Diagnostic Aids

Ensure speedometer is functioning properly before performing this test. If speedometer does not function properly, repair speedometer as necessary. See ANALOG INSTRUMENT PANELS - VILLAGER article in ACCESSORIES & EQUIPMENT. Perform this test when directed by QUICK TEST. This test is intended to diagnose the following:

• Vehicle Speed Sensor (VSS).
• VSS harness circuit.
• PCM.

1. 1) DTC P0500
   
   This code indicates PCM detected incorrect output from VSS sometime during vehicle operation. Possible causes for this code are as follows:
   • Faulty VSS.
   • Faulty speedometer.
   • Open or short in harness.
   • Faulty PCM.

   Turn ignition off. Raise and support vehicle with drive wheels off the ground. Connect New Generation Star (NGS) tester to DLC. Start engine. Using NGS tester, access VSS PID. Place transmission in Drive. Release brakes. Observe VSS PID. VSS PID should match speedometer reading (within 10 percent). If VSS PID and speedometer appear to be correct, go to step  10). If speedometer appears to be correct but VSS PID is inaccurate, go to next step. If speedometer does not operate, repair speedometer before continuing diagnosis. See ANALOG INSTRUMENT PANELS - VILLAGER article in ACCESSORIES & EQUIPMENT.

2. 2) Check VSS Circuits For Open
   
   Turn ignition off. Disconnect PCM harness connector. Disconnect instrument cluster connector. Measure VSS circuit between PCM harness connector and instrument cluster harness connector. See Fig 1. See CIRCUIT PIN IDENTIFICATION  table. If resistance is less than 100 ohms, go to next step. If resistance is not less than 100, repair open in circuit. Reconnect all electrical connections and go to step  10).
   Fig 1: Identifying Vehicle Speed Sensor Circuit & Connector Terminals

   Courtesy of FORD MOTOR CO.
3. 3) Check VSS Circuits For Short To Ground
   
   Leave PCM and instrument cluster harness connector disconnected. Measure resistance between VSS and GND, SIG RTN and VPWR circuits at PCM harness connector. If all resistance measurements are greater than 10 k/ohms, go to next step. If any resistance measurement is not greater than 10 k/ohms, repair short in circuit, then go to step  10).
4. 4) Check VSS Circuit Continuity
   
   Disconnect VSS and instrument cluster harness connector. Measure resistance of VSS circuit between VSS harness connector and instrument cluster connector. If resistance is less than 5 ohms, go to next step. If resistance is not less than 5 ohms, repair open in circuit.
5. 5) Check VSS Circuit For Short-To-Ground
   
   Measure resistance between VSS circuit at instrument cluster harness connector and ground. If resistance is greater than 10 k/ohms, go to next step. If resistance is not greater than 10 k/ohms, repair short in circuit.
6. 6) Check VSS Output Signal
   
   Remove VSS from transaxle. Connect a voltmeter set on AC scale to VSS terminals. Measure AC voltage while quickly turning VSS pinion gear. If voltage reading is about .5 volt, replace PCM. If voltage reading is not about .5 volt, replace VSS.
   NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 6)  to step 10)  . No test procedures have been omitted.
7. 10) VSS Drive Cycle Test
   
   Start and warm engine to normal operating temperature. Perform entire drive cycle test 3 times. Place transmission in Drive. Accelerate quickly to 35 MPH. Coast to idle and stop vehicle. Turn off engine. Perform QUICK TEST . If any DTCs are present, repair as necessary. If no DTCs are present, VSS circuit is okay.