The exhaust gas recirculation (EGR) system controls the formation of NOx (Oxides of Nitrogen) emissions by recirculating the exhaust gases into the combustion chamber. The EGR valve is a stepper motor design. The stepper motor moves a spring loaded plunger that controls the flow of exhaust gases into the intake manifold. The plunger movement is controlled by the powertrain control module (PCM). By turning the stepper motor in different directions, the PCM controls the opening of the exhaust gas passage to the intake manifold. The stepper motor has four coil windings that control the motor's movement. The DTC P0403 diagnostic monitors the electrical circuits of the four coils.

The voltage observed by the PCM on the EGR valve coil control circuits is not within the expected values when the ignition is ON.

OR

The voltage observed by the PCM on the EGR valve coil control circuits is not within the expected values, when the engine is running and the PCM requests the EGR valve ON.

Normal engine operating temperature is specified as 80°C (176°F) or above.

Check for any of the following conditions:

An intermittent malfunction may be caused by a fault in the EGR control system electrical circuits. Inspect the wiring harness and components for any of the following conditions:

If the DTC P0403 is intermittent, driving the vehicle under the following conditions can verify whether the fault is present. Perform the scan tool Clear DTC Information function. Road test the vehicle while monitoring the DTC P0403 diagnostic on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If a DTC P0403 appears in the Not Ran Since Code Cleared list, the P0403 diagnostic has not yet run. When the DTC P0403 does not appear in the Not Ran Since Code Cleared list, the P0403 diagnostic has run. If the MIL is NOT ILLUMINATED and there is no PENDING DTC Status in DTC Information, the P0403 diagnostic has passed. DTCs MUST BE CLEARED in order to view the CURRENT STATUS of the Not Ran Since Code Cleared list. DO NOT FORGET that the Not Ran Since Code Cleared list only indicates that the test has run, not whether the test passed or failed. The DTC Information screen must be checked for CURRENT or PENDING status, in order to determine the outcome of the diagnostic test involved.

If you cannot duplicate a DTC P0403, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.

Use the following table in order to locate the correct terminals to test during diagnosis. The table layout corresponds to the pin location of the EGR valve electrical terminals.

The numbers below refer to the step numbers on the diagnostic table.

1. The Powertrain OBD System Check prompts the technician to complete some basic checks and to store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

2. This step checks the ignition positive voltage supply to the EGR coils.

4. This step tests the operation of the EGR valve. If the EGR valve responds to commands from the scan tool, and the engine reacts to the valve opening, then the system is operating normally at this time.

5. This step determines which EGR coil control circuits may be at fault. If a DTC P0403 resets within 1 minute, the circuits referred to in step 8 or the PCM are at fault. If a DTC P0403 DOES NOT reset within 1 minute, the circuits referred to in step 6 or the PCM are at fault.