These early systems used a 35-pin (sometimes 55-pin on later M1.3) rectangular connector. They controlled batch-fire injection (injectors fire in groups) and single-coil ignition with a distributor.
Key Pinout Details (M1.3 35-pin – e.g., BMW E30 325i):
Note: M1.0 and M1.1 often lack oxygen sensor inputs (open-loop only).
The main view is a schematic representation of the ECU plug.
You cannot guess. Using the wrong pinout can fry an ECU or sensor. Follow these steps:
Most early Motronic systems use a 35-pin rectangular connector (often found on M1.0–M1.3) or a 55-pin square connector (M1.7 and later).
Below is a generalized reference for a typical 35-pin Motronic (M1.3) — common on late 80s/early 90s BMW 3-series (E30) and 5-series (E34).