Symptom:
P0401 - EGR SYSTEM PERFORMANCE
When Monitored and Set Condition:
P0401 - EGR SYSTEM PERFORMANCE
When Monitored: Engine running for greater than two minutes with the Engine Coolant
Temp greater than 70°C (158°F). EGR active. Less than 8500 feet. Ambient temperature
greater than 20°F (-6°C)
Set Condition: 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 two different O2 Sensor signal
reading (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.
POSSIBLE CAUSES
GOOD TRIP EQUAL TO ZERO
EGR VALVE OPEN AT IDLE
EGR VALVE ASSEMBLY INSPECTION
EGR SOLENOID ASSEMBLY
EGR SOLENOID GROUND CIRCUIT OPEN
EGR SOLENOID CONTROL CKT SHORT TO GND
EGR SOLENOID CONTROL CKT SHORTED TO VOLTAGE
EGR SOLENOID CONTROL CKT OPEN
PCM - EGR OPEN
PCM - EGR CLOSED
TEST ACTION APPLICABILITY
1 Turn the ignition on.
With the DRBIIIt, read DTCs and record the related Freeze Frame data.
Is the Good Trip displayed and equal to zero?
All
Yes → Go To 2
No → Refer to the INTERMITTENT CONDITION symptom in the
Driveability category.
Perform POWERTRAIN VERIFICATION TEST VER-5-NGC.
143
DRIVEABILITY - NGC
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