Typically a shielded 2-pin or 3-pin variable reluctance (VR) or Hall-effect signal. Crucial for establishing engine speed and TDC (Top Dead Center).
Pinouts vary significantly between versions. Always verify your specific ECU part number.
Found on older OBD-I and early OBD-II modules for serial diagnostics. bosch motronic ecu pinout
A dedicated, isolated ground circuit strictly for shielding analog sensors from electrical noise.
: Cross-reference the pin number with your vehicle-specific wiring schematic, as wire insulation color codes change depending on whether the chassis is BMW, Audi, Volvo, or Porsche. Typically a shielded 2-pin or 3-pin variable reluctance
. Because this system has evolved over decades—from early 25-pin units in the 1980s to complex 88-way connectors in later models—the "pinout" varies significantly depending on the specific version and the vehicle manufacturer. Common Bosch Motronic Generations
| Pin | Type | Description/Function | | :--- | :--- | :--- | | 1 | A | Fuel pump relay control | | 2 | A | Idle speed control valve - close winding control | | 3 | A | Cylinder 5 fuel injection valve control | | 4 | A | Cylinder 6 fuel injection valve control | | 5 | A | Cylinder 4 fuel injection valve control | | 6 | M | Ground for fuel injection valve output stages | | 7 | A | Camshaft actuator (VANOS) control | | 8 | A | "Check engine" indicator control | | 16 | E | Crankshaft position/RPM sensor signal (+) | | 17 | E | Camshaft position sensor | | 26 | E | Battery voltage (B+) | | 27 | A | Engine control module relay control | | 28 | M | Ground for electronics and shielding of sensors | | 29 | A | Idle speed control valve - opening winding control | | 31 | A | Cylinder 3 fuel injection valve control | | 32 | A | Cylinder 2 fuel injection valve control | Always verify your specific ECU part number
If the ECU is functioning correctly, it will draw roughly of current when the ignition switch is flipped on. A draw of 0mA indicates an open circuit or blown internal diode; a draw exceeding 1.0A indicates a catastrophic short circuit.
: Uses a 35-pin or 55-pin connector. Key pins include Pin 1 (Ignition coil output), Pin 18 (Power input from relay), and Pin 19 (Ground). Motronic M2.9 (VW VR6)
AC Voltage fluctuation (VR sensor) or 0-5V digital pulse (Hall sensor) during cranking 5V Reference Pin Exactly 4.95V – 5.05V with key on Fuel Pump Does Not Prime Fuel Pump Relay Trigger Pin Pin should switch to Ground for 2 seconds at key-on