Theory Of Operation

The purpose of the diagnostic is to check if the output speed sensor signal is rational by monitoring for either a missing or invalid speed sensor signal. The output speed sensor is a Hall Effect sensor with an output range that alternates between normal high and normal low voltages as the output shaft tone wheel rotates. The following rationality check is performed by the TCM:

• Maximum Negative Gradient:  If the output speed sensor signal decelerates at a rate greater than a threshold, a fault code will be set.