Always double-check pinouts against multiple sources, build a proper breakout box if you do frequent diagnostics, and respect the sensitive analog signals that kept these engines running famously for decades.
The ECU driver transistor may be shorted to ground, or a wire is shorted. Disconnect ECU; if pump stops, check ECU output pin. 3. No Spark or Injector Pulse Symptom: Cranks but no start. Have fuel pressure but no spark.
For mechanics, tuners, and DIY enthusiasts, understanding the is not just a technical exercise—it’s a survival skill. Whether you are chasing a no-start condition, wiring a standalone ECU, or retrofitting an older engine into a new chassis, the pinout diagram is your roadmap. bosch motronic ecu pinout
| Pin | Function | Notes | |------|-------------------------------|-----------------------------------| | 1 | Injector cylinder #1 | Ground-switched by ECU | | 2 | Injector cylinder #2 | | | 3 | Injector cylinder #3 | | | 4 | Injector cylinder #4 | | | 5 | Injector cylinder #5 | (6-cyl engines use pins 5 & 16) | | 6 | Injector cylinder #6 | | | 7 | Main relay control | ECU grounds to activate | | 8 | Fuel pump relay control | | | 9 | Idle control valve (ICV) | Duty cycle signal | | 10 | Speed output (to cluster) | Sometimes TTL signal | | 11 | Diagnostic request (pin 15 of DLC) | | | 12 | Check engine light | Ground to illuminate | | 13 | Power ground | To engine block | | 14 | Signal ground | For sensors | | 15 | +12V battery constant (pin 30) | Keep-alive for adaptation | | 16 | +12V ignition switched (pin 15) | Main ECU power | | 17 | Crankshaft position sensor (signal) | VR sensor (AC voltage) | | 18 | Crankshaft sensor (shield/ground) | | | 19 | Crankshaft sensor (negative) | | | 24 | Throttle position sensor (wiper) | 0.5V – 4.5V | | 25 | TPS reference voltage (5V) | | | 26 | TPS ground | | | 27 | Coolant temp sensor | Voltage divider output | | 28 | Intake air temp sensor | | | 44 | Oxygen sensor signal | 0.1V – 0.9V | | 52 | Ignition output #1 | To ignition coil/transistor |
The Bosch Motronic system is one of the most iconic and long-running engine management systems in automotive history. From the legendary BMW M20 and M50 engines to vintage Porsche 944s, Audi Quattros, and early Volvo turbos, Motronic bridged the gap between purely mechanical fuel injection and fully modern digital engine control. and early Volvo turbos
Note: Not all pins listed – full diagrams available from factory repair manuals (e.g., BMW ETM). Application: Early 1990s VW/Audi (Corrado G60, 2.0 16V), Saab 9000, Fiat.
Locate fuel pump relay control pin (e.g., M1.3 pin 8). Should be 12V with key on? No – Motronic grounds this pin only during cranking or when RPM>10. and DIY enthusiasts
35-pin rectangular (1.1) or 55-pin (1.3). The 55-pin is sometimes labeled “M1.3”.