Broken ecu by changing a crank pos sensor?

AhhBisto

AhhBisto

AhhBisto

Associate
Joined
23 Feb 2019
Posts
461
Got a 08 Focus in workshop due to an intermittent fault of it cutting out past 70mph+, it was running when in. Unfortunately after a crank sensor was replaced (showed as faulty in diagnostics) the car would no longer turn over and even old sensor failed.

It was replaced but now the car no longer works. Everything has been checked and came out perfect other then ecu. Is it possible ECU could have failed during a simple sensor change?
 
When you say the engine no longer turns over, do you mean it is completely dead and nothing happens when you turn the key. Or that the engine turns over but no longer fires up?

What engine is it?
 
Garages sometimes diagnose a faulty ECU, they are nearly always wrong. They also often see "something something crank sensor" in the diagnostics and replace the sensor without a second thought or even a brief glance at the diagnosis instructions in the workshop manual for the part.

If the crank sensor was faulty the engine wouldn't run, this is actually consistent with your description in the OP. Perhaps they did confirm the wiring harness and connectors were all ok then they replaced the part.

Now it "doesn't hold revs", so the ECU is faulty. Not enough information here are all, you've paid for it so ask them for the diagnosis before agreeing to splurge on an ECU.

This is entirely speculation on my part but I think they don't have a clue what is wrong & the ECU is reporting no codes, so they just point at the magic computer box they don't understand.
 
BigglesPiP said:
Garages sometimes diagnose a faulty ECU, they are nearly always wrong. They also often see "something something crank sensor" in the diagnostics and replace the sensor without a second thought or even a brief glance at the diagnosis instructions in the workshop manual for the part.

If the crank sensor was faulty the engine wouldn't run, this is actually consistent with your description in the OP. Perhaps they did confirm the wiring harness and connectors were all ok then they replaced the part.

Now it "doesn't hold revs", so the ECU is faulty. Not enough information here are all, you've paid for it so ask them for the diagnosis before agreeing to splurge on an ECU.

This is entirely speculation on my part but I think they don't have a clue what is wrong & the ECU is reporting no codes, so they just point at the magic computer box they don't understand.
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Got to say that is my experience nowadays, they aren't mechanics any more, rather parts fitters.

Had an issue with an Audi once, garages couldn't diagnose the issue, amongst the faults were hazards coming on at random (whilst driving, whilst parked up and locked etc), took it to an auto electrician who just ordered a replacement hazard light switch ( at a cost of £28) which didn't fix the issue and they refused to send the part back, so I had to pay for a part which hadn't fixed the issue because they couldn't diagnose it properly.

The actual fault turned out to be water getting in to one of the ECU connectors due to a previous mechanic catching the rubber seal and it had rolled up slightly inside the connector.


There is an auto electrician local to me that REALLY knows his stuff, he is no good though, he is renowned around all of the local garages, he is a bit eccentric, very very disorganised, constantly late, likes to be thorough to the point his work is just slow. and frequently doesn't turn up to a booked appointment etc.
 
Ford tech came out today to garage and I'm guessing flashed the ecu and it's working great now got to drive it home at last.

I'm guessing someone may have done a cheap map on it before I owned it but will never know the real reason.

Sometimes turning it off and on again is the only solution :D
 
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