DTC Troubleshooting: P0503 (17-3)

DTC P0503:  VSS Signal Malfunction

1.Note this freeze data:
  • Engine speed
  • Vehicle speed

2.Clear the DTC with the HDS.

3.Start the engine, then let it idle.

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

Is DTC P0503 indicated?


YES - Go to 7.


NO - Go to 5.


5.Test-drive the vehicle for several minutes in the range of the recorded freeze data.

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

Is DTC P0503 indicated?


YES - Go to 7.


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


7.Reset the ECM with the HDS.

8.Check for poor or loose connections and terminals at the following:
  • VSS
  • ECM
  • Engine ground
  • Body ground

Are the connections and terminals OK?


YES - Go to 9.


NO - Repair the connectors or terminals, then go to 10.

9.Replace the VSS.

10.Turn the ignition switch ON (II).

11.Reset the ECM with the HDS.

12.Start the engine, then let it idle.

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

Is DTC P0503 indicated?


YES - Go to 16.


NO - Go to 14.


14.Test-drive the vehicle for several minutes in the range of the recorded freeze data.

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

Is DTC P0503 indicated?


YES - Go to 16.


NO - Troubleshooting is complete.n


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

17.Start the engine, then let it idle.

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

Is DTC P0503 indicated?


YES - If DTC P0503 is indicated, check for poor connections or loose terminals at the VSS and the ECM, then go to 1. If any other Temporary DTCs or DTCs are indicated, go to the indicated DTC's troubleshooting.


NO - Go to 19.

19.Test-drive the vehicle for several minutes in the range of the recorded freeze data.

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

Is DTC P0503 indicated?


YES - If DTC P0503 is indicated, check for poor connections or loose terminals at the VSS 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