Repair and Diagnosis: Electrical: Starter: Starters: Operation

On 7-series and 540i with automatic transmission, starter is controlled by Digital Motor Electronic (DME) control module. After the DME control unit receives the input signals from the ignition switch and neutral safety switch, it energizes the starter relay, which in turn energizes terminal No. 50 at the starter motor. After the DME control unit receives a signal from the crankshaft position sensor that the engine is running (920 RPM cold; 680 RPM at normal operating temperature), the DME control unit switches off the starter relay.

On all other models, starter is controlled by electronic immobilizer control unit. Turning ignition switch to START position energizes terminal No. 3 at electronic immobilizer control unit. When clutch is depressed (M/T) or gear selector is in Park or Neutral (A/T), a signal is sent to terminal No. 9 at electronic immobilizer control unit. When both these signals are received by electronic immobilizer control unit, terminal No. 50 is energized at starter motor.