Diagnostic Aids
Perform this test when directed by QUICK TEST. This test is intended to diagnose:
- ECA.
- Vehicle Speed Sensor (VSS).
- VSS harness circuits.
| Application | Wire Color |
|---|---|
| Pin No. 3 (VSS +) | Gray/Black |
| Pin No. 6 (VSS -) | Purple/Orange |
Preliminary Instructions (A/T Models) - Record and clear Continuous Memory Codes. Warm engine to normal operating temperature. In Low gear, accelerate hard to 35 MPH, then coast down to idle and stop. Shut engine off. Perform KOEO SELF-TEST, and record Continuous Memory Codes. Go to step 1).
Preliminary Instructions (M/T Models) - Record and clear Continuous Memory Codes. Warm engine to normal operating temperature. Start in 1st gear, shift to 2nd gear and accelerate moderately to 40 MPH. Coast down to idle and stop. Shut engine off. Perform KOEO SELF-TEST, and record Continuous Memory Codes. Go to step 1).
1) Continuous Memory Code 29/452 - Code 29/452 indicates during last 40 to 80 warm-up cycles, ECA detected fault in VSS output signal. Possible causes for this fault are as follows.
- Faulty ECA
- Faulty VSS
- Open Or Shorted Circuit
Perform appropriate drive cycle procedure. See PRELIMINARY INSTRUCTIONS (A/T MODELS) or PRELIMINARY INSTRUCTIONS(M/T MODELS). If Code 29 or 452 is still present, go to next step. If Code 29 or 452 is not present, clear continuous memory and see INTERMITTENTS in TESTS W/O CODES article.
2) Check VSS Circuit Continuity - Turn ignition off. Disconnect and inspect ECA 60-pin connector. With breakout box installed. disconnect ECA. Disconnect Vehicle Speed Sensor (VSS). Measure resistance between test pin No. 3 at breakout box and VSS DIF (+) circuit at VSS vehicle harness connector. Measure resistance between test pin No. 6 at breakout box and VSS DIF (-) circuit at vehicle harness connector. If all resistance readings are less than 5 ohms, go to next step. If any resistance reading is greater than 5 ohms, repair open in circuit. Remove breakout box, reconnect all components and repeat step 1).
3) Check VSS Circuits For Shorts To Power Or Ground - Turn ignition off. Disconnect Vehicle Speed Sensor (VSS). With breakout box installed, disconnect ECA. Measure resistance between test pin No. 3 and test pins No. 6, 37 and 40 at breakout box. If all resistance readings are greater than 500 ohms, reconnect ECA and go to next step. If any resistance reading is less than 500 ohms, repair short in circuit. Remove breakout box, reconnect all components and repeat step 1).
4) Checking VSS Resistance - Turn ignition off. Disconnect Vehicle Speed Sensor (VSS). Measure resistance across vehicle speed sensor. If resistance is 190-250 ohms, replace ECA. Remove breakout box, reconnect VSS and repeat step 1). If resistance is less than 190 ohms or greater than 250 ohms, replace VSS. Remove breakout box, and repeat step 1).