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Home >> Ford >> 1992 >> Crown Victoria Base, AOD >> Repair and Diagnosis >> Transmission >> Automatic Trans >> Diagnosis - AOD-E >> Circuit Tests >> Circuit Test DP Vehicle Speed Sensor (VSS) >> Preliminary Instructions

Preliminary Instructions

Record and clear continuous memory codes. Warm engine to normal operating temperature. In Low gear, accelerate hard to 35 MPH and coast down to a stop. Shut off engine. Perform KOEO SELF-TEST  . Go to step 1).

  1. 1) Continuous Memory Code 452  Code 452 indicates ECA detected incorrect output from VSS sometime during vehicle operation. Possible causes for this code are as follows:
    • Faulty VSS
    • Open Or Shorted Circuit
    • Faulty ECA

    Perform appropriate drive cycle procedure. See PRELIMINARY INSTRUCTIONS. 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 TROUBLE SHOOTING in AUTO TRANS OVERHAUL - FORD AOD article.

  2. 2) Check VSS Circuit Continuity  Turn ignition off. Disconnect VSS sensor. Remove ECA 60-pin connector. Inspect terminals and repair if damaged. Install EEC-IV Breakout Box (T83L-50-EEC-IV). Measure resistance between VSS DIF (+) terminal at VSS wiring harness connector and test pin No. 3 at breakout box. Measure resistance between VSS DIF (-) 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. 3) Check VSS Circuits For Shorts To Power Or Ground  Turn ignition off. Ensure ECA and VSS are disconnected. Set DVOM on 200-k/ohm scale. 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 next step. If any reading is less than 500 ohms, repair shorts in VSS wiring harness and repeat step 1).
  4. 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 ECA and repeat step 1).
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