Theory Of Operation

The purpose of the diagnostic is to detect circuit failures on the solenoid driver circuits. The 948TE Transmission Control Module (TCM) solenoid driver circuits are low side drivers. This means that the solenoids are supplied power through a fused B+ circuit in the TCM and the ground side is Pulse Width Modulated (PWM) by the TCM to control solenoid operation. By modifying the PWM signal the solenoids can operate as either on off hydraulic valves or as variable pressure control valves. This valve body uses both depending on individual solenoid function in the hydraulic system.

Solenoid Monitoring:  The Application-Specific Integrated Circuit (ASIC) in the TCM indicates the following circuit failures via the TCM Central Processing Unit (CPU) :

• Short to ground.
• Short to battery.
• Open circuit.