[Observer1122]

Brought the car into the dealers last for the third time with an ongoing problem. Initially I just in directly to the dealer who could not find anything wrong, i brought the car in with the management light on and they said the vehicle had just reset itself overnight and there was no problem. Anyway when the problem happened recently I called BMW assist and the tech read the codes

1/ 29e1
2/ 2a2c

These codes seem seem to relate to fuel mixture. I have heard some people have experienced these codes without any effect on the vehicle almost like "ghost codes". Unfortunately in my case i have not been so lucky. Symptoms are rough idle when cold and hesitation when accelerating, fuel can smelt in the exhaust fumes with the left exhaust noticeably emits more smoke. I will say at this point the injectors were replaced just last week by the dealer. After 3 days engine management light is on again and the drive is awful, so will be back in again tomorrow any help would be appreciated.

[Robbie200]

I had exactly the same codes 8 weeks ago. Changed the plugs and no codes for 4 weeks and then it's done it twice since.

The codes relate to bank 2, precat O2 sensor, but I haven't got to the bottom of whether the O2 sensor is the fault or if it's something else causing the fuel trim to go out of range. I will probably change the O2 sensor when the weather gets a bit warmer. I reckon it may also be injectors.

Light has been off for the last two weeks. As you say, the engine runs rather rough when cold.

I had similar codes 6 months ago for the bank 1, precat O2 sensor and a new sensor cured it.

If you get the cure, then please update the thread.

[Sparky68]

Get it on a autologic and check the fuel mixtures in 1,2,3 and 4,5,6 if it is smoking or running rich on either then its likely to be a pre cat o2 sensor

[Observer1122]

Originally Posted by Robbie200

I had exactly the same codes 8 weeks ago. Changed the plugs and no codes for 4 weeks and then it's done it twice since.

The codes relate to bank 1, precat O2 sensor, but I haven't got to the bottom of whether the O2 sensor is the fault or if it's something else causing the fuel trim to go out of range. I will probably change the O2 sensor when the weather gets a bit warmer. I reckon it may also be injectors.

Light has been off for the last two weeks. As you say, the engine runs rather rough when cold.

I had similar codes 6 months ago for the bank 2, precat O2 sensor and a new sensor cured it.

If you get the cure, then please update the thread.

Vehicle is still at the dealer. I will update once I get it back.

[Sparky68]

My O2 sensor looked like this

[Observer1122]

Originally Posted by Sparky68

My O2 sensor looked like this

I would like to think if this were the problem the dealership would have sorted it by now. As there still has been no problem diagnosed the vehicle is in the process of being stripped down for the second time to find a solution to this problem - a real pain.

[Josh1a1h]

Could it be dodgy cats?

[Robbie200]

I doubt if it's cats, as it's the sensor before the cat reporting a fuel trim fault. My car also passed the MoT after the fault occurred - I'd simply turned the light off. I could be wrong of course.....

I did have to change the bank 1 pre-cat sensor earlier this year and I think it's likely this fault is the bank 2 sensor also causing problems. Would seem logical for the sensors to fail around the same time. My car only has 40k miles though.

Still interested to know the diagnosis when the fault is found.

[Observer1122]

Originally Posted by Robbie200

I doubt if it's cats, as it's the sensor before the cat reporting a fuel trim fault. My car also passed the MoT after the fault occurred - I'd simply turned the light off. I could be wrong of course.....

I did have to change the bank 1 pre-cat sensor earlier this year and I think it's likely this fault is the bank 2 sensor also causing problems. Would seem logical for the sensors to fail around the same time. My car only has 40k miles though.

Still interested to know the diagnosis when the fault is found.

I got the car back yesterday. I was told the car had been de-coked, 2 sets of plugs and injectors (first set became were fouled after the car was given a test drive), High pressure fuel pump replaced and on top of that software issues had to be sorted out. The drive feels better and idling is also noticeably quieter. Over time it will become clearer if these fixes had completely solved the problem. There was no mention of any sensors.

[Robbie200]

Many thanks for the update. Not sure I want to change injectors just yet but I might consider the HPFP in the new year.

[AlanYoro35i]

Get the bmw warranty and sit back ,relax.