How to reset ECU on VW Golf Mrk3?

cara_essex · 8 Dec 2007

Hi,

Please could someone tell me if its possible to reset the ECU on a golf mrk3 (1998) just by disconnecting the battery for a while, or if i need to rest it by computer?

thanks

^neo^ · 8 Dec 2007

Disconnect battery for half an hour will set it back into learn mode. Not 100% sure if it clears all fault codes too though (pretty sure it does)

cara_essex · 9 Dec 2007

Thanks neo, although being a woman and pretty daft with cars -

how do I go about disconnecting battery without frazzling myself??!

Sorry for stupid question but would rather be safe than sorry!!

Thanks

Stivino · 9 Dec 2007

Arm yourself with a 10mm spanner and remove the earth lead from the battery.

InTheBeginning2007 · 13 Dec 2007

Firstly tell us why you want to do this. i.e what is wrong with the car. And no, it will not get rid of fault codes. You actually have to fix the fault to do that.

^neo^ · 13 Dec 2007

InTheBeginning2007 said:
And no, it will not get rid of fault codes. You actually have to fix the fault to do that.

You sure about that

LeeJC · 14 Dec 2007

I always disconnect both battery leads, black first then red.
Short the leads together (while off battery with a short bit of 2.5mm cable and turn the lights on, and it does cure the ECU Faults, along with the airbag computer faults, light faults, locking faults, heating faults etc etc etc.
These 7's have far too many computers on them.

For "Cure" see CLEAR, faults still in the system will be re flagged on next occurance.

InTheBeginning2007 · 14 Dec 2007

LeeJC said:
I always disconnect both battery leads, black first then red.
Short the leads together (while off battery with a short bit of 2.5mm cable and turn the lights on, and it does cure the ECU Faults, along with the airbag computer faults, light faults, locking faults, heating faults etc etc etc.
These 7's have far too many computers on them.

I am just curious, but how often do you do this procedure?

LeeJC · 14 Dec 2007

I've done it twice, once after i replaced the fuel tank breather that was firing up a non displayed fault code.
And once after changing the wheels to reset the gearbox ECU.
Oh and that's in 18 months.

And i should correct my post really, it doesn't cure any faults at all, unless you replace the bits that are faulty, what i meant was it will CLEAR the stored faults until next occurance.

InTheBeginning2007 · 14 Dec 2007

LeeJC said:
And i should correct my post really, it doesn't cure any faults at all, unless you replace the bits that are faulty, what i meant was it will CLEAR the stored faults until next occurance.

That was my point originally. It is better to fix the actual fault. I have worked on many VAG (admitidly not your model golf) cars and the fault codes are not cleared when the battery is removed. You need to connect it to a computer to clear them. Maybe that model is an exception. Also, is your car automatic or manual gearbox. If it is a manual, then there will be no gearbox ECU and if it is an auto, the ECU will not care or know if you have changed the wheels (unless you put a bigger wheel on the left of the car than on the right, in which case the ABS might complain).

Currently I am working on a new model Audi A8. That is a nightmare. 49 computers in the car! If you disconnect the battery it does not clear fault codes. It generates several hundred more.

How to reset ECU on VW Golf Mrk3?

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