Working through elec system. I have power at ECU plug through 4 red feed wires. But have orange alternator warning on dip and Delphi cannot communicate with ECU. Thinking it was ECU problem, I sent it of to Alliance for testing. Came back with a ‘micro fault’ which they cannot fix. Quoted 1.8K to fix by sending to Bosch - no thanks! So had it back. In the meantime borrowed another ECU from a mechanic. Plugged in but could not communicate. Then noticed the main lower plug into ecu. The clamping arm was closed against the body of the plug, however the locking slider was about 1/4 inch out from the body of the plug. managed to push the slider tight against the body and we then had communication. Swapped back to my original ECU and hey presto off we went! Not sure what the ‘micro fault’ is but the engine appears to be running ok!