Apparent PCM failure while in garage

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We took our 2012 Ford Focus C Max in for its routine service on 3rd Jan. We had no problems with functionality before. We were advised that they found an oil leak. Although we had seen no visual sign of oil leak we agreed to get it fixed as they showed us video evidence. First of all they said it was the manifold then they said it was the rocker cover gasket so they had to strip the engine down. This took them several days. After several days we were advised that they had fixed the leak but the car wouldn't start. After another week we were advised that they had found out it was an internal PCM failure but they say that this is nothing to do with anything they have done to the vehicle and is chargeable to us. Please can people advise - what could have caused the PCM to fail? Is there anything that the garage could have done during service, repair, stripping engine down or investigation which could have led to PCM failure? The garage is adamant nothing they have done could possibly have led to the PCM failure but this doesn't sound right to us. It worked fine before, after they have had it for 2 weeks and worked on it extensively, it doesn't! We would be really grateful for people' s views and avice.

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4 hours ago, FedupCmaxowner said:

what could have caused the PCM to fail?

ECUs (aka by Ford, PCM) are very robust and reliable units. They are designed to withstand a lot of abuse, and rarely just fail randomly. Usually there is a cause.

Static electricity (ESD it is called) is one possibility, that can happen when re-connecting connectors, if the operator has not taken some precautions to avoid ESD. Short circuits due to damaged wiring, damaged connectors, or mis-inserted connectors is another possibility.

ECUs are nominally designed to withstand reverse voltage and voltage spikes due to jump starting, but damage has been known to happen this way, if batteries are connected the wrong way round or 24v is used.

I guess the ECU has been powered down for 2 weeks, with the battery disconnected. There is no known reason why this should damage the ECU, but it is possible that it, or another module, has forgotten or corrupted its PATS (immobiliser) codes. If so it should be clear from error codes what has happened, and it should not be difficult for a dealer level garage to re-programme it.

Regarding the oil leak, there are definite guidelines in the MoT manual as to what constitutes an oil leak that would cause a fail. If you had noticed no oil under the car, and no oil loss, then it would be unlikely to be an MoT fail. There have been a lot of reports about garages cashing in on this to deal with insignificant leaks. The MoT manual can be freely downloaded from the government website.

Oh, I have just noticed, how on earth can they claim they have fixed the leak if they can not start the engine! That sounds very, very fishy to me.

If the garage can not be trusted, then you will have to get the car back, find out what error codes are coming up, and find someone more trustworthy to find out what went wrong. There is a small possibility that evidence of bad practice will show up, but to be honest this is unlikely unless they have done something really bad & obvious. It is very sad when a job goes wrong like this. Just allowing the garage to bill you another £1000 or so to replace the ECU would require a lot of trust in that garage though.

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Thank you so much for taking the time to reply, this is really helpful. We don't want to name the garage at this stage as we  are trying to be fair with them but it is a dealer level garage so we are very disappointed that this has happened and they do not appear to be dealing with it correctly. Thanks again

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