For more information on the Bosch Motronic ECU pinout, we recommend the following resources:
Late 1990s Audi A4/S4 (1.8T 058 block), Passat, early VW Golf 4.
Delivers a 0-1V or wideband signal measuring exhaust oxygen content. Actuator Outputs bosch motronic ecu pinout
The table below provides a general layout for a 55-pin Bosch Motronic system, used by Audi for example on its 2.2L turbo 3B engine.
Power and ground connections are the foundation. A (often on pin 18) maintains the ECU's memory (e.g., stored fault codes and learned fuel trims) even when the ignition is off. A switched ignition supply (often on pin 27) activates the ECU when you turn the key. Multiple dedicated ground pins (e.g., pin 10, 14, 19, 24) ensure a clean, noise-free electrical path for different circuits. Battery voltage (B+) (e.g., pin 18) supplies constant power. For more information on the Bosch Motronic ECU
Early 1990s VW/Audi (Corrado G60, 2.0 16V), Saab 9000, Fiat.
These versions are often directly swappable. The 1.3 version typically uses a single board inside the casing, whereas the 1.1 uses two boards. Power and ground connections are the foundation
: Numbers are typically embossed directly on the plastic ECU connector or the harness plug. For example, pins 1, 15, and 30 often correspond to standard DIN terminal designations (Ignition Coil, Switched 12V, and Constant Battery Power, respectively). 2. Common Pinout Assignments (55-Pin Motronic 1.x) Pinout | Bosch Motronic Ecu
Before looking at pins, understand the system. Motronic was revolutionary because it combined and ignition control (Electronic) into a single ECU. Unlike older systems that used separate boxes for fuel and spark, Motronic synchronizes both.
Late 1980s to early 1990s (BMW E30 325i, E34 535i, Porsche 944 S2, early Volvo 940 Turbo).
Heavy-gauge wires bolted directly to the engine block or chassis to ground high-current drivers (injectors, coils). II. Critical Input Sensors (Engine Vital Signs)