Test N - Vehicle Speed Sensor (VSS): Notes

To prevent replacement of good components, be aware that the following circuit test is to be used only when continuous codes 27 or 29 are displayed. This test checks vehicle speed sensor, wiring harness, and ECA.

1. On Automatic Transmission Equipped Vehicles. Record and clear CONTINUOUS SELF-TEST codes. Warm engine to normal operating temperature. While in first gear accelerate moderately to 25 MPH and coast down to idle and stop. Shut off engine. Perform KEY OFF/ENGINE ON (KOEO) SELF-TEST. If code 29 is present, go to step 3). If not, fault cannot be duplicated at this time. If any other codes are present, return to QUICK TEST  . If codes are not present, test is completed.
2. On Manual Transmission Equipped Vehicles. Record and clear CONTINUOUS SELF-TEST codes. Warm engine to normal operating temperature. Start in first gear, shift to second gear, and accelerate moderately to 40 MPH. Coast down to idle and stop. Shut engine off. Perform KOEO SELF-TEST. If code 29 is present, go to next step. If not, fault cannot be duplicated at this time. If any other codes are present, return to QUICK TEST  . If codes are not present, test is completed.
3. Turn key off and wait 10 seconds. Disconnect vehicle speed sensor. Set DVOM on 200,000-ohm scale. Measure resistance across vehicle speed sensor. If reading is between 190-230 ohms, go to next step. If reading is incorrect, replace vehicle speed sensor and repeat step 1).
4. Turn key off and wait 10 seconds. Remove ECA 60-pin connector and inspect for damaged pins, corrosion, or loose wires. Repair as necessary. Install breakout box. With ECA and VSS disconnected, set DVOM on 200-ohm scale. Measure resistance between test pin No. 3 at breakout box and VSS harness connector. Also measure resistance between test pin No. 6 at breakout box and VSS harness connector. If both readings are 5 ohms or less, go to next step. If readings are 5 ohms or more, service open circuit in VSS wiring harness. After repairs, repeat step 1).
5. Turn key off. With ECA and VSS disconnected, set DVOM on 200,000-ohm scale. Measure resistance between test pin No. 3 and test pins No. 37, 40 and 6 at breakout box. Also measure resistance between test pin No. 6 and test pins No. 37 and 40. If all readings are greater than 10,000 ohms, go to next step. If any reading is less than 10,000 ohms, repair short(S) in VSS wiring harness. After repairs, repeat step 1).
6. Substitute VSS with known good sensor. Connect ECA and VSS. Repeat step 1), then return to this step. If code 29 is present, replace ECA and repeat step 1). If no code is present, replace original vehicle speed sensor.