Theory Of Operation

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

• Maximum Negative Gradient:  If the turbine speed sensor signal decelerates at a rate greater than a calibrated value, a DTC will be set.