3.1 Transmission Control Module
3.1 Transmission Control Module3.1.1 Description
The TCM performs the following self-test integrity diagnostics on its internal hardware and software to check for faults, a fault is detected if:
1. The battery supply voltage to the TCM drops below 9 volts for longer than a predefined time, whilst both the engine and turbine shaft are rotating at greater then 1400 rpm.
2. The battery supply voltage to the TCM exceeds 16 volts for longer then a predefined time.
3. The TCM processor identifies one of the following failures
^ A error accessing the RAM
^ A lock up of the processor
^ Analogue to digital conversion errors
^ Analogue to digital conversion errors as a result of overheating
4. The internal TCM chip temperature exceeds a variable temperature threshold depending battery supply voltage. The TCM is situated within the transmission on the valve body. As the TCM controls a number of high power solenoids and is surrounded by transmission fluid it can get very hot. If the temperature of the hardware rises above a pre-determined level, the TCM will be shut down. Prior to the TCM shutting down it will log a fault code, during shutdown the transmission will enter mechanical limp-home mode. A temperature dependent resistor mounted on the processor performs monitoring of the chip temperature.
5. The voltage output from the TCM chip temperature sensor is greater than 4.95 volts.
6. The voltage output from the TCM chip temperature sensor drops below 0.1 volt.
7. The sensor supply voltage output from the TCM is greater than 8.0 volts.
8. The sensor supply voltage output from the TCM drops below 6.42 volts.
9. The calculated checksum performed on the FLASH EEPROM does not match the stored value.
10. The FLASH EEPROM has exceeded its emulated lifetime.
11. The supply from the TCM to the pressure regulators and shift solenoid cannot be maintained at the correct level. A field effect transistor (FET) is used to control the power supply to the pressure regulators and shift solenoid, this group of checks monitors both the transistor operation and the resulting output voltage to the solenoids for correct operation. Five DTC's are used to identify the exact nature of the failure.
12. Two or more faults exist on related speed sensor inputs to the TCM. In this instance, the TCM is unable to generate a substitute values for either of the signals and so can no longer adequately control the transmission system.
Transmission Control Module
If the above table does not include details of the following enabling conditions: - Intake Air Temperature (IAT), Engine Coolant Temperature (ECT), vehicle speed range, and time after engine start-up then the state of these parameters has no influence upon the execution of the monitor.
Ref. 1: TCM Chip temperature versus battery voltage