TCM Coding & Programming: Coding

Coding will assign the control unit to a particular application. Information such as differential ratio, tire size, vehicle series, engine, engine control system, with or without A/C etc., are some of the possible variants that have to be considered. Transmission control units are coded using various methods:

• Grounding pins in wiring harness connector - On early models equipped with the 4HP22/24 EH transmissions, the TCM was coded to the vehicle by means of grounding pins in the wiring harness connector for the TCM. By selectively grounding specific pins in the harness, the TCM was assigned to that vehicle. For example, TCM could be installed in a 535, 635, or a 735. This only applies to the early 7-series (E23, E24, E28).
• TCM ordered for specific application - On some later models, the TCM was ordered for a specific vehicle application, coding was not necessary.
• Coding performed during programming - On systems that use a flash programmable TCM, the coding process is done during flash programming. See Figure .