The exhaust gas recirculation (EGR) valve is controlled by the engine control module (ECM) through the EGR solenoid. Ignition 1 voltage is supplied directly to the EGR valve solenoid. The ECM controls the solenoid by grounding the control circuit. When the EGR solenoid is commanded ON, vacuum from the vacuum pump is applied to the EGR valve.

P0401

The ECM detects the EGR flow is below a calibrated amount when the EGR is commanded ON.

P0402

The ECM detects the EGR flow is above a calibrated amount when the EGR is commanded OFF.

DTCs P0401, and P0402 are Type B DTCs.

DTCs P0401, and P0402 are Type B DTCs.

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Special Tools Required

J 23738-A Mity Vac

1. Ignition ON, observe the diagnostic trouble code (DTC) information with a scan tool. Verify that no other DTCs are set.

⇒	If any other DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle for further diagnosis.

2. With a scan tool command the throttle blade from 0-100 percent. The throttle blade should respond to the scan tool commands.

⇒	If the throttle body does not respond to the scan tool commands, refer to DTC P02E0, P02E2, or P02E3 for further diagnosis.

3. With a scan tool command the EGR solenoid valve from 0-100 percent. The EGR solenoid should respond to the scan tool commands.

⇒	If the EGR solenoid does not respond to the scan tool commands, refer to DTC P0403, P0489, or P0490 for further diagnosis.

4. Operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records List. DTCs P0401, or P0402 should not set.

1. Ignition OFF, inspect for the following:

•	Intake system/charge air hoses for leaks/restrictions

•	Exhaust system/turbo charger for leaks/restrictions

•	Vacuum supply system for leaks or blockage

•	Air filter for restrictions

2. Disconnect the vacuum source from the EGR solenoid.
3. Connect the J 23738-A to the EGR solenoid vacuum supply hose. Engine idling, verify the vacuum is greater than 20 in Hg.

⇒	If less than the specified range, inspect the vacuum supply hose and filter for a leak or restriction. If the supply hose is OK, replace the vacuum pump.

4. Connect the vacuum source to the EGR solenoid valve. Connect the J 23738-A to the EGR vacuum port on the EGR solenoid valve. Engine idling, command the EGR solenoid valve to 5 percent with a scan tool. Verify the vacuum is at 0 in Hg.

⇒	If the vacuum is greater than the specified range, replace the EGR solenoid valve.

5. Command the EGR solenoid valve to 100 percent with a scan tool. Verify the vacuum is greater than 20 in Hg.

⇒	If the vacuum is less than the specified range, test the ignition voltage circuit and the EGR solenoid control circuit for greater than 5 ohms of resistance. If the circuits test normal, replace the EGR solenoid valve.

6. Connect the J 23738-A to the EGR valve vacuum hose. Apply 10 in Hg of vacuum to the EGR valve. Verify the EGR valve operation.

⇒	If the EGR valve does not operate, inspect the vacuum hose for leaks or restrictions. If no leaks or restrictions are found, replace the EGR valve.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.