Transmission Hydraulic System
Transmission Mechanical Operation
Faulty Transmission Controller Module (TCM)
Engine Light ON (or Service Engine Soon Warning Light)
This diagnostic checks if the Transmission Controller Module (TCM) is capable of identifying the engaged gear after the initialization is performed at power ON of every trip. The TCM looks at many different parameters including the actuator position sensors to determine what gears (if any) are engaged. If the TCM cannot resolve conflicting information or otherwise determine what gears are engaged then a fault is set.