several minutes by disconnecting the battery. When power is reconnected, the IPC will not see the Park Assist Module on the low speed data buss (because it was disabled in Step 1) and reconfigure the IPC without Rear Park Assist. After this is complete, there will be not any Rear Park Assist warning messages displayed.



Since the affected vehicle was modified outside of production specifications, these procedures should not be charged under warranty.


– Thanks to Scott Fibranz

Stop Lamp and Turn Signal Lamp Options

For some 2009-2014 Express and Savana Cutaway Vans, there may be some confusion regarding the proper operation of the stop and/or turn signals. This may lead to difficultly diagnosing a stop and/or turn signal condition.


The BCM can be calibrated for Separated Stop/Turn Signal Circuits, RPO V4D.


Without RPO V4D


The stop and turn signals are one lamp (same bulb). Traditionally, there will be one red stop/turn signal lamp per side.


Without RPO V4D: Circuit 618 Yellow (X405 terminal D) is for the left stop and turn signal. Circuit 619 Dk Green (X405 terminal E) is for the right stop and turn signal.


With RPO V4D


The stop and turn signals are separate lamps (two different bulbs). Traditionally, there will be one red stop lamp and one amber turn signal lamp per side. RPO V4D is included with the Ambulance Package (RPO YF2), School Bus Package (RPO B3D) and Shuttle Bus Package (RPO ANC).


With RPO V4D: Circuit 618 Yellow (X405 terminal D) is for the left turn signal only. Circuit 619 Dk Green (X405 terminal E) is for the right turn signal only. Circuit 1320 light blue (X405 terminal C) is for the stop lamps only.


If the vehicle is upfitted and the body does not support the way the BCM is calibrated for the stop/turn signal setup, contact the Techline Customer Support Center for a new BCM calibration to either remove or add the RPO V4D option.


– Thanks to Scott Fibranz


Favorites List Infotainment Display

2015 Suburban, Tahoe, Yukon, Yukon XL; 2014-2015 LaCrosse, CTS coupe, ELR, Corvette, Impala, Silverado 1500, Sierra 1500; and 2013-2015 ATS, SRX, and XTS models with Infotainment Systems RPO IO5 or RPO IO6 will have part of the infotainment display covered when the radio station favorites list is maximized. (Fig. 13) This will prevent the selection of certain functions.


F12 3781718 Fig 13


This is a normal operating characteristic and no repairs should be made. The hidden screen functions can be accessed again after the user minimizes the favorites list. The favorites list can be minimized by dragging it to the bottom of the display.


– Thanks to Steven Morris

Service Know-How

10214.04D – Emerging Issues

April 10, 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


Screen Shot 2014-04-08 at 10.43.18 AMScreen Shot 2014-04-08 at 10.43.03 AM

Truck Issues – Fix It Right the First Time


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