For a complete wiring diagram Refer to Section 8W.
Exhaust gas recirculation is a method of reducing emissions of oxides of nitrogen. As the inert exhaust gas is recirculated, the mixture absorbs heat in the combustion chamber without interacting with the fuel/air mixture and reduces the formation of NOx emissions. After the EGR monitor conditions are met, the EGR valve is turned on and off momentarily. The EGR monitor calculated the difference in engine roughness from the EGR off condition to the EGR condition. This engine combustion stability difference as measured by engine roughness is the measure of a functional EGR system.
Engine running for greater than two minutes with the Engine Coolant Temp greater than 70 degrees C (158 degrees F). EGR active. Less than 8500 feet. Ambient temperature greater than -6 degrees C (20 degrees F).
The PCM closes the EGR valve while monitoring the O2 Sensor signal. Once a closed EGR fueling sample has been established the PCM then ramps in EGR and additional fueling while monitoring the O2 sensor signal in the open state. A fueling sample is again established. The PCM then compares the different O2 Sensor signal readings (fueling samples). If a larger than expected variation is detected, a soft failure is recorded. Three soft failures set a one trip failure. After two failed trips, a DTC is set and the MIL is illuminated.
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Possible Causes
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(Z906) EGR SOLENOID GROUND CIRCUIT OPEN |
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(K35) EGR SOLENOID CONTROL CIRCUIT SHORTED TO GROUND |
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(K35) EGR SOLENOID CONTROL CIRCUIT SHORTED TO BATTERY VOLTAGE |
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(K35) EGR SOLENOID CONTROL CIRCUIT OPEN |
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EGR SOLENOID ASSEMBLY |
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PCM |
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).
NOTE: It may be necessary to drive the vehicle to meet the conditions to set this DTC, try to repeat the conditions in which the fault originally set by reviewing the Freeze Frame data.
NOTE: If the vehicle is running rough at idle (scan tool not actuating) follow the yes path to continue.
CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool #8815 to perform diagnosis.
NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.