P0403

CIRCUIT DESCRIPTION
The DTC P0403 Exhaust Gas Recirculation (EGR) Solenoid Control Circuit diagnostic monitors the electrical circuitry of the EGR valve. The EGR system controls the formation of Oxides Of Nitrogen (NOx) 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 4 coil windings that control the motor movement. The DTC P0403 diagnostic monitors the electrical circuits of the 4 coils.

CONDITIONS FOR SETTING THE DTC
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.

ACTION TAKEN WHEN THE DTC SETS
^ The PCM illuminates the Malfunction Indicator Lamp (MIL) after 2 consecutive ignition cycles in which the diagnostic runs with the fault active.
^ The PCM records the operating conditions at the time the diagnostic fails. This information is stored in the Freeze Frame buffer.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The MIL turns OFF after 3 consecutively passing trips without a fault present.
^ A history DTC clears after 40 consecutive warm-up cycles without a fault.
^ Perform the scan tool Clear DTC Information function in order to clear the DTC.

DIAGNOSTIC AIDS
A normal engine operating temperature is specified as 80°C (176°F) or more.

Check for any of the following conditions:
^ An incorrect PCM can cause DTC P0403 to set. Verify that the correct PCM is installed in the vehicle as required for proper emission certification.
^ A faulty electrical connection at the PCM.

An intermittent malfunction may be caused by a fault in the EGR control system electrical circuits. Inspect the wiring harness and the components for an intermittent condition. Refer to Intermittent Conditions. Intermittent Conditions

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

EGR Valve Terminal (Pin) Identification:

Use the above 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.

TEST DESCRIPTION

Steps 1-8:

Steps 9-12:

The numbers below refer to the step numbers on the diagnostic table.
1. The Diagnostic System Check-Computers and Control Systems 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, 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 DTC P0403 DOES NOT reset within 1 minute, the circuits referred to in Step 6 or the PCM are at fault.