Vehicle Speed Signal Circuit Troubleshooting

Special Tools Required: 

Test Harness 07LAJ-PT3020A

Before testing, inspect the No. 4 (10A) and No. 10 (7.5A) fuses in the under-dash fuse/relay box.

1. Disconnect the 3P connector from the vehicle speed sensor (VSS) (A).
   Fig 1: Disconnecting Connector From VSS

   
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? 

   1. YES  - Go to step 5.
   2. NO  - Repair open in the BLK wire between the VSS and G101.
5. Connect the WHT test harness clip (B) to the positive probe of a voltmeter, and connect the RED test harness clip (C) to the negative probe.
   Fig 2: Connecting WHT Test Harness Clip To Probe

   
6. Turn the ignition switch ON (II).

   Is there battery voltage? 

   1. YES  - Go to step 7.
   2. 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 (B).
8. Connect the GRN test harness clip (D) to the positive probe of a voltmeter.
   Fig 3: Connecting GRN Test Harness Clip To Probe

   

   Is there 5 V or more? 

   1. YES  - Go to step 9.
   2. NO  - Repair short in the BLU/WHT wire between the VSS and the cruise control unit, or the ECM/PCM.
9. Turn the ignition switch OFF.
10. Connect the other test harness connector (A) to the VSS (B).
    Fig 4: Connecting Other Test Harness Connector To VSS

    
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 about 5 V or more? 

    1. YES  - Go to step 14.
    2. NO  - Replace the VSS.
14. Disconnect the 22P connector "A" from the gauge assembly.
    Fig 5: Disconnecting Connector "A" From Gauge Assembly

    
15. Touch a probe to the BLU/WHT wire, and connect it to body ground through a voltmeter.
16. Slowly rotate one wheel with the other wheel blocked.

    Does the voltmeter indicate pulsing voltage? 

    1. YES  - Replace the speedometer assembly.
    2. NO  - Repair open in the BLU/WHT wire between the VSS and the speedometer.