DTC Troubleshooting: P0490 (12)

DTC P0490:  EGR Valve Circuit High Voltage

1.Turn the ignition switch ON (II).

2.Do the DTC CLEAR in the CLEAR MENU with the HDS.

3.Start the engine.

4.Check for Temporary DTCs or DTCs in the DTCs MENU with the HDS.

Is STC P0490 indicated?


YES - Go to 5.


NO - Intermittent failure, system is OK at this time. Check for poor connections or loose terminals at the EGR valve and the ECM.n


5.Turn the ignition switch OFF, and wait 10 seconds.

6.Disconnect the EGR valve 6P connector.

7.Connect the ECM test harness and the test pin box to the wire harness only, not to the ECM.

8.Turn the ignition switch ON (II).

9.Measure voltage between test pin box terminal No. 124 and body ground.

Is battery voltage?


YES - Repair short to power in the wire between the ECM connector No. 5 terminal No. 3 (test pin box terminal No. 124) and the EGR valve, then go to 11.


NO - Go to 10.


10.Measure voltage between test pin box terminal No. 126 and body ground.

Is there battery voltage?


YES - Repair short to power in the wire between the ECM connector No. 5 terminal No. 5 (test pin box terminal No. 126) and the EGR valve, then go to 11.


NO - Go to 18.

11.Turn the ignition switch OFF.

12.Reconnect all connectors.

13.Turn the ignition switch ON (II).

14.Do the ECM RESET in the CLEAR MENU with the HDS.

15.Do the ETCS learn procedure.

16.Start the engine.

17.Check for Temporary DTCs or DTCs in the DTCs MENU with the HDS.

Are any Temporary DTCs or DTCs indicated?


YES - If DTC P0490 is indicated, check for poor connections or loose terminals at the EGR Valve and the ECM, then go to 1. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC troubleshooting.


NO - Troubleshooting is conmplete.n


18.Substitute a known-good ECM.

19.Start the engine.

20.Check for Temporary DTCs or DTCs in the DTCs MENU with the HDS.

Are any Temporary DTCs or DTCs indicated?


YES - If DTC P0490 is indicated, check for poor connections or loose terminals at the EGR Valve and the ECM, then go to 1. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC troubleshooting.


NO - Replace the original ECM.n