Automotive technicians, ECU tuners, and DIY engine swappers.
If you are looking at a bare ECU or harness, identifying pins requires careful observation: bosch motronic ecu pinout
1991 BMW 318is (Motronic M1.3, 55-pin) Symptom: Cranks but no start. Fuel pump does not prime. Automotive technicians, ECU tuners, and DIY engine swappers