P0401

Schematic:

The Exhaust Gas Recirculation (EGR) valve consists of a pintle valve which moves by the use of an internal solenoid and an internal position sensor (potentiometer) used to determine pintle valve position. The PCM controls the solenoid by supplying it ignition voltage whenever exhaust gas needs to be recirculated into the intake manifold. The PCM monitors the EGR solenoid and position sensor circuits for correct voltage levels at certain times. The PCM also monitors the flow of exhaust gas through the EGR valve by using the MAP sensor. During deceleration, the EGR valve is normally closed. However, the PCM will run a flow test by opening the EGR valve and monitoring the change in the MAP signal voltage. DTC P0401 sets when the change in the MAP signal voltage is below a certain threshold when the EGR valve is being commanded On during the deceleration.

DTC PARAMETERS
DTC P0401 will set if the PCM determines EGR flow to be restricted based on engine speed and barometric pressure using the MAP sensor when:
^ Engine speed is between 1250 and 2600 RPM
^ VSS is greater than 56 km/h (35 mph)
^ Transaxle is in top gear
^ TP angle is 0% (vehicle in decel)
^ ECT is greater than 70°C (150°F)
^ No other cam, CKP, ECT EGR solenoid, 5 volt reference, IAC, IAT, MAP, misfire, TP or VSS DTCs have been set.

DTC P0401 diagnostic runs once per ignition cycle for 1 second during deceleration once the above conditions have been met.

DTC P0401 is a type B DTC.

DIAGNOSTIC AIDS
The most likely cause of this DTC is carbon buildup around the EGR valve or a blocked EGR passage.

Remove EGR valve and check for a blocked passage and for carbon buildup around the EGR pintle valve. Clean or replace EGR valve and/or clean EGR passage.