O2 sensor error codes - diagnosis

[johnfm]

This is for a E93 BMW 320i - but I suppose the logic of the diagnosis holds for any car.


Conencted a Creader V to th eBMW.

Got two BMW specific errors:

P114C - Post Catalyst Fuel Trim via oxygen sensor too RICH (Bank 2)

P124C - I CANNOT FIND THIS ERROR CODE ON THE WHOLE INTERNET!

But, the freeze frame fuellign data for 124c suggest the following:

ST Fue trim Bank1 3.11%
LT Fue Trim Bank1 -3.13%

ST Fuel Trim Bank2 0.77%
LT Fuel trim bank2 -5.47%


DOes this suggest the post cat O2 sensor is faulty? Or is it also possible there is a leak in the exhasut, so the O2 is reading high and trimming fuel back as a result?

Any clever mechanic type people care to help?

[r4dcu]

I had a rich error code when I had a crack in my downpipe. Exhaust is possible although I know nothing about BMW or diesels lmao

[Nick3point2]

IIRC leaking exhausts give a lean reading from a lambda.

[johnfm]

thanks guys

Might post this on the BMW forum to see if there are any techs on there.

[phumy]

What is an E93? i only thought there was 90/91/92's

[phumy]

What is an E93? i only thought there was 90/91/92's

[johnfm]

It is the code for the 3 series cabriolet

[adyady1066]

The E46's were prone to cracks around the cat housing where it joins the down-pipes on the cat. I haven't worked on an E90 series yet but they are based off the old E46 and if they use they use the same or similar engines and exhausts it's the first place I'd look from experience. If you look around the cat casing literally where it meets the tubes on both ends there could be a small crack which runs around the casing. You should hear it blowing if you get someone to block off the tail pipe with a rag while you inspect it.

May be in a different world but thought it may help.