Automatic Transmission Input Shaft Speed and Output Shaft Speed Sensors
Both of the AT ISS and the AT OSS sensors are magnetic induction sensors. The input and the output sensors are accessible from the left hand side of the transmission. The AT ISS sensor is located just forward of center and the AT OSS sensor is located near the rear. A voltage signal is induced in the AT 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 PCM/TCM uses speed information from these sensors in order to determine the following conditions:
- Whether the engine is running
- Vehicle speed
- Calculation of the gear ratio
- Calculation of TCC slip
- Calculation of turbine speed
Code P0502 and P0503 set if a fault exists in the AT OSS sensor circuit, and the PCM/TCM calculates a default value using the AT ISS sensor values. As long as the fault remains, and the code is set, the PCM/TCM also commands maximum line pressure, freeze shift adapts, and the MIL illuminates. If the fault is removed, normal operation resumes after the next ignition cycle.