View Full Version : Does disconnecting the ECU clear fault codes?

04-02-2010, 08:50 PM
Does disconnecting the ECU clear fault codes or do they have a backup battery of some kind?

04-02-2010, 08:55 PM
And the reason you want to do this is why ??

04-02-2010, 09:04 PM

I'm guessing someone's been busy on google and rather than pay a) a garage or b) a supplier of diagnostic equipment for a scanner/lead, they're trying to force a manual reset.

04-02-2010, 09:11 PM
No, the fault memory is non volatile.

04-02-2010, 09:49 PM
My Mk3 1.4 1994 Golf stops after going through a puddle but a wait, or disconnecting the ECU makes it go again.

It stopped like this the other day and I had the ECU completely off the car to inspect and clean the connector pins with electrical contact cleaner, I then bought a diagnostic lead hoping to find some fault codes but found none - and so wondered if they get cleared (or not) if you disconnect the ECU.

Yes, I could have worded my original question better.

I guess I must be doing something wrong with the cable, it's a bit of a learning curve.

05-02-2010, 02:00 PM
I would say you need a new distributor.

05-02-2010, 04:57 PM
My dizzy has one of those grey metal shields around the cap but the car runs fine at all other times?

Is there a way of creating a small fault code so I know that my cable is working???

05-02-2010, 10:49 PM
Read the codes with the engine not running, you should get

00515 Hall sender G40 no signal

or disconnect the coolant temperature sender under the dizzy, you should get

00522 Coolant temperature sender-G62 Open circuit/short to positive

06-02-2010, 01:55 AM
Thanks, I will try the said things.

To return to my cars symptoms after a puddle incident, they are similar to when I had an ignition coil fail, the engine was difficult to start and wouldn't pull the skin off a rice pudding.

So whilst investigating every avenue I'm also thinking about prevention and shielding the coil from water - and wonder if the MK3 had one originally?

Will try for an image on Google, I do like to get to the bottom of things.

06-02-2010, 07:20 PM
The coil on the Golf 3 is very susceptible to even a slight water splash, I had one in just before Christmas with the same issue and a new coil appears to have fixed it. That already had a plastic bag over it but this had not worked. GSF sell coils by Beru which are very good but avoid white box unbranded items, the quality is awful. They never had a water cover.


06-02-2010, 08:01 PM
Thanks Crasher. Now that's the kind of advice I like, gained from experience. I will check out the said coils.

Getting the message.