1, 2 and 3 Digit Codes: 12

Name of Code: 12-Battery was Disconnected (Info Only)

When Monitored: Whenever the key is in the Run/Start position.

Set Condition: This code is set whenever Transmission Control Module (TCM) is disconnected from battery power (B+) or ground. It will also be set during the DRB Quick Battery Disconnect procedure. On some 95 MY vehicles, it will be set during a DRB Quick Learn procedure.

Theory of Operation: A battery backed RAM (Random Access Memory) is used to maintain some learned values. When the battery B(+) is disconnected, the memory is lost. When the B(+) is restored, this memory loss is detected by the TCM. The code is set and the learned values are initialized to known constants or previously learned values from EEPROM (Electronic Erasable Programmable Read Only Memory). This results in the reinitialization of some parameters.

Transmission Effects: Loss of trouble code data. Immediate limp-in mode if power is lost while operating the vehicle. Normal operation is resumed if the power is restored during the same key start.

Possible Causes:
- Battery voltage removed from TCM
- TCM disconnected
- Dead Battery
- Low battery voltage during cranking
- Quick Battery Disconnect by DRBIII or MDS
- Quick Learn by DRBIII for some 95 MY vehicles.
- Bad TCM ground circuit.