Well bring a really typical blond I switched the jumper leads onto the wrong terminals on the battery.Red to black and Visa Versa. I blew up the on board computer.

Hence I blew up the ECU. I really love this car.

Now do I replace only the ECU or do I also have to replace the key module inside the car and a silver piece I don’t know what it is called.

Please help I have managed to find exactly the correct ECU’s with the correct Mercedes part no but do I need to replace the other 2 things.

I really would appreciate an URGENT reply from anyone who knows please.

Thanks Debbie

  • Welcome to Motor Vehicle Maintenance & Repair! Commented Jan 9, 2023 at 0:34
  • If a diyer, did you check every fuse and replace blown ones? The 'smoke test'; observing smoke from connecting jumper cables incorrectly may help point to damaged wiring, burned electronics, etc. Most if not all EFI systems go thru their power on self tests in a recognizable sequence with indicator lights from the instrument panel during startup. If you remember how indicators lit up then turned off, these are clues. The ecu may have a body computer that runs all lights, indicators with OBD II port. If this overwhelms you, find an auto electrical/electronics specialist.
    – F Dryer
    Commented Jan 9, 2023 at 17:42
  • I tried all that but they now say a need the car key part and the immobiliser to make the vehicle go again. Then it must be programmed with a computer. Thanks for the help though.
    – Debbie
    Commented Jan 10, 2023 at 1:38


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