Vehicle Speed Signal Circuit Troubleshooting
Vehicle Speed Signal Circuit TroubleshootingSpecial Tools Required: Test Harness 07LAJ-PT3020A
Before testing, inspect the No. 4 (7.5 A) fuse in the under-dash fuse/relay box.
1. Disconnect the 3P connector from the VSS (vehicle speed sensor) (A).
2. Connect the test harness only to the engine wire harness.
3. Connect the RED test harness clip (B) to the positive prove of an ohmmeter. Cover the white (C) and green (D) test harness with protective tape (E).
4. Check for continuity between the RED test harness clip and body ground.
Is there continuity?
YES - Go to step 5.
NO - Repair open in the BLK wire between the VSS and G101.
5. Connect the WHT test harness clip (C) to the positive probe of a voltmeter, and connect the RED test harness clip (B) to the negative probe.
6. Turn the ignition switch ON (II).
Is there battery voltage?
YES - Go to step 7.
NO - Repair open in the BLK/YEL wire between the VSS and the under-dash fuse/relay box.
7. Disconnect the WHT test harness clip (C).
8. Connect the GRN test harness clip (D) to the positive probe of a voltmeter.
Is there 5 V or more?
YES - Go to step 9.
NO - Repair short in the BLU/WHT wire between the VSS and the ECM.
9. Turn the ignition switch OFF.
10. Connect the other test harness connector (A) to the VSS (B).
11. Raise the front of the vehicle, and make sure it is securely supported.
12. Put the vehicle in neutral with the ignition switch ON (II).
13. Slowly rotate one wheel with the other wheel blocked.
Does voltage pulse from 0 to approx. 5 V or more?
YES - Go to step 14.
NO - Replace the VSS.
14. Disconnect the 30P connector "A" from the gauge assembly.
15. Connect a voltmeter between the BLU/WHT wire and body ground.
16. Slowly rotate one wheel with the other wheel blocked.
Does the meter indicate pulsing voltage?
YES - Replace the speedometer.
NO - Repair open in the BLU/WHT wire between the VSS and the speedometer.