Look for the output pin controlling the relay (often A3 ). With the key ON, this pin should show 0V (ground) for 2 seconds, then float open. During cranking, it should ground constantly.
Verify continuity between ECU pin A2 and battery negative. Resistance should be <1 Ohm. bosch ecu wiring diagram
The Bosch Engine Control Unit (ECU)—often referred to as the DME, Motronic, or EDC (depending on the application)—is the brain of your vehicle. It processes data from dozens of sensors to precisely control fuel injection, ignition timing, boost pressure (for turbo engines), and emission systems. But the ECU cannot function without its nervous system: the wiring harness. Look for the output pin controlling the relay (often A3 )