Voltage is provided to the exhaust gas recirculation (EGR) valve by the ignition 1 voltage circuit through a fuse. Ground is provided to the EGR valve on the control circuit by a low side driver within the engine control module (ECM). The ECM monitors the voltage on the control circuit of the EGR valve to determine if a failure is present.

The engine control module (ECM) monitors the position of the exhaust gas recirculation (EGR) valve through the EGR valve position sensor. The EGR valve position sensor sends a feedback voltage on the signal circuit to the ECM. The EGR position sensor voltage varies depending on the position of the EGR valve.

The EGR valve utilizes the following circuits:

The ECM detects the difference between the actual EGR position and the learned EGR position is greater than 10 percent.

DTC P0488 is a Type B DTC.

DTC P0488 is a Type B DTC.

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Description and Operation

Exhaust Gas Recirculation (EGR) System Description

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

1. Ignition ON, observe the DTC information with a scan tool. Verify DTC P0651 is not set.

⇒	If DTC P0651 is set, refer to DTC P0641 or P0651 .

2. Observe the EGR Position Variance parameter while commanding the EGR valve to 100 percent. The reading should be less than 15 percent.
3. Engine running, observe the EGR position sensor percentage parameter. The reading should be less than 4 percent.
4. If the vehicle passes the Circuit/System Verification Test, then 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.

1. Ignition OFF, disconnect the harness connector of the EGR valve.
2. Ignition ON, verify that a test lamp illuminates between the ignition 1 voltage circuit and ground.

⇒	If the test lamp does not illuminate, test the ignition 1 voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition 1 voltage circuit fuse is open, test all components connected to the ignition 1 voltage circuit and replace as necessary.

3. Ignition OFF, verify a test lamp does not illuminate between the control circuit and B+.

⇒	If test lamp illuminates, test the control circuit for a short to ground. If the circuit/connections test normal, replace the ECM.

4. Ignition ON, With a scan tool, command the EGR valve to 100 percent. The test lamp should illuminate.

⇒	If test lamp does not illuminate, test the control circuit for a short to voltage or an open/high resistance. If the circuit/connections test normal, replace the ECM.

5. Ignition OFF, test for less than 1 ohm of resistance between the low reference circuit and ground.

⇒	If greater than 1 ohm, test the low reference circuit for an open/high resistance. If the circuit/connections test normal, replace the ECM.

Important: The 5-volt reference circuits are internally and externally connected at the ECM. Other component DTCs may be set. If other DTCs are set, review the electrical schematic and diagnose the applicable circuits and components.

6. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit and ground.

⇒	If less than 4.8 volts, test the 5-volt reference circuit for a short to ground or open/high resistance. If the circuit/connections test normal, replace the ECM.

⇒	If greater than 5.2 volts, test the 5-volt reference circuit for a short to voltage. If the circuit/connections test normal, replace the ECM.

7. Ignition ON, verify that the EGR position sensor parameter is less than 3 percent.

⇒	If greater than 3 percent, test the signal circuit for a short to voltage. If the circuit/connections test normal, replace the ECM.

8. Ignition ON, install a 3-amp fused jumper wire between the signal circuit and the 5-volt reference circuit. Verify that the EGR position sensor parameter is greater than 95 percent.

⇒	If less than 95 percent, test the signal circuit for a short to ground or an open/high resistance. If the circuit/connections test normal, replace the ECM.

9. If all circuits/connections test normal, test or replace the EGR valve.

1. Ignition OFF, disconnect the harness connector of the exhaust gas recirculation (EGR) valve.
2. Measure for 6-10 ohms of resistance between the ignition 1 voltage and control circuit terminal of the EGR valve.

⇒	If the resistance is out of the specified range, replace the EGR valve.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.