Yet another O2 sensor replaced...part warranty this time!

[Izice]

Well the cars been in the garage again for another lamda sensor replacement. Managed to last 1 month since the stealers replaced it before it threw a fault.

Fortunately the Stealers replaced it under parts warranty but threatened to replace the ECU if it happens again :roll:

I don't really think the stealers know what their doing....in total in the last 1yr and 1/2 i've had x5 lamda sensor replaced. x1 in AUC and x3 paid for.. and now this for free under parts warranty.

The codes thrown up by the engine management fault were all related to the O2 sensor being the issue....why are the stealers now threatening to stop honouring their part warrant (2yr) and angling for a new ecu when the faults don't relate to this in the codes?

Seems to me the fault diagnostics done by the techs involves a prescribed procedure of plugging in a pc and changing parts which it tells them to do without thinking why the fault is reoccurring.

It's seriously taking the joy out of my motor and im considering contacting BMW UK.

Any advice is welcomed.

 

[DPG]

5 x O2 sensors replaced? is that how many a Z4m has?

 

[AndyBeech]

Something else is obviously amiss and they're putting it down to the DME for whatever reason being at fault. The O2 sensors failing are clearly a symptom of another fault in the chain rather than the sensor itself. Is the car running rich as I've heard this can cause sensors to fail prematurely. Any other issues with your car engine wise?
I guess if they want to replace your DME under warranty it wouldn't be a bad thing, would cost about a grand outside of warranty so if that's the way they want to go then let them do it, it might well be the cause of the problems your having.

Car has 4 sensors altogether, 2 pre cat and 2 post cat (or is it 1 post cat?). Is it the same position sensor that keeps failing?

 

[beanie]

as Andy says, there must be a problem elsewhere for the sensors to keep on failing. There's just no way you'd get so many faulty ones.

I'd be inclined to whip out the plugs to see what they look like. You'd have hoped this would be one of the first things done by the 'techs' but it appears you've got computer jockeys rather than mechanics doings the fault finding. That said, if they're going to foot the bill then perhaps you can just let them carry on replacing parts!

As per Andys question, how is the car running? Is it smooth and progressive or jumpy and reluctant to rev?

 

[Dogmatic6]

I've had my M for almost 6yrs and I've had one O2 sensor replaced in that time. Luckily it was within the first year so replace under BMW Warranty.

There must be something else going on here.

 

[AndyBeech]

as Andy says, there must be a problem elsewhere for the sensors to keep on failing. There's just no way you'd get so many faulty ones.

I'd be inclined to whip out the plugs to see what they look like. You'd have hoped this would be one of the first things done by the 'techs' but it appears you've got computer jockeys rather than mechanics doings the fault finding. That said, if they're going to foot the bill then perhaps you can just let them carry on replacing parts!

As per Andys question, how is the car running? Is it smooth and progressive or jumpy and reluctant to rev?

Agreed on the computer jockeys point, shame these days that main dealers seem to just do whatever the computer tells them rather than actually getting stuck into the mechanical side of the engine and actually diagnosing a problem. INPA, DIS and ISTA are great tools which can tell you a lot about what's going on in the engine but it's no substitute for actually looking into the engine itself. Any other garages you can take it to under warranty or are you stuck at the stealers your currently using?

 

[Izice]

Thanks for all the replies.....bit of an update.

X4 O2 Lamda sensors, x2 pre and x2 post catalytic converter.

The cars not under any warranty, AUC warranty expired about1 1 1/2 yr ago. Parts are covered though when replaced by a 2 yr Guarantee when you pay for them. This is why they did the O2 sensor for nothing. but like i said they are threatening to replace the ECU if a problem occurs again with the O2 sensors.

So im looking at £1000 for an ECU? (no warranty)

Does anyone know if a faulty ECU would cause O2 sensors to fail?

I have an angle though when they advise changing the ECU....im going to pay the £1000 and request the old ECU. If after the replaced new ECU is installed and the inevitable happens i will request they reinstall my old ECU and refund me my £1000.

I don't believe they have done any leak tests on the exhaust system or tried upgrading software on the ECU...nothing just the blinkered approach of changing sensors and not investigating why the go bad.

I use nothing but V power Shell. 38,500 miles 2006. No mods except the mandatory stubby

 

[CornishRob]

I use v power only. I find it to run the best and give the best mpg

 

[AndyBeech]

Thanks for all the replies.....bit of an update.

X4 O2 Lamda sensors, x2 pre and x2 post catalytic converter.

The cars not under any warranty, AUC warranty expired about1 1 1/2 yr ago. Parts are covered though when replaced by a 2 yr Guarantee when you pay for them. This is why they did the O2 sensor for nothing. but like i said they are threatening to replace the ECU if a problem occurs again with the O2 sensors.

So im looking at £1000 for an ECU? (no warranty)

Does anyone know if a faulty ECU would cause O2 sensors to fail?

I have an angle though when they advise changing the ECU....im going to pay the £1000 and request the old ECU. If after the replaced new ECU is installed and the inevitable happens i will request they reinstall my old ECU and refund me my £1000.

I don't believe they have done any leak tests on the exhaust system or tried upgrading software on the ECU...nothing just the blinkered approach of changing sensors and not investigating why the go bad.

I use nothing but V power Shell. 38,500 miles 2006. No mods except the mandatory stubby

Ok that changes things a bit.

First thing, the DME cost was a rough guess, however RealOEM lists it at around £800 plus VAT, labour for fitting, programming etc so £1000 at least would be a fair estimate I would think at a stealers in any case.

I would be very careful using the angle your suggesting, they may well say that the DME *might be* at fault but that's no guarantee that is the problem, hence I would imagine they owe you nothing if it doesn't fix the problem and as a dealer will just keep changing likely failed components at your cost until they do fix it. Unless the DME is specifically showing an error code for itself and they can prove and guarantee 100% that it is the problem, I would not be changing it. I have no idea how a faulty DME would be causing o2 sensors to fail, sounds like a very unlikely scenario to me. Faulty wiring to the DME yes potentially, but an actual failed unit....I've never come across that so far, and not on such a low mileage engine.

What I would do is take it to a respected independent and actually get to the root of the problem rather than computer guesswork which is what it sounds like. It might be something as simple as a faulty MAF making the car run overly rich and fouling the sensor. It could be a faulty wire, bad connection, short circuit somewhere or a bad earth. If they just go down the route of changing sensors until its fixed your going to be footing a hefty bill potentially at the end of it!

 

[TomK]

sensible advice

This^^^. Like you I struggle to believe a that a faulty dme is plausible in the first instance, and that it would 'caput' sensors if it was, though I am no expert. Are there even any instances of failed dme's out there? I've not heard of it to be honest.
Your 'backup' plan of reimbursement won't go too well I suspect also, it's not how the dealers operate.
The trouble with many BMW dealerships these days is that there are few techs familiar with our 'old' engines. Since you are not in warranty, get shot of dealer asap and take it to a specialist.
Where are you located? I'm sure someone can recommend a respected indy close by.
Get it looked at asap, sensors failing like you're describing suggests something more sinister than the usual.
Best of luck.

 

[Izice]

Thanks for all the replies.....bit of an update.

X4 O2 Lamda sensors, x2 pre and x2 post catalytic converter.

The cars not under any warranty, AUC warranty expired about1 1 1/2 yr ago. Parts are covered though when replaced by a 2 yr Guarantee when you pay for them. This is why they did the O2 sensor for nothing. but like i said they are threatening to replace the ECU if a problem occurs again with the O2 sensors.

So im looking at £1000 for an ECU? (no warranty)

Does anyone know if a faulty ECU would cause O2 sensors to fail?

I have an angle though when they advise changing the ECU....im going to pay the £1000 and request the old ECU. If after the replaced new ECU is installed and the inevitable happens i will request they reinstall my old ECU and refund me my £1000.

I don't believe they have done any leak tests on the exhaust system or tried upgrading software on the ECU...nothing just the blinkered approach of changing sensors and not investigating why the go bad.

I use nothing but V power Shell. 38,500 miles 2006. No mods except the mandatory stubby

Ok that changes things a bit.

First thing, the DME cost was a rough guess, however RealOEM lists it at around £800 plus VAT, labour for fitting, programming etc so £1000 at least would be a fair estimate I would think at a stealers in any case.

I would be very careful using the angle your suggesting, they may well say that the DME *might be* at fault but that's no guarantee that is the problem, hence I would imagine they owe you nothing if it doesn't fix the problem and as a dealer will just keep changing likely failed components at your cost until they do fix it. Unless the DME is specifically showing an error code for itself and they can prove and guarantee 100% that it is the problem, I would not be changing it. I have no idea how a faulty DME would be causing o2 sensors to fail, sounds like a very unlikely scenario to me. Faulty wiring to the DME yes potentially, but an actual failed unit....I've never come across that so far, and not on such a low mileage engine.

What I would do is take it to a respected independent and actually get to the root of the problem rather than computer guesswork which is what it sounds like. It might be something as simple as a faulty MAF making the car run overly rich and fouling the sensor. It could be a faulty wire, bad connection, short circuit somewhere or a bad earth. If they just go down the route of changing sensors until its fixed your going to be footing a hefty bill potentially at the end of it!

Thanks again for all the good advice. I've searched the American Z4 forums and the failure of an ECU is almost unheard of and like the commentators here im highly sceptical of their reasoning.

sensible advice

This^^^. Like you I struggle to believe a that a faulty dme is plausible in the first instance, and that it would 'caput' sensors if it was, though I am no expert. Are there even any instances of failed dme's out there? I've not heard of it to be honest.
Your 'backup' plan of reimbursement won't go too well I suspect also, it's not how the dealers operate.
The trouble with many BMW dealerships these days is that there are few techs familiar with our 'old' engines. Since you are not in warranty, get shot of dealer asap and take it to a specialist.
Where are you located? I'm sure someone can recommend a respected indy close by.
Get it looked at asap, sensors failing like you're describing suggests something more sinister than the usual.
Best of luck.

I'm currently near Dumfries South west Scotland, i don't know of any specialist garage around here? but i would be willing to travel few hours each way to get this sorted (if a sensor goes again). I really need a stable base to build upon, looking to upgrade alloys and get a supercharger but with these persistent failures i'm reluctant to proceed.

The cars running sweet just now, enjoying the weather rag top down, but the fear still exists that the next warning light is just round the next corner or is that the police camera van or both