Theory Of Operation

The purpose of the diagnostic is to detect circuit failures on any of the output stages. All output stages are controlled by a current controller that the Transmission Control Module (TCM) can operate in two different modes:

• Current controlled mode (pressure regulators)
• Switched mode or Pulse Width Modulated (PWM) controlled (solenoids)

Solenoid Monitoring:  The TCM measures the actual solenoid voltages and compares them to calibrated thresholds to identify the following electrical failures:

• Short to ground or open circuit
• Short to battery