77-1

VTM-4 DTC Troubleshooting: 77-1

DTC 77-1: PCM

NOTE:

- Before you troubleshoot, review the general troubleshooting information. Initial Inspection and Diagnostic Overview

- Check the fuel and emissions system DTCs. If there is a DTC, troubleshoot the indicated DTC first, then troubleshoot DTC 77.

1. Turn the ignition switch to ON (II).

2. Make sure the HDS communicates with the vehicle and the VTM-4 control unit. If it doesn't, troubleshoot the DLC circuit. Testing and Inspection

3. Clear the DTC with the HDS.

4. Test-drive the vehicle, and check for DTCs with the HDS.

Is DTC 77-1 indicated?
YES - Go to step 5.

NO - Intermittent failure, the system is OK at this time.


5. Update the PCM if it does not have the latest software, PCM Update or substitute a known-good PCM. Initial Inspection and Diagnostic Overview

6. Test-drive the vehicle, and check for DTCs with the HDS.

Is DTC 77-1 indicated?
YES - Check for loose terminal fit in the VTM-4 control unit. If it is normal, substitute a known-good VTM-4 control unit Service and Repair and recheck. If the symptom/indication goes away with the known-good VTM-4 control unit, replace the original VTM-4 control unit. Service and Repair

NO - If the PCM was updated, troubleshooting is complete. If the PCM was substituted, replace the original PCM. Service and Repair