Preliminary Instructions

Record and clear continuous memory codes. Warm engine to normal operating temperature. Place gear selector in Drive position. Accelerate hard to 35 MPH and coast down to a stop. Shut off engine. Perform KOEO SELF-TEST  . Repeat procedure at least 2 more times. Go to step 1).

1. Continuous Memory Code 452
   
   Code 452 indicates PCM detected incorrect output from VSS sometime during vehicle operation. Possible causes for this code are:
   • Faulty VSS.
   • Open or shorted circuit.
   • Faulty PCM.

   Perform appropriate TRANSMISSION DRIVE CYCLE TEST. Ensure driveability complaint can be verified. If Code 452 is still present or driveability complaint can be verified, go to step 2). If code is not present or complaint cannot be verified, fault cannot be duplicated at this time. Clear codes, and see SYMPTOMS in the appropriate TESTS W/O CODES article in the ENGINE PERFORMANCE section.

2. Check VSS Circuit Continuity
   
   Turn ignition off. Disconnect VSS sensor. Remove PCM 60-pin connector. Inspect terminals, and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV). Measure resistance between VSS (+) terminal at VSS wiring harness connector and test pin No. 3 at breakout box. Measure resistance between VSS (-) terminal at VSS wiring harness connector and test pin No. 6 at breakout box. If any resistance reading is more than 5 ohms, service open circuit in VSS wiring harness and repeat step 1). If both resistance readings are 5 ohms or less, go to step 3).
3. Check VSS Circuits For Shorts To Power or Ground
   
   Turn ignition off. Ensure PCM and VSS are disconnected. Measure resistance between test pin No. 3 and test pins No. 6, 37 and 40 at breakout box. If all readings are greater than 500 ohms, go to step 4). If any reading is less than 500 ohms, repair shorts in VSS wiring harness and repeat step 1).
4. Check VSS Resistance
   
   Turn ignition off, and wait 10 seconds. Disconnect VSS wiring harness connector. Measure resistance across VSS terminals. If reading is not 190-250 ohms, replace VSS and repeat step 1). If resistance is 190-250 ohms, replace PCM and repeat step 1).