| CAUTION | If ECM replacement is instructed in following testing, always ensure ECM connectors and ground circuit are okay. If either are suspect, repair and repeat testing to confirm ECM malfunction. If ECM is replaced, ECM must be programmed with proper ignition key code for engine immobilizer system (if equipped). For programming procedures, see COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION. |
Circuit Description
Instrument cluster gets vehicle speed signal from ABS control module. A 4-pulse 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 vehicle speed signal to ECM while vehicle is being driven and park/neutral switch is off. Possible causes are
- Defective ABS ECU.
- Vehicle speed sensor signal from instrument cluster 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.