Audi A3 engine management light issue help needed

wookie66

I own an X reg 1.8 petrol Audi A3 which has 90k miles and has served me well since I purchased it some six years ago

Recently the Engine Management System (EMS) light came on so got it diagnosed at local garage which indicated error codes as a front oxygen sensor and temp sensor error

So purchased original replacement parts from the Audi Stealer and got these two bits fitted (£250 incl fitting)

Within 200 miles the EMS light came on again

Took it back to the garage they hooked it up to the diagnostic software and two error codes appeared

One code indicated front oxygen sensor needs replacing since burning too lean.......but I just had it replaced with an original part

Second spurious code mentioned something like altitude reading outside of normal parameters or similar which baffled me and the garage despite googling this which came up with little useful info

They reset the EMS light and rechecked the oxygen sensor which was fine and again within 100 miles the EMS light came on yet again!

Hooked it up again to the EMS and same error codes reappeared!!

Would anyone with knowledge of Audis have any idea whats going on?

The car runs perfectly, no juddering, even when idle and ticks over without any problems. Even on the motorway haven't noticed anything irregular in performance

Miles per gallon is pretty average given its an auto and I haven't noticed any difference in it using more fuel than usual

Any ideas thoughts welcome

Audi main dealer have quoted min 1hr labour to investigate at £150!

And that is just the labour - but they do have the VAG COM software which may be able to pinpoint the problem but I am loathed to go them since I know it will burn a massive hole in my pocket

I live in West London nr Heathrow and would appreciate any recommended independent Audi garages in my area

Any assistance is appreciated on this annoying issue

GolfBravo

Oxygen sensor detecting a lean condition (too much oxygen)? Or a faulty oxygen sensor? Can you get the error codes?

Lean condition could indicate a faulty/dirty MAF.

wookie66

Error code is P0420 and detecting lean condition

GolfBravo

P0420 catalyst system efficiency below threshold?

And detecting lean condition?

Front oxygen sensor error (lean condition) would indicate faulty/dirty MAF sensor or air leak between the sensor and intake manifold, or a vacuum leak.

Start with the cheapest/free things first.
1. Disconnect the battery for 15 minutes and then reconnect. Is the light gone? Good. Light comes back? Next thing;
2. Check the condition of the air intake (the tube and seals) between the MAF sensor and intake manifold. And check the condition of all vacuum hoses.
3. The next obvious thing would be to check the MAF sensor.

wookie66

Appreciate the sound advice and will give it a go and will post outcome on completion

Cheers

forgotmyname

This is the issue with fault codes. It still takes someone with a brain to decide the next step.

Front sensor fault, But was it faulty or getting data out of range for some other reason?

Partially blocked injector underfuelling, Or its detecting less are than there really is and leaning the mixture off.

A decent mechanic will test to see why and when the fault occurs. Not just read the code and replace the parts until the code goes away.

Buy your own code reader. From £10 upwards.

colino

As I've said before, P0420 is a licence to print money (deliberately) or by accident by the incompetent. You said yourself that the car was driving fine (surprisingly with a dodgy cts and O2 sensor it would have been drinking fuel). Especially as the car is in its middle age, you have to check the fitting of the O2 sensor and every bit of the exhaust for a pinhole leak. That would trigger P0420 too.

C_Mababejive

Here you go...

wookie66

Yes i appreciate this requires a lot of detective work and is designed intentionally or not to line the pockets of audi garages but as a lay person its extremely infuriating when the EMS light goes on and it could be anything from a minor fault to one costing over £300 to repair ie cat converter

I have booked my car into my local reliable independent garage and crossed fingers I shall pass on some of the leads from this forum for them to investigate

Hopefully it can be sorted with a bit of gaffer tape!!

C_Mababejive

wookie66 wrote: »

Yes i appreciate this requires a lot of detective work and is designed intentionally or not to line the pockets of audi garages but as a lay person its extremely infuriating when the EMS light goes on and it could be anything from a minor fault to one costing over £300 to repair ie cat converter

I have booked my car into my local reliable independent garage and crossed fingers I shall pass on some of the leads from this forum for them to investigate

Hopefully it can be sorted with a bit of gaffer tape!!

Indeed it can.Simply snip 1" of tape off and stick it over the warning light. Job done...keep driving. i promise it works

wookie66

Update on my Engine Management System light

Took my Audi A3 to an independent Audi specialist for diagnostic check on their VAG COM system

Apparently my cat converter has a blockage and the mass air flow needs replacing

Chap advised fitting an original Audi cat but price for this is way out of my budget given age of car:

£800+ for cat and

£190 for MAF inclusive of labour)

I had the catalytic converter replaced in July 2010 at ATS and having looked at the invoice but warranty is only for 2 years....arrgghhhh!

I could fit a non Audi part but chap said it may only last the same amount of time again

He said it would be ok to continue driving but car may start to consume more fuel and may fail its emissions test come the MOT in April 2013

So what to do?? Car is X reg, 100k on clock, in excellent condition and drives fine

I would probably be prepared to spend £500 max to sort these issues out but no more

Any advice would be appreciated i.e. if anyone knows where one can buy a relatively cheap cat converter for an Audi A3 petrol car since could get a mate to fit it as he runs a specialist exhaust outfit