P0402

Possible Stuck EGR Valve Pintle With Or Without Service Engine Soon (SES) DTCs P0101 P0402 - keywords black box diesel DTC engine lamp light MIL mode power reduced smoke - (Mar 31, 2010)

Subject: Possible stuck open EGR valve pintle with or without Service Engine Soon [SES] DTC P0101 P0402

Models: 2004-2009 Chevrolet Express, Kodiak, Silverado
2004-2009 GMC Savana, Sierra, Topkick
Equipped with the 6.6L Duramax Diesel Engine RPO codes LLY , LBZ , LMM (VIN's 2 , D , 6 and 9)

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:

Some customers may comment on an illumination of the check engine light.

Upon further investigation, the technician may find the following DTCs stored in the ECM:

DTC P0101: Mass Air Flow (MAF) Sensor Performance

DTC P0402: Exhaust Gas Recirculation (EGR) Flow Excessive

Recommendation/Instructions:

Complete the current SI diagnostic for any codes setting.

If MAF readings are found to be lower than a like truck with the EGR commanded closed, the codes could be setting due to non-sealing, or partially stuck open EGR valve.

Note: The EGR Pos. sensor is in the EGR motor and is not directly connected to the EGR pintle therefore it is possible to see a 0% EGR Pos. sensor reading when the EGR pintle is stuck open and or not seating fully.

If the EGR valve is found stuck open on 2006 and 2007 LLY and LBZ refer to the latest version of bulletin # 06-06-04-066D to check for the latest ECM calibration, and to clean the EGR valve.

If the EGR valve is found stuck open on 2004 and 2005 LLY and 2007 to 2009 LMM , replace the EGR valve Using SI repair document for EGR valve replacement. Verify the latest ECM calibrations.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.