The Vehicle Speed Sensor (VSS) generates an AC signal as its coil is excited by rotation of the rear planetary carrier lugs. The Transmission Control Module (TCM) interprets this information as output shaft RPM.
Removal & Installation
- Raise and safely support the vehicle.
- Place a suitable catch pan under the transmission for any fluid.
- Remove the wiring connector from the output speed sensor.
- Remove the mounting bolt and remove the speed sensor from the transmission case.
- Install the speed sensor into the transmission case and tighten the bolt to 105 inch lbs. (12 Nm).
- Install the wiring connector to the speed sensor.
- Verify the proper transmission fluid level and refill as necessary.
- Lower the vehicle.
- Start the engine and allow it to reach normal operating temperature. Using a diagnostic scan tool, check for the presence of any Diagnostic Trouble Codes (DTCs). Record and address these codes as necessary.
- Refer to any Technical Service Bulletins (TSBs) that may apply.
- Review the scan tool Freeze Frame information. If possible, try to duplicate the conditions under which the DTC set.
- With the engine running at normal operating temperature, monitor the scan tool parameters related to the DTC while wiggling the wire harness. Look for parameter values to change and/or a DTC to set. Turn the ignition off.
Visually inspect the related wire harness. Disconnect all the related harness connectors. Look for any chafed, pierced, pinched, partially broken wires and broken, bent, pushed out, or corroded terminals.
Perform a voltage drop test on the related circuits between the suspected inoperative component and the ECM.
CAUTIONDo not probe the ECM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool No. 8815 to perform diagnosis.
- Inspect and clean all ECM, engine, and chassis grounds that are related to the most current DTC.
- If numerous trouble codes were set, use a wire schematic and look for any common ground or supply circuits.
- For any Relay DTCs, actuate the Relay with the scan tool and wiggle the related wire harness to try to interrupt the actuation.
- For intermittent Evaporative Emission trouble codes perform a visual and physical inspection of the related parts including hoses and the Fuel Filler cap.
- Use the scan tool to perform a System Test if one applies to failing component. A co-pilot, data recorder, and/or lab scope should be used to help diagnose intermittent conditions.