P0400

DTC P0400

Circuit Description
The exhaust gas recirculation (EGR) valve moves via the EGR valve motor and the EGR valve motor controlled by the engine control module (ECM). The EGR valve position sensor is installed on the EGR valve body together with the EGR valve control motor. The EGR valve position sensor changes output voltage according to EGR valve position. The EGR valve has the following circuits.
- EGR valve motor 12 volts feed circuit
- EGR valve motor duty signal circuit
- EGR valve 5 volts reference circuit
- EGR valve position sensor low reference circuit
- EGR valve position sensor signal circuit.

The ECM supplies 5 volts to the EGR valve position sensor on the 5 volts reference circuit. The ECM also provides a ground on the low circuit. The EGR valve position sensor provides a signal to the ECM on the EGR valve position signal circuit, which is relative to the position changes the EGR valve. The ECM monitors the EGR position sensor signals for voltage outside the normal range of the EGR position. If the ECM detects an excessively high EGR valve control duty cycle, this DTC will set.

Condition for Running the DTC
- The battery voltage is between 10-16 volts.
- The ignition switch is ON.
- The engine is running.
- The EGR control is normal.

Condition for Setting the DTC
- The ECM detects that the EGR valve control duty cycle is more than 70% for 8 seconds.

Action Taken When the DTC Sets
- The ECM illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
- The ECM limits fuel injection quantity within 70%.
- The ECM closes the EGR valve and stops EGR control.

Condition for Clearing the DTC
- A current DTC clears when the ignition is turned OFF.
- Clear the MIL and the DTC with a scan tool.

Diagnostic Aids
If an intermittent condition is suspected, the following may cause an intermittent:
- Poor connections.
- Misrouted harness.
- Rubbed through wire insulation.
- Broken wire inside the insulation.

Check for the following conditions:
- Poor connection at ECM: Inspect harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.
- Damaged harness: Inspect the wiring harness for damage. If the harness appears to be OK, observe the EGR Position or the EGR Position Sensor display on the scan tool while moving connectors and wiring harness related to the sensor. A change in the display will indicate the location of the fault.

Test Description
The number below refers to the step number on the diagnostic table.
3. Operate the vehicle within the same conditions as when the DTC failed. If you can not duplicate the DTC, use the information included in the Failure Records data can help to locate an intermittent condition.

DTC P0400

Schematic Reference: Engine Controls Schematics

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