System Power Supply

On Board Monitoring

The TCM monitors all input and outputs to identify possible failures. If a fault is detected the TCM takes the appropriate action to ensure the transmission enters a safe mode of operation, without sacrificing transmission durability or driver safety.

This section only contains those monitors that will cause the Malfunction Indicator Lamp (MIL) to illuminate.

System Power Supply

Battery voltage
Battery voltage is continuously monitored whilst the engine speed is greater than the threshold speed. The diagnostic monitors the TCM supply voltage for voltages greater than, or less than fixed thresholds. If the engine speed is low, but battery voltage is high, a jump-start condition (batteries in series) has been detected, and the diagnostic will not flag.

The monitor starts by checking for the jump-start condition. The battery voltage is checked against its high threshold of 16v whilst the ISS sensor is checked to see if it is below it s low threshold of 1000 RPM (indicating engine speed). If both conditions are true then a jump-start condition is identified, the transmission temporarily put into limp home and the battery voltage monitor is deactivated. When either the jump-start timer times out or the monitored conditions change to within the required thresholds, the limp home is deactivated and the monitor restarted.

If a jump-start condition is not identified, the engine speed is above its minimum threshold and the transmission is not in limp home because of another code then the battery voltage check continues. The voltage is checked against both upper and lower limits. If either is exceeded a Diagnostic Trouble Code (DTC) is logged.

Pressure Regulator and Solenoid Power Supply
The pressure regulator and solenoid supply is the power supply from the TCM that supplies the shift solenoid, pressure regulators and the TCC solenoid. The supply is monitored when any of the solenoids are activated. The TCM will detect a fault condition if the supply voltage either exceed its upper threshold or falls below the lower threshold. If either condition exists, DTC P0651 will be logged.

Sensor Supply
The sensor supply is the power supply from the TCM that supplies the two speed sensors and the gear selector hall effect switches. The sensor supply is continuously monitored whilst the ignition is on. The TCM will detect a fault condition if the supply voltage either exceed its upper threshold or falls below the lower threshold. If either condition exist, DTC P0641 will be logged.