My Lad's faulty Golf 4 Motion

Rob Gaskin

Rob Gaskin

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Any VW specialists on here?

My lad has the engine management symbol illuminated (like 20% of the country!).

He has a Golf 2.8 and been told the following (cost £70).

Basically there are 2 fault codes that relate to each other.

P1118 - lambda sensor 2 (the one after the cat) of bank 1 of the engine is showing the fault. Apparently the mixture is rich, there is too much fuel and this is causing emissions out of range.

Once he had isolated which sensor it was, he was able to test it by putting a voltage across it. Apparently it'd worked as it should, although this doesn't mean under normal circumstances when it should switch due to hot gases that it actually does work. The sensor is quite corroded. It will cost in the region of £120 for a genuine VW sensor + labour to fit.

However, there is also another fault code:

P1198 - wiring fault, open circuit. This could be the wiring going to the sensor or a circuit within the ECU. He thinks it could be something like a resistor or diode on the circuit board of the ECU. He is led to believe it is the ECU due to the fact that the car runs 'lumpy', especially on start up when it takes about 10 seconds for the revs to find the right level.

He suggests taking the ECU out of the car and sending to a specialist in Manchester who will be able to pin point the exact resistor or diode that is faulty. He said VW would just fit a new ECU and charge me a fortune, this makes me think he is suggesting that an ECU can be fixed. I have asked him to provide me with a quote. I would be without my car for at least a week!

I've done a search on the internet and I haven't been able to find anything relating to those specific fault codes yet but there are loads of posts about emissions warning lights on the vag-com forum.
 
Just to give the Thread a bit more 'feeling' this is his lovely car that is mis-behaving.
 

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Why not replace the ECU with one from a breaker? I'm sure the VW/Golf/4Motion forums will have someone breaking one and a spare ECU for sale. Garages always want to repair the unit or replace it, both will likely cost a lot more than just buying a replacement ECU for it from a breaker.
 
HollowPoint said:
Why not replace the ECU with one from a breaker? I'm sure the VW/Golf/4Motion forums will have someone breaking one and a spare ECU for sale. Garages always want to repair the unit or replace it, both will likely cost a lot more than just buying a replacement ECU for it from a breaker.
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I suggested that to him but he is worried about fitting a secondhand ECU that might not match his car and cause other issues.

I told him to try 24/7 spares who I have used in the past.

Have you ever fitted an ECU off another car?

He is considering changing the Lambda at £120 to either sort it or eliminate it?
 
I'd change the lambda first, then I'd change the ECU for one from another car. Provided he gets one off a 4motion of the same series (MkIV Golf it looks like?), there won't be any issues. I've swapped ECUs from one car to another countless times in the past with no issues.
 
Indeed, as I said in my first post, best place for advice for it, would be either the VW forums, or better yet, specifically the Golf or 4Motion forums. My ex was very heavily into her VWs and one of her friends had a one of the Corrado G60s on a 2000 plate, he changed his ECU without reprogramming his keys, which is why I don't think it'll be required, but Gary could well be right. Tell your lad to get signed up on their owners forums and do some reading, could save him a pretty penny.

Just a thought too, but getting a dealership to re-program the keys is probably an hours labour, which is still cheaper than getting the ECU repaired most likely, lol.
 
I'd replace the sensor first, it sounds like it needs replacing even if it doesn't fix the problem.

If the codes still show after clearing then I'd just replace the ECU rather than attempt to repair, everything inside the ECU is surface mount, meaning tiny tiny components that you need an exceptionally steady hand to remove and replace - if you can even work out which one is faulty in the first place.
 
Thanks guys, all helpful and reassuring stuff. We are not rushing into anything - the car runs well. I love it - I had a VR6 but this is even better.

My Dad has a Toyota Avensis - light been showing for 2 years and it runs really sweetly and passed two MoTs.

I haven't had an engine management light on my 240 yet - in fact not even an ignition light :thumbs:
 
lol :)

Didn't they change the MOT this year regarding warning lights? Not sure how it works now, but certain lights you can't get away with any more.
 
morbias said:
lol :)

Didn't they change the MOT this year regarding warning lights? Not sure how it works now, but certain lights you can't get away with any more.
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Heard differing tales - I think it's ABS, traction control, tyre pressure lights etc that are covered by the MoT.
 
The engine management light (or fault light as it should be called) covers much more than just the engine systems, Audi A3 for example it comes on if there is fault with the brake light switch.

P1198 wiring fault is pretty unspecific and could relate to anything. It is quite likely to be a faulty Lambda that is causing this fault code to produce.

I recently had a faulty Lambda on my (the missus she says) Note, and it also threw out a PATS fault code at the same time, replaced the Lambda and the PATS code cleared.

I would recommend a replacement Lambda in the first instance.
 
Developments!

Well he had decided to do the Lambda first because he's scared of an ECU change and unknown consequences.

This morning he started it early to go to work (shifts) and left it running to get something from the house. When he got back to it the ABS and EPC warning light were illuminated. He decided to switch it off and restart it to see if it cleared itself and NOTHING.

The car shut down, clock reset and it wouldn't even turn over i.e. solenoid not in circuit. He's gone to work in his wife's car. I don't think that there is a battery cable/terminal issue but I've told him to check tonight.

So is this the ECU telling him it's had enough? Perhaps the garage were correct and the Lambda is ok?

So the big question is - is an ECU swop straightforward from one vehicle to another? Hollowpoint you seem to think it's worth a go. I would be tempted too epecially as there is one on ebay for £35, but could it ****** something up and cause more trouble?
 
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Basically if you put the new ECU in and it doesn't start, because the keys need re-programming, you're roughly in the same boat you are now (With a car that doesn't start) If you then pay the £50 (or whatever it is) to get the keys re-programmed (if it's even needed), then you've spent circa £85 and the car might be fixed, or it might not. Without being near the car, having an ECU to hand, being an Avid Golf driver, I can't say for certain.

If I personally, were I in the same boat, I would buy the £35 ECU and find out from the 4motion forums I linked to earlier in the thread, whether or not it needs to have the keys done when the ECU is swapped. If it does, I'd just get it to the dealership and have them re-program the keys with the new ECU in, if not, I'd obviously just swap it. I reckon for less than £100 (Provided the VW garage do just charge an hours labour like Ford/Toyota/Various other garages do) it's gotta be worth a go.

Swapping the ECU, provided it's a good one, will not cause more faults. The only potential issues with replacing ECUs are basically:

1. Newer cars may require the keys re-programmed
2. If the new ECU is duff it won't prove anything
3. If the new ECU has been re-mapped badly, it could over/under fuel obviously

I'd confirm that ECU on ebay hasn't been re-mapped and is as stock, then just buy it and whack it in the car tbh, lol.
 
It sounds like the ECU has reset itself and the immobilizer isn't recognising the key any more :(

It does seem like the ECU could be fried, but perhaps it can be successfully re-programmed. I'd check the wiring and connectors going to the ECU first, maybe there is a short somewhere (the ECU memory shouldn't just wipe itself). Wouldn't want to put in a replacement and have the same thing happen.
 
Thanks guys.

Morbias Lee's mate (a Peugeot trainer) seems to think it might be an electrical fault too e.g. wiring or damp in fuse box etc.

Also one of the ECU sellers on ebay had confirmed that it would need reprogramming re immobiliser.
 
Seems like this morning's problems were a bum-steer.

I've found out that when he left it ticking over he had lots switched on (including heated seat :eek:) so it drained the battery and brought up some lights. When he switched it off to reset them the car wouldn't start because the battery was discharged. Because of the recent issues put 2 and 2 together and got 5!

I need to educate him about these things ;)

It started ok with 'jump leads' this evening (after work).

So just left with the original fault - I hope!
 
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