P0403

DTC P0403

CIRCUIT DESCRIPTION
The engine control module (ECM) controls the EGR valve opening based on the atmospheric pressure, engine speed, engine coolant temperature, intake air temperature and fuel injection quantity. The ECM controls the EGR valve by controlling the EGR DC motor. The EGR valve position is detected by the EGR position sensor, and relayed to ECM via the EGR position sensor. If the ECM detects an electrical malfunction on the EGR motor circuits, this DTC will set.

Condition for Running the DTC
- DTCs P0642 and P0643 are not set.
- The battery voltage is between 10-16 volts.
- The ignition switch is ON for 2 seconds.
- The engine is running.
- The engine coolant temperature (ECT) is more than149 °F (65 °C).
- The EGR valve commanded duty cycle is between 5-95%.

Condition for Setting the DTC
- The ECM detects that the EGR valve control pulse width modulation (PWM) signal is not inputted.

Action Taken When the DTC Sets
12,000 lbs GVW
- The ECM illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
- The ECM records the operating conditions at the time the diagnostic fails. The ECM stores this information in the Freeze Frame/Failure Records.
- The ECM limits fuel injection quantity within 70%.
- The ECM closes the EGR valve and holds to close position.

Except 12,000 lbs GVW
- The ECM will not illuminate the MIL when the diagnostic runs and fails.
- The ECM records the operating conditions at the time the diagnostic fails. The ECM stores this information in the Failure Records.

Condition for Clearing the MIL/DTC
12,000 lbs GVW
- The ECM turns OFF the MIL after 3 consecutive driving cycles when the diagnostic runs and does not fail.
- A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
- A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic after the ECM turns OFF the MIL.
- Clear the MIL and the DTC with a scan tool.

Except 12,000 lbs GVW
- A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
- A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
- Clear the DTC with a scan tool.

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

Check for the following conditions:
- Poor connection at the 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 Current Position" display on the scan tool with engine running while moving connectors and wiring harness. A change in the display will indicate the location of the fault.

DTC P0403
Schematic Reference: Engine Controls Schematics
Connector End View Reference: Engine Controls Connector End Views or Engine Control Module (ECM) Connector End Views

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