| CAUTION | If ECM replacement is instructed in following tests, always ensure ECM connectors and ground circuit are okay. If either are suspect, repair and repeat testing to confirm ECM malfunction. |
Note. For component location, see appropriate illustration in THEORY & OPERATION article.
Circuit Description
VSS outputs a 4-pulse signal for every revolution of rotor shaft, which is driven by transaxle output shaft. Signal is sent to instrument cluster to operate speedometer. Instrument cluster then sends signal to ECM. Signal is used by ECM to determine vehicle speed. DTC is set if there is no VSS signal to ECM while vehicle is being driven and park/neutral switch is off. Possible causes are
- Defective vehicle speed sensor.
- Vehicle speed sensor circuit is open or shorted.
- Defective instrument cluster.
- Defective ECM.
Diagnostic Aids
Using scan tool, read freeze frame data. Freeze frame records engine conditions when malfunction is detected.