ECU fails on a 2012 Mercedes C200. Has the dealership sold a faulty car?
The ECU unit on my 2012 Mercedes C200, which has done about 17,000km, has failed. The authorised service centre is offering to replace the unit under warranty, but I’m wondering if they have sold me a faulty piece. Should I accept the replacement?
Rahul B, Mumbai
AAA ECU failures are extremely rare in Mercedes cars, or any modern cars, for that matter. If the company took the initiative to replace the unit, it means the issue was beyond repair. A short in the main wiring harness is one reason that can lead to ECU failure, so in case it happens again, you should insist on having the entire wiring harness replaced along with the ECU.
Also, it is not possible to diagnose a potential ECU failure in advance, so it is probably just a one-off issue and not a deliberate attempt on the part of the dealer to sell you a lemon. We suggest you accept the replacement and insist that the car be thoroughly checked, especially the wiring.