Input (Shaft) Speed, Output (Shaft) Speed Sensors

Both of the Automatic Transmission Input (Shaft) Speed (A/T ISS) and the Automatic Transmission Output (Shaft) Speed (A/T OSS) Sensors are magnetic induction sensors. The input and the output sensors are accessible from the left hand side of the transmission. The A/T ISS Sensor is located just forward of center and the A/T OSS Sensor is located near the rear. A voltage signal is induced in the A/T ISS Sensor by serrations which are cut in the outside diameter of the forward clutch housing. Voltage is induced in the output sensor by gear teeth which are pressed on the outside diameter of the rear carrier assembly. The A/T OSS may be thought of as replacing the governor. Also note that the output speed may differ from speedometer readings because the A/T OSS Sensor reading is not corrected for minor variations in axle ratio or tire size.

The VCM/PCM used speed information from these sensors in order to determine the following:
- Whether the engine is running
- Vehicle speed
- Calculation of the gear ratio
- Calculation of TCC slip
- Calculation of turbine speed

If the A/T ISS Sensor is not operational at start up, and if the sensor reads 0, then the A/T OSS Sensor will also read 0. No direct code is associated with an A/T ISS Sensor fault. But an inaccurate A/T ISS Sensor could cause other codes to set, especially those associated with ratios or with slip.

Code P0502 will set if a fault exists in the A/T OSS Sensor circuit, and the VCM/PCM will calculate a default value using the A/T ISS Sensor values. As long as the fault remains and the code is set, the VCM/PCM will also command maximum line pressure, freeze shift adapts, and will not illuminate the MIL. if the fault is removed, normal operation will resume after the next ignition cycle.