Faulty Output Shaft (Countershaft) Speed Sensor
Output Shaft Speed Sensor harness is open or shorted
Output Shaft Speed Sensor circuit poor electrical connection
Faulty Engine Control Module (ECM)
Engine Light ON (or Service Engine Soon Warning Light)
Speedometer improper reading
Possible shifting problems
The Output Shaft (Countershaft) Speed Sensor is attached to the transmission housing to sense countershaft revolutions. The Engine Control Module (ECM) determines the vehicle speed according to the signal from the Output Shaft (Countershaft) Speed Sensor to the control units. If no signal from the Output Shaft (Countershaft) Speed Sensor is received for a set period of time, the ECM detects a malfunction, and a Diagnostic Trouble Code (DTC) is stored.