Possible ECU fault?

[Leeseager]

Hey guys,

my a3 has had a problem for a month now where it when it gets to engine temperature and you turn it off it will not turn back on until it cools down.

So far i've had the cam sensor done twice because it kept coming up on the diagnostic even when codes were cleared, i've also had the timing checked due to lumpy idle. I've found a site called ecutesting.com who can repair ecu's for £250.. I just was wondering if anyone could sort of confirm it sounds like a faulty ecu before i send it off?

 

[mjr901]

Does it crank still? or do literally get nothing? Just a click?

Its more than likely the starter motor. There are endless hot start problems with them. (diesels)

What are the details of the car?

 

[Marshy]

Have you had the crankshaft sensor replaced yet?

 

[Leeseager]

Does it crank still? or do literally get nothing? Just a click?

Its more than likely the starter motor. There are endless hot start problems with them. (diesels)

What are the details of the car?

It's a 2.0 fsi petrol.
it has sometimes started when warm, which leads me to think it is the ecu.

 

[Leeseager]

Have you had the crankshaft sensor replaced yet?

i haven't mate, it went to an audi specialist and they didn't say anything about that i would hope they knew if it would be. I just want to know what it is man but costs a fortune

 

[Marshy]

As I said in your previous thread 99% sure it's the crankshaft sensor. The symptoms your describe sums it up.
you should know by now dealers and some specialists aren't interested if there's no trouble codes.
this is far more likely than an ecu fault, in the trade we've sent ecu's away for testing and a lot of places will say they've got a problem and it's now fixed but it doesn't cure your original fault.
its up to you but I definitely would not be removing an ecu for testing or repair if there's no other running problems with the car.
its more likely the ecu doesn't know the engines turning because the crank sensor isn't giving a signal when hot.

 

[Leeseager]

As I said in your previous thread 99% sure it's the crankshaft sensor. The symptoms your describe sums it up.
you should know by now dealers and some specialists aren't interested if there's no trouble codes.
this is far more likely than an ecu fault, in the trade we've sent ecu's away for testing and a lot of places will say they've got a problem and it's now fixed but it doesn't cure your original fault.
its up to you but I definitely would not be removing an ecu for testing or repair if there's no other running problems with the car.
its more likely the ecu doesn't know the engines turning because the crank sensor isn't giving a signal when hot.

Could you explain why it would be the crank sensor? I don't know too much about cars and especially the electrical side.

 

[Marshy]

When you try and start the car the ecu looks for a signal from the crankshaft sensor then the camshaft sensor this tells the ecu what position the engine is in and when to spark and inject fuel etc.
when these sensors fail the resistance value changes and when the engine is hot the signal from the sensor isn't transmitted to the ecu properly so the car will not start as it either doesn't know the engines turning or the signal is so weak or distorted it can't read it.
once the temperature reduces the sensor will function again.
the ecu looks for the signal to start but once running it doesn't rely on it, hence the reason it will run all day until the cars turned off again.
hope that helps but that's the 1st thing I'd of tried.
if your going to change it use a genuine sensor only

 

[Leeseager]

When you try and start the car the ecu looks for a signal from the crankshaft sensor then the camshaft sensor this tells the ecu what position the engine is in and when to spark and inject fuel etc.
when these sensors fail the resistance value changes and when the engine is hot the signal from the sensor isn't transmitted to the ecu properly so the car will not start as it either doesn't know the engines turning or the signal is so weak or distorted it can't read it.
once the temperature reduces the sensor will function again.
the ecu looks for the signal to start but once running it doesn't rely on it, hence the reason it will run all day until the cars turned off again.
hope that helps but that's the 1st thing I'd of tried.
if your going to change it use a genuine sensor only

okay, that does seem logical to do that. Thanks for explaining. I've asked if this can be changed now dude. If this fails to be the problem would you then say it's the ecu?

 

[Marshy]

I'd take one step at a time but I'm confident that will fix it.

 

[Leeseager]

Thanks, i hope this will fix it. Been without my car for 6 weeks!

 

[Marshy]

Did you get anywhere with this mate?

 

[Leeseager]

Had the part ordered dude, just waiting for them to fit it! I'll let you know though

 

[Leeseager]

It didn't work

 

[Marshy]

Is it exactly the same?
What error code are you getting?

 

[Leeseager]

Yes.

i don't have vagcom or anything but when it got tested or came up with cam sensor which has been done twice.