78-1

VTM-4 DTC Troubleshooting: 78-1

DTC 78-1:

VTM-4 Control Unit

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

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

2. Clear the DTC with the HDS.

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

Is DTC 78-1 indicated?

YES -

Go to step 4.

NO -

Intermittent failure, the system is OK at this time.�

4. Check the battery Testing and Inspection.

Is the specified battery installed, and is it fully charged?

YES -

Go to step 5.

NO -

Replace or charge the battery Removal and Replacement.�

5. Check the charging system indicator.

Does the charging system indicator come on with the ignition switch ON (II), and go off with the engine started?

YES -

Go to step 6.

NO -

Do the charging system troubleshooting Charging System Indicator Circuit Troubleshooting.�

6. Check for installation of any aftermarket CB or Ham radios which may cause an RF signal interference.

Is there an aftermarket radio installed?

YES -

Disconnect the aftermarket radio, and retest.�

NO -

Check for poor connections or loose terminals at the VTM-4 control unit connectors. If the connections are OK, 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.�