Archive for May 2012

Under Body Noise on Uneven Road Surface

2008-2012 Malibu models may experience a noise heard from under the front of the body or suspension area. The pop, snap, creak or clunk noise may be present on braking, turning or driving on an uneven road surface.

The noise may be caused by the front cradle body mount bolt washers or cradle making contact with the frame rail.

Inspect the washer-to-cradle clearance and the cradle-to-frame rail flange clearance. Inspect for any witness marks. (Fig. 4, 5)

FIGS 4, 5

 

The body bolt mount washers and rail flange should have 5 mm clearance. (Fig. 6) Loosen all cradle mount bolts, center the cradles as needed, and torque to specification. Then perform a 4-wheel alignment.

FIG 6

 

- Thanks to David Roat

 

New 8-Pin Mass Air Flow, Humidity, BARO and Intake Air Temperature 1 and 2 Sensor

Beginning with the 2012 model year, a new 8-pin Mass Air Flow (MAF), Humidity, Barometer (BARO) and Intake Air Temperature (IAT) 1 & 2 sensor is being used on some gasoline engines.

There are two suppliers of the 8-pin sensor, Bosch and Hitachi. The Hitachi sensor is used on most of the applications at this time. The sensors are also known as the Multifunction Intake Air sensor or mini-weather station sensor.

The new sensor measures the intake air’s humidity. A second air temperature sensor is housed in the assembly to accurately measure the air temperature at or very near the humidity sensor. The ECM uses the air temperature to calculate the air humidity, which is displayed by the scan tool as Intake Air Humidity (%). The signal is transmitted on the circuit as duty cycle (%). The intake air temperature sensor 2 is transmitted to the ECM as a frequency (Hz), on the same circuit as the humidity signal. The scan tool displays the IAT sensor 2 in degrees (°C /°F) and frequency (Hz).

Harness and internal sensor differences do not permit interchangeability between the Hitachi and Bosch sensors. However, both have the following functions:

  • MAF sensor
  • IAT sensor 1
  • BARO sensor (Throttle Inlet Air Pressure – TIAP)
  • Humidity sensor
  • IAT sensor 2 (Humidity Air Temperature)

The Hitachi sensor terminals are connected to the vehicle and the ECM as follows:

  • Pin 1 – Signal, IAT 1
  • Pin 2 – +5V Reference
  • Pin 3 – Low Reference
  • Pin 4 – Signal, BARO (TIAP)
  • Pin 5 – Ignition, +12V
  • Pin 6 – Signal, MAF
  • Pin 7 – Ground, Chassis
  • Pin 8 – Signal, Humidity (duty cycle – %) and IAT 2 (frequency – Hz)

The Bosch sensor terminals are connected to the vehicle and the ECM as follows:

  • Pin 1 – Signal, Humidity (duty cycle – %) and IAT 2 (frequency – Hz)
  • Pin 2 – +5V Reference
  • Pin 3 – Signal, MAF
  • Pin 4 – Ground, Chassis
  • Pin 5 – Ignition, +12V
  • Pin 6 – Signal, BARO (TIAP)
  • Pin 7 – Low Reference
  • Pin 8 – Signal, IAT 1

The gasoline engines replace the Mass Air Flow/Intake Air Temperature (MAF/IAT) 5-pin sensor with the 8-pin Multifunction Intake Air sensor.

The 6.6L Duramax diesel engines (RPOs LML, LGH) will use the new Hitachi 8-pin sensor for the first time in the 2013 model year. (Fig. 7, B) For diesels, the Multifunction Intake Air sensor is used with the existing MAF/IAT 5-pin sensor. (Fig. 7, A)

FIG 7

The new sensor is in the diesel’s air stream, ahead of the existing MAF/IAT, requiring a shift of some intake air sensor names:

  • New IAT sensor (integrated with the Humidity sensor) is IAT 1
  • Old IAT sensor 1 (integrated with the MAF sensor) becomes IAT 2
  • Old IAT 2 (located before the inlet to the Charge Air Cooler) becomes IAT 3

The diesel engines use three of the eight pins of the Hitachi sensor:

  • Pin 5 – Ignition voltage
  • Pin 7 – Ground
  • Pin 8 – Signal, Humidity (duty cycle – %) and IAT 1 (frequency – Hz)

The diesel engines use two of the sensor’s functions:

  • - Humidity sensor
  • - IAT sensor 1 (Humidity Air Temperature)

TIP: The diesels use different/new DTCs for similar sensors used on gasoline engines.

2012 and 2013 Gas Engine-related DTCs for Multifunction Intake Air Sensors

  • DTC P0096: Intake Air Temperature (IAT) Sensor 2 Performance
  • DTC P0097: Intake Air Temperature (IAT) Sensor 2 Circuit Low Voltage
  • DTC P0098: Intake Air Temperature (IAT) Sensor 2 Circuit High Voltage
  • DTC P0099: Intake Air Temperature (IAT) Sensor 2 Circuit Intermittent
  • DTC P0101: Mass Air Flow (MAF) Sensor Performance
  • DTC P0102: Mass Air Flow (MAF) Sensor Circuit Low Frequency
  • DTC P0103: Mass Air Flow (MAF) Sensor Circuit High Frequency
  • DTC P0111: Intake Air Temperature (IAT) Sensor 1 Performance
  • DTC P0112: Intake Air Temperature (IAT) Sensor 1 Circuit Low Voltage
  • DTC P0113: Intake Air Temperature (IAT) Sensor 1 Circuit High Voltage
  • DTC P0114: Intake Air Temperature (IAT) Sensor 1 Circuit Intermittent
  • DTC P112B: Intake Air Temperature (IAT) Sensor 3 Performance (Turbocharged applications)
  • DTC P112C: Intake Air Temperature (IAT) Sensor 3 Circuit Low Voltage (Turbocharged applications)
  • DTC P112D: Intake Air Temperature (IAT) Sensor 3 Circuit High Voltage (Turbocharged applications)
  • DTC P112E: Intake Air Temperature (IAT) Sensor 3 Circuit Intermittent (Turbocharged applications)
  • DTC P11C2: Intake Air Humidity Sensor Circuit Low Voltage
  • DTC P11C3: Intake Air Humidity Sensor Circuit High Voltage
  • DTC P11C4: Intake Air Humidity Sensor Circuit Erratic
  • DTC P2199: Intake Air Temperature (IAT) Sensor 1-2 Correlation
  • DTC P2227: Barometric Pressure (BARO) Sensor Performance
  • DTC P2228: Barometric Pressure (BARO) Sensor Circuit Low Voltage
  • DTC P2229: Barometric Pressure (BARO) Sensor Circuit High Voltage
  • DTC P2230: Barometric Pressure (BARO) Sensor Circuit Erratic

2013 Duramax Diesel Engine-related DTCs for Multifunction Intake Air Sensors

  • DTC P00EA: Intake Air Temperature (IAT) Sensor 3 Circuit Low Voltage – new DTC
  • DTC P00EB: Intake Air Temperature (IAT) Sensor 3 Circuit High Voltage – new DTC
  • DTC P00F4: Intake Air Humidity Sensor Circuit Low Voltage – new DTC
  • DTC P00F5: Intake Air Humidity Sensor Circuit High Voltage – new DTC
  • DTC P00F6: Intake Air Humidity Sensor Circuit Erratic – new DTC
  • DTC P0096: Intake Air Temperature (IAT) Sensor 2 Performance
  • DTC P0097: Intake Air Temperature (IAT) Sensor 2 Circuit Low Voltage
  • DTC P0098: Intake Air Temperature (IAT) Sensor 2 Circuit High Voltage
  • DTC P0099: Intake Air Temperature (IAT) Sensor 2 Circuit Intermittent
  • DTC P0101: Mass Air Flow (MAF) Sensor Performance
  • DTC P0102: Mass Air Flow (MAF) Sensor Circuit Low Frequency
  • DTC P0103: Mass Air Flow (MAF) Sensor Circuit High Frequency
  • DTC P0111: Intake Air Temperature (IAT) Sensor 1 Performance
  • DTC P0112: Intake Air Temperature (IAT) Sensor 1 Circuit Low Voltage
  • DTC P0113: Intake Air Temperature (IAT) Sensor 1 Circuit High Voltage
  • DTC P0114: Intake Air Temperature (IAT) Sensor 1 Circuit Intermittent
  • DTC P2199: Intake Air Temperature (IAT) Sensor 1-2 Correlation
  • DTC P2227: Barometric Pressure (BARO) Sensor Performance
  • DTC P2228: Barometric Pressure (BARO) Sensor Circuit Low Voltage
  • DTC P2229: Barometric Pressure (BARO) Sensor Circuit High Voltage
  • DTC P2230: Barometric Pressure (BARO) Sensor Circuit Erratic

- Thanks to W. Michael Schallmo

Leak Diagnosis Using Leak Trace Powder

Continued refinement of engineering, materials, and manufacturing processes has greatly reduced the occurrence of fluid leaks (engine oil, transmission fluid, coolant, power steering fluid, and brake fluid). Although rare, fluid leaks occasionally occur, so locating the source of fluid leaks remains an important skill for technicians to master.

There is some important information about leak diagnosis in the Service Information. In addition, leak diagnosis was discussed in the April 2012 Emerging Issues seminar (In Canada, June 2012 TAC Talk).

One of the methods mentioned requires the use of leak trace powder. Here are some highlights.

Because the customer has probably driven the vehicle for awhile with the leak, the fluid will be splattered about and the source of the fluid leak will not be obvious. Attempt to identify the type of fluid from the color, smell and feel of the fluid. Then, thoroughly wipe the suspected leak area with a shop towel.

TIP: Do not use brake cleaner or other reactive solvents. These solvents can damage rubber gaskets, seals and bushings.

After cleaning the suspected leak area, spray aerosol-type leak tracing powder to cover the area.

Drive the vehicle for 15–20 minutes under city driving conditions until normal operating temperatures are reached. Do not drive at highway speeds because this will cause the leaking fluid to spread.

Trace the leak path through the powder back to the source of the leak and make the necessary repairs. (Fig. 8)

FIG 8

Additional Uses for Leak Trace Powder

Leak trace powder also can be used to determine if proper contact is being made between seals on weatherstrips around doors, trunks, hatches, and sunroofs.

Spray the powder on the frame where the seal should make contact and then gently close the panel. Open the panel and inspect the seal. The powder will transfer to the seal where contact is made. Gaps in the powder on the seal indicate a possible wind or water leak area.

- Thanks to Dave Peacy

Multi-Axis Acceleration Sensor Module Sets History DTC

When performing a DTC check using a scan tool on the 2013 Malibu, the Multi-Axis Acceleration Sensor Module may have a DTC U0121 (Loss of Communication with the EBCM) set in history. If the DTC is cleared, it may set again and immediately go to history during the next ignition cycle. No messages or warning lamps will display.

This is a characteristic of normal operation. Do not replace any parts or attempt to repair. At key-up, the Multi-Axis Acceleration Sensor Module is looking for a response from the Electronic Brake Control Module (EBCM) right away. Because it does not receive the response immediately, it sets DTC U0121 momentarily and then goes to history.

- Thanks to Christopher Crumb

Intermittent Service Power Steering Message with DTC U0131

On some 2011-2012 Lacrosse, 2012 Regal, and 2013 Malibu models with electric power steering (RPO NJ1), there may be an intermittent Service Power Steering message displayed on the Driver Information Center along with a set DTC U0131 (Lost Communication With Power Steering Control Module).

This condition may be caused by a loose B+ feed at the X50A Underhood Fuse Block or the 80A fuse retaining bolts in the Underhood Fuse Block. (Fig. 9) The battery feed is X6 on the LaCrosse and Malibu and X8 on the Regal. The condition also may be caused by a loose connection at G111.

Secure the B+ feed or fuse nuts as needed. In addition, check the connection at G111.

FIG 9

- Thanks to Christopher Crumb

Blower Motor Inoperative after Blower Control Module Replacement

After replacing the Blower Motor Control Module with part number 89019351 on some 2004-2007 Rainier; 2003-2006 Escalade models; 2003-2006 Avalanche, Suburban, Tahoe; 2003-2007 Silverado Classic, Trailblazer XL; 2003-2009 Trailblazer; 2003-2007 Envoy XL, Envoy XUV, Sierra Classic; 2003-2009 Envoy; 2003-2006 Yukon models; and 2003-2004 Bravada models equipped with automatic climate control, the blower motor may be inoperative. This condition may occur if the blower motor speed is set to any speed position, except for Low, when the key is turned off. Upon the next key on, the blower motor may be inoperative.

An updated blower motor control module has been released to address this condition. If this condition is present, replace the previously installed Blower Motor Control Module (part number 89019351) with the updated Blower Motor Control Module (part number 19260762).

- Thanks to Jim Will

Service Replacement Engines with Temporary Emission Exemption Tag

A service replacement engine used on 2013 and prior GM passenger cars and trucks may contain a Temporary Emission Exemption. (Fig. 10) This label is not a concern. It is attached to service replacement engines due to a new Federal Law/Mandate.

Follow the related engine installation instructions to install the engine.

FIG 10

- Thanks to James Parkhurst

Service Know-How

10212.05D – Emerging Issues

May 10, 2012

To view Emerging Issues seminars:

Log in to www.gmtraining.com, select Service Know-How/TECHAssist from the menu, select Emerging Issues, and then Searchable Streaming Video to choose the current Emerging Issues seminar or past programs.

Car Issues – Fix It Right the First Time

Truck Issues – Fix It Right the First Time