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Possible ecu failure?


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Hi guys, 

so basically my R is in for body repairs after an insurance claim, since the accident the car has been sat in storage at the garage carrying out the work for 4 weeks mainly waiting for authorisation from insurance engineer. Whilst the garage was waiting on the engineer, the battery died and the garage charged the battery and the car started first time. They left the car running for about half an hour to try charge the battery. So the day they made a start on work they tried starting the car but the car battery had died again and wouldn’t start.

The garage replaced the battery but still not starting, they checked the spark plugs, the fuel lines, injectors, and compression in every cylinder and all seemed okay so they are confused, they then tried using easy start and the car would start but then stall itself. 
they then called Volkswagen and they said to try a couple things but still nothing. they then took the ecu out and set it next to a radiator incase it had moisture inside of it but still nothing.

they tried taking the battery off and touching both cables together and leaving it for 15 mins and that surprisingly worked for all of a minute until the car stalled itself.

they tried again tonight and found that if they hold the brake the car won’t start but as you let go of the brake and touch the throttle, the car springs to life. It then revs to about 1500 rpm and will hold itself there, no throttle response at all, but as you touch the brake the revs drop and the car tries to stall itself and is sounding like it is misfiring.

I don’t know if with the battery going dead could’ve fried something in the ecu but that is what the garage is saying, has anyone got any ideas on what to do or had this problem before? 
Any help would be greatly appreciated! 

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Very, very rare an ECU goes wrong. The place fixing it do you know them or is it the place the insurance company said you had to use? From my experience insurance companies get idiots doing repairs.

Definitely worth doing a voltage check then.    Another possibility is that they have disturbed/disconnected an earth lead somewhere, that could also cause weird intermittent problems.

It sounds like it’s cranking normally, it definitely has fuel because I filled up full before the accident Sent from my iPhone using Tapatalk

It was my choice of garage because there was no trusted dealers anywhere near where I’m from, I’ve always put my cars to this garage and they always do a good job. The body work on the car is done, mainly just waiting for the engineer to tell the garage what to do about the starting problem. 

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It might be worth suggesting they do a voltage check with the engine running (mine is usually 13.3 - 14.7V). 

 

If the voltage regulator is malfunctioning and voltage is outside the normal range (either too low or worse still too high) then various control units can malfunction in bizarre ways.   

 

It would also be worth checking what error codes have been recorded as well, that might help indicate where the problem is.

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The garage said that the error codes change every time, one minute it’ll say one thing, the next it will say another and the first code disappears. The garage can’t send the ecu off to get checked without insurance permission and they’ve been waiting for over a week for the insurance to get back to them.


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54 minutes ago, Muzzafuzza1107 said:

The garage said that the error codes change every time, one minute it’ll say one thing, the next it will say another and the first code disappears. The garage can’t send the ecu off to get checked without insurance permission and they’ve been waiting for over a week for the insurance to get back to them.

Definitely worth doing a voltage check then. 

 

Another possibility is that they have disturbed/disconnected an earth lead somewhere, that could also cause weird intermittent problems.

 

I agree with Raiden, there are very, very few reports of actual ECU failures, and it probably isn't a coincidence that your car started having these weird problems after they have been working on it.

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1 hour ago, Muzzafuzza1107 said:

Could the new battery be the problem? Doesn’t it have to be a specific type of battery that goes into it and have a ‘BEM code’ sticker on it?

 

I suppose it is possible that it is the new battery, but the symptoms you describe are very different to what other R owners have experienced from a failing battery.   

 

New batteries don't have to have a 'BEM' code, and even without re-coding they will work fine (but will last longer if properly re-coded with serial number (anything different), capacity and battery technology)

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They tried starting the car this morning, it started for all of 5 seconds and died again, it did that a couple times, and again the codes are different. I have an obd11 and can go and see what codes are stored later tonight, and can maybe post what I find on the thread? It’s obviously going to have the usual faults with a dead battery on (no acc, hand brake etc)


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Given your symptoms I'd be looking for ignition and injection error codes to begin with, and possibly camshaft timing/actuators issues.

 

You could look at the following battery voltages too: when engine stopped and car asleep (no doors open/shut for at least 5 minutes), then try ignition on but engine off, then starter motor cranking before engine starting, and finally with engine running.

 

I just had a thought.  If a VW car is unhappy about the immobiliser chip then the engine will start as usual (ie easily), but cut out after a short period (5-10 seconds IIRC) - but it usually displays an immobiliser error message if that is the problem.

 

  If your car is a keyless entry with push button start/stop, try starting the engine while holding the remote next to the symbol on the steering column (where the ignition switch would be if your car had one).

 

Has your car had an ECU tune or a tuning box fitted ?  If so, which one.

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Given your symptoms I'd be looking for ignition and injection error codes to begin with.
 
You could look at the following battery voltages too: when engine stopped and car asleep (no doors open/shut for at least 5 minutes), then try ignition on but engine off, then starter motor cranking before engine starting, and finally with engine running.
 
I just had a thought.  If a VW car is unhappy about the immobiliser chip then the engine will start as usual (ie easily), but cut out after a short period (5-10 seconds IIRC) - but it usually displays an immobiliser error message if that is the problem.
 
  If your car is a keyless entry with push button start/stop, try starting the engine while holding the remote next to the symbol on the steering column (where the ignition switch would be if your car had one).

The mechanics say they have looked at the injectors and they are fine, they have tried the immobiliser and it’s fine with no errors but even when they try starting, it will crank for a good amount of time before starting and then cut out


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10 minutes ago, Muzzafuzza1107 said:


The mechanics say they have looked at the injectors and they are fine, they have tried the immobiliser and it’s fine with no errors but even when they try starting, it will crank for a good amount of time before starting and then cut out

Does it sound like the starter motor is cranking at a normal speed, or possibly a bit slow ?  If the cranking RPM is too low the ECU usually won't instruct the injectors to inject any fuel.

 

Another possibility - is there even the slightest chance the car is low/out of petrol ?  Sometimes the fuel gauge will indicate there is plenty of fuel but the tank is actually (near) empty.  If there is a problem with the fuel supply/lines/filter you can get an engine that is hard to start and/or cuts out soon after starting.  This one has tripped up quite a few people because they trusted the gauge but fuel wasn't getting through to the injectors (but this should show up as a error code for requested vs actual fuel pressure).

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Does it sound like the starter motor is cranking at a normal speed, or possibly a bit slow ?  If the cranking RPM is too low the ECU usually won't instruct the injectors to inject any fuel.
 
Another possibility - is there even the slightest chance the car is low/out of petrol ?  Sometimes the fuel gauge will indicate there is plenty of fuel but the tank is actually (near) empty.  If there is a problem with the fuel supply/lines/filter you will can get an engine that is hard to start and/or cuts out soon after starting.  This one has tripped up quite a few people because they trusted the faulty gauge.

It sounds like it’s cranking normally, it definitely has fuel because I filled up full before the accident


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Sounds like it is getting towards time to get a fresh set of eyes (and mind) to look at it.  If it was my car I'd want a good (intelligent) VAG expert to troubleshoot, starting from scratch (ie don't assume anything from what the current custodians say they have done/tried/tested). 

 

Even if you have to pay for it yourself it is probably worth it for avoiding further time & inconvenience.  And if the new person discovers that the repairers have stuffed something up I'd be insisting they pay for the new "eyes" (and given the timing I strongly suspect they have). 

 

I wonder if they turned the ignition on with some electrical components removed or unplugged, that caused me a lot of issues when my Octavia was at a crash repairers, and I ended up taking the car back to my VW dealer for some kind of software reset.

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