DTC Troubleshooting: P1623 (0-21)

DTC P1623:  ECM Power Source Circuit Unexpected Voltage

1.Turn the ignition switch ON (II).

2.Clear the DTC with the HDS.

3.Turn the ignition switch OFF, and wait 1 minute.

4.Turn the ignition switch ON (II).

5.Check for Temporary DTCs or DTCs with the HDS.

Is DTC P1536 or P1623 indicated?


YES - Go to 6.


NO - Intermittent failure, system is OK at this time. Check for poor connections or loose terminals at PGM-FI main relay 1 and the ECM.n


6.Turn the ignition switch OFF.

7.Disconnect PGM-FI main relay 1 and PGM-FI main relay 2.

8.Check PGM-FI main relay 1.

Is PGM-FI main relay 1 OK?


YES - Go to 9.


NO - Replace PGM-FI main relay 1, then go to 13.


9.Disconnect ECM connector No. 2 (58P).

10.Check for continuity between ECM connector No. 2 terminal No. 19 and body ground.

 

Is there continuity?


YES - Repair short in the wire between PGM-FI main relay 1, PGM-FI main relay 2 and ECM connector No. 2 terminal No. 19, then go to 12.


NO - Go to 11.


11.Measure voltage between ECM connector No. 2 terminal No. 1 and body ground.

 

Is there battery voltage?


YES - Repair short to power in the wire between PGM-FI main relay 1 and ECM connector No. 2 terminals No. 1, No. 3 or No. 5, then go to 12.


NO - Go to 16.

12.Reconnect all connectors.

13.Turn the ignition switch ON (II).

14.Reset the ECM with the HDS.

15.Check for Temporary DTCs or DTCs with the HDS.

Are any Temporary DTCs or DTCs indicated?


YES - If DTC P1623 is indicated, check for poor connections or loose terminals at PGM-FI main relay 1 and ECM, then go to 1. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC's troubleshooting.


NO - Troubleshooting is complete.n


16.Update the ECM if it does not have the latest software, or substitute a known-good ECM.

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

Are any Temporary DTCs or DTCs indicated?


YES - If DTC P1623 is indicated, check for poor connections or loose terminals at PGM-FI main relay 1 and the ECM, then go to 1. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC's troubleshooting.


NO - If the ECM was updated, troubleshooting is complete. If the ECM was substituted, replace the original ECM.n