Diagnostic Aids

Perform this test only when directed by QUICK TEST. This test is intended to diagnose the following:

• Wiring harness circuits (PSOM+ and PSOM-).
• Powertrain Control Module (PCM).
  Fig 1: Identifying PSOM Test Circuits & Connector Terminals

  

1. 1) DTCs P0500, P0501, P0503 & P1500: Check Sensor & Wiring Harness
   
   DTC P0500 indicates a Vehicle Speed Sensor (VSS) is out of range. DTC P0501 indicates that ABS sensor is out of range. DTC P0503 indicates electrical noise problems. DTC P1500 indicates intermittent sensor circuit failure. Possible causes for these faults are:
   • Wiring harness open or shorted circuits.
   • Faulty rear ABS sensor.
   • Faulty PSOM.
   • Faulty Speed Control Module.
   • Powertrain Control Module (PCM).

   Turn ignition off. Ensure rear ABS sensor and connector are correctly seated. Ensure wiring harness is not chafed, burnt or corroded. If any faults are found, service or repair as necessary. If no faults are found, go to next step.

2. 2) Check For Intermittent Circuit Fault
   
   Turn ignition off. Connect scan tester to DLC. Using scan tester, access VSS PID. Road test vehicle while recording VSS data. If possible, drive on rough, wet roads. Return to service area and review recorded PID data graph. If any blips are present, isolate fault in circuit. Repair as necessary and repeat QUICK TEST . If no blips are present, go to next step.
3. 3) Check Signal To Module
   
   Turn ignition off. Disconnect PCM 104-pin connector. Inspect connector for damaged and repair as necessary. Install EEC-V Breakout Box (014-00950). Connect PCM to breakout box. Set voltmeter on AC scale. Road test vehicle. Measure voltage between test pin No. 33 and 58 while gradually accelerating to 50 MPH. If maximum AC voltage is 4 volts or less, go to next step. If maximum AC voltage is more than 4 volts, replace PCM and repeat QUICK TEST .
4. 4) Check Circuit Resistance
   
   Turn ignition off. Disconnect PCM from breakout box. Disconnect PSOM and speed control module. Inspect connectors for damaged and repair as necessary. Measure resistance of PSOM(-) circuit between wiring harness connector terminal and test pin No. 33 at breakout box. Measure resistance of PSOM(+) circuit between wiring harness connector terminal and test pin No. 58 at breakout box. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open circuit and repeat QUICK TEST .
5. 5) Check Circuit For Short To Power & Ground
   
   Leave ignition off, PSOM and PCM disconnected. Measure resistance between test pin No. 58 and test pins No. 24, 33, and 71. If all resistance measurements are 10,000 ohms or more, fault is not in PSOM or related circuitry. Check instrument cluster, ABS or speed control system. If any resistance measurement is less than 10,000 ohms, repair short circuit and repeat QUICK TEST .