Lamda sensor fault code... Weird...

[e34.535i.sport]

RE: Recent thread about rough running...

I took a trip to see our Mutual friend Whiskychaser yesterday as he kindly offered to help me out with a few things (what a guy! :D)... I expected to find a sensor out of whack - check the voltage and change the bugger. Not as simple as that unfortunately!

We found that the car had a Lamda Sensor fault code stored (28) (o2 sensor)- And after inspection I don't seem to have one! I had it on the ramps this morning and couldn't find it - Although RealOEM suggests I do have one on top of the cat when I put the VIN in... What is also weird is that I don't seem to have a cat!

The exhaust system that is on there is OE BMW part all the way along, and is probably less than 2 years old as I think it was recently done when I puchased the vehicle.

Does anyone have any possible scenario's for what's going on here? I know a vaccum leak could cause a code like that but that is definitly not the case - I've exhausted that route beleive me. Should I have a CAT and o2 sensor???

Could the PO have had an exhaust put on without a CAT when it should have one? Would the car run ok if this was the case? It's had two emissions tests since then and it passed with flying colours.

The only symptoms I'm having are poor running (nothing terrible but just not as smooth and responsive as I'd like.) and reduced performance gradually returning after resetting by disconnecting the battery. The idle isn't great generally but not too bothered about this really... I just want the car to perform as it should.

Oh, and we cleared the code from the DME and on the motorway trip back home the car was flying... It felt much more responsive (possibly a placebo but felt much better). Could a code stores from a previos problem still cause issues even if the problem is fixed?


Thanks for all help and advice...

EDIT: Spark plugs are fairly recent too!

[bad_manners_god]

Well, judging by the pics on RealOEM.com the O2 Sensor is located at the entrance of the Cat, so the Cat itself would not affect the O2 reading.

The only thing the Cat would affect is the amount of backpressure.

Although, if there is no O2 Sensor, your CEL should be on. Also, if there is no O2 Sensor, you would defiently be getting crappy performance.

[Ferret]

Have you got the wrong EAT chip installed?

A lot of the 535i's were built without cats - they use a different open loop software system and make a fair few assumptions about what the car's doing.

Your ECU shouldnt be capable of throwing an O2 sensor code if it wasnt originally fitted with a sensor.

Is there wiring still there for a sensor at all?

[whiskychaser]

Thanks for the character reference:D I dont think you will get a check engine light unless somebody has done some fancy wiring on yours-the stomp test doesnt work on euro cars after all. Although my car is newer (though not as shiny!) it has never had a cat or O2 sensor either. If I put my VIN in, it doesnt even give the option of one. I guessed yours was a June build and realoem does. Bentleys only lists one DME for the 535i but as its only aimed at the American market that may explain it. I cant see somebody putting an OE exhaust in and then just snipping off the sensor. I know we reset the fault and at idle it didnt come up on retest. Not had a problem before but I do wonder if my kit was telling us porkies:(

[e34.535i.sport]

Bad_Manners - No Check Engine light, but performance isn't what it used to be. It's interesting though that it used to perform well... but gradually got 'less good'.

Ferret - I will defo check on the EAT chip. We've had this conversation before I think but it works and no CEL so I haven't bothered so far - Will I need to talk to Mark D over this? It seemed to increase performance when I put it in but it is since after I got the chip it has been getting worse now I think about it. I will try putting the normal chip back in and see how it goes too. I could see nothing at all looking all the way down the exhaust in terms of wiring, and no sign of a cat. It's weird then that it's throwing that code isn't it... I'm a little worried to be honest!

Whisky!!!! - Hey there 'friend' (I'm not a billy no-mates anymore ;)), Mine is 01/08/1990 build and the CAT shows up on RealOEM for me which is very, very weird. I can't see the machine giving us wrong info... Was the dogs b*llocks!

I'm freaking out!

[Paul in NZ]

Bad_Manners - No Check Engine light, but performance isn't what it used to be. It's interesting though that it used to perform well... but gradually got 'less good'.

Ferret - I will defo check on the EAT chip. We've had this conversation before I think but it works and no CEL so I haven't bothered so far - Will I need to talk to Mark D over this? It seemed to increase performance when I put it in but it is since after I got the chip it has been getting worse now I think about it. I will try putting the normal chip back in and see how it goes too. I could see nothing at all looking all the way down the exhaust in terms of wiring, and no sign of a cat. It's weird then that it's throwing that code isn't it... I'm a little worried to be honest!

Whisky!!!! - Hey there 'friend' (I'm not a billy no-mates anymore ;)), Mine is 01/08/1990 build and the CAT shows up on RealOEM for me which is very, very weird. I can't see the machine giving us wrong info... Was the dogs b*llocks!

I'm freaking out!

mine is also a non cat car but it doesnt say it NOT having one on real oem

[e34.535i.sport]

mine is also a non cat car but it doesnt say it NOT having one on real oem

Hey thats good to know, now I'm just wondering why it threw the code... Could have had a vacuum leak before I got hold of it I suppose, but I don't know.

[whiskychaser]

This is bugging me - but I like puzzles so does this sum it up? :
1. You dont get a CEL.
I would say you never will cos they arent connected on Euro spec cars
2. We got code 28
Either my kit is up the wall or the DME is throwing a wonky code.
( I asked my local BM place if they had heard of it - chocolate and fireguard come to mind)
3. Its better if you disconnect battery or wipe the code - for a time.
Something is telling the DME there is a problem. Maybe check the input at the DME pin where the O2 signal is supposed to go? I know the reading is roughly 450mV but that may be AC. (If it is, you can block the DC element out ) Maybe someone can confirm?

[e34.535i.sport]

This is bugging me - but I like puzzles so does this sum it up? :
1. You dont get a CEL.
I would say you never will cos they arent connected on Euro spec cars
2. We got code 28
Either my kit is up the wall or the DME is throwing a wonky code.
( I asked my local BM place if they had heard of it - chocolate and fireguard come to mind)
3. Its better if you disconnect battery or wipe the code - for a time.
Something is telling the DME there is a problem. Maybe check the input at the DME pin where the O2 signal is supposed to go? I know the reading is roughly 450mV but that may be AC. (If it is, you can block the DC element out ) Maybe someone can confirm?

Hey - thanks to going to all that trouble for me! I wouldn't even bother ringing the dealership here in Liverpool - They have no idea what you're talking about half the time... And that's when you've only got as far as "Hello"... LOL! :D

Checking the input sounds like a plan if it degenerates again, as it has been better since we reset it (I had disconnected the battery a week previous)... I might have to ask for your services again on that one though??!!! :p I'll bring the Clay bar down and shine up the whiskymobile in return of course [That's as far as my skill goes!!]. (In response to previous comment - no offence meant at all! :))

[e34.535i.sport]

OMG - I was just reading through Ross's post on Drivabiliy and Idle trouble and spotted something...

When I was searching for Vacuum leaks I pulled the oil dipstick/filler cap a couple of times and the idle worsened greatly - could this have triggered the Lamda/o2 code and kept it in the memory despite disconnecting the battery and not having an o2 sensor???

[bad_manners_god]

OMG - I was just reading through Ross's post on Drivabiliy and Idle trouble and spotted something...

When I was searching for Vacuum leaks I pulled the oil dipstick/filler cap a couple of times and the idle worsened greatly - could this have triggered the Lamda/o2 code and kept it in the memory despite disconnecting the battery and not having an o2 sensor???

I'm pretty sure disconnecting the battery and releasing the charge in the capacitors would erase the code.