Circuit Description
The automatic transmission input shaft speed (AT ISS) sensor is a three-wire magnetic pick-up sensor that is mounted externally to the transmission. The AT ISS utilizes the main idler gear teeth, located on the mainshaft, to generate a voltage signal of varying frequency that corresponds to the rotational speed of the automatic transmission output speed shaft (AT OSS) sensor. The AT ISS signal is sent to the powertrain control module (PCM) and is used to calculate the vehicle speed. Simultaneously, the signal from the AT OSS is used to calculate the vehicle speed. The PCM compares the vehicle speed calculated from both speed sensors and uses this comparison for diagnosis of the speed sensors.
If the PCM detects a low AT ISS speed and a high AT OSS calculated vehicle speed for 10 seconds, DTC P0717 sets. DTC P0717 is a type A DTC.