Component Tests and General Diagnostics

Checking the power supply and ground terminals

Checking the power supply and ground terminals

Power supply to the transmission control module (TCM)
The transmission control module (TCM) is powered via two power inputs on the control module.
When the ignition is on, the two power inputs are powered and the transmission control module (TCM) is in active mode.
1. Power input 1, terminal #A11(#A41), is supplied with power via a fuse from the start control module (SCU), ignition position II (KL15, "wake up"). This power input is used to activate the engine control module (ECM). When the power input is supplied with power, the system relay will be activated and power input 2 will be supplied with power. The transmission control module (TCM) will not be activated if there is an open-circuit
2. Power input 2, terminal #A1(#A31), is supplied with power via a fuse from the system relay. The system relay is activated by the engine control module (ECM). This power input governs the supply of power to the transmission control module (TCM). The transmission control module (TCM) will not be activated if there is an open-circuit.

Checking the power supply
Check the power supply cable from the start control module (SCU) to transmission control module (TCM) terminal #A11(#A41). Check for an open-circuit. Check for loose connections. Check for contact resistance. Check for oxidation. Check the fuse. The voltage must be approximately battery voltage when the ignition is on.
Check the power supply cable the system relay to transmission control module (TCM) terminal #A1(#A31). Check for an open-circuit. Check for loose connections. Check for contact resistance. Check for oxidation. Check the fuse. The voltage must be approximately battery voltage when the ignition is on.

Ground terminal, transmission control module (TCM)
The transmission control module (TCM) has a ground input. See the relevant wiring diagram for further information about ground terminals.
1. The ground input terminal #A9 (#A39) is power ground and is connected to the ground terminal in the car body.

Checking the ground terminal
Check the ground lead between the transmission control module (TCM) and the ground terminal #A9 (#A39). Check for an open-circuit. Check for loose connections. Check for contact resistance. Check for oxidation. With the ignition on, the drop in voltage between the ground connection for the transmission control module (TCM) and the ground terminal must not be greater than 0.5 V.
Remedy as necessary.

Other information
- Connecting the breakout box, AW55-50/51SN Connecting Breakout Box, Transmission Control Module (TCM)
- Signal specification, AW55-50/51SN Signal Specification, Transmission Control Module (TCM)
- See the relevant wiring diagram for information about circuit and ground terminals in the bodywork
- Checking wiring and terminals Checking Wiring And Terminals





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