BMW E32 automatic transmission limp mode
My E32 automatic goes into limp mode, what usually causes it?
Common causes are a wiring harness fault, a speed sensor fault, a worn valve body and an internal gearbox fault, for example a bearing. In limp mode only 4th gear and reverse work. Restarting the engine can clear the mode for a while.
Can low oil or heat cause limp mode?
Yes. Too little oil or a poorly working oil cooler raises the temperature, so the gearbox limits engine power and goes into limp mode. The oil level is checked with the gearbox at no more than 40 degrees, because when hot the reading shows too little.
How can I tell whether the fault is in a sensor or inside the gearbox?
Read the fault code and check the wiring harness and connectors first. If torque makes the gearbox slip and the speed sensors give differing readings, the cause is usually mechanical. If the forward gears are missing, the cause can be a broken clutch pack.
What if the Trans Program message appears and power disappears?
The cause is not always the gearbox itself. The message can be triggered by an engine management fault, such as the mass air flow sensor (MAF), or a stuck throttle where the angle sensor wire is disconnected. Find out the fault code first and check the engine side.