Transmission Control Module Power Relay

Supplies the transmission control module, which holds the relay energised itself and releases it only after the ignition is off and its learned shift adaptations have been written to memory. That self-holding arrangement explains two symptoms that appear unrelated: a relay releasing too early cuts the supply mid-write, so adaptations save incomplete and shift quality degrades slightly each time the car is switched off, while one whose contacts have welded keeps the module powered continuously and flattens the battery over a few days standing. Cheap, a common failure, and worth checking before any transmission fault list is taken at face value — a module short of voltage reports faults in parts that are perfectly healthy.

Also known as: tcm relay, transmission relay, gearbox relay, tcu relay, transmission power relay

Referenced by 14 codes

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Codes involving this component (14)

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