"Service Engine Soon" - O2 Sensor Fault

[Ruffan]

It's time for me to solicit some feedback from the community. Please speak up if you have encountered this issue, or know anything about it:

Since I have had the Dinan Stage 2 software installed on my car (February 2009 - the car was 4.5 months old) I have had issues with an Oxygen sensor fault code. When the software was initially installed the techs did some testing to clear any faults that came up from the software. The only code that they noticed was an O2 sensor fault, which related to one of the four O2 sensors. They replaced that O2 sensor and did some more testing, at which point, the same fault code came up. They replaced another O2 sensor and eventually got the code to go away.

Sometime after I got my car back the "service engine soon" light came back on. I noticed NO change in the performance of the car. When I had time I brought the car back to the dealer and they advised that it was the same fault that they experienced previously.

I've had the car back at the dealer a few times since then, and nobody (Dinan or the dealer) can figure out why this fault code keeps popping up. Yesterday (Dec 3, 2009) I picked the car up from the dealer after having the HPFP replaced. The stock software was completely updated and then the most recent Dinan Stage 2 tune was installed. The tech drove the car for at least 10 miles after everything was completed and no faults or warning lights came on. When I turned the car on to drive home the "service engine soon" light came on. I was obviously upset, because one of the goals of having the car in for the past week and half was to cure this issue. Of course, when a tech hopped in the car with me to go for a little drive, the light wasn't on at all, so I decided to just take the car home and deal with it later. 10 minutes into the drive home the light came back on and stayed on for the remainder of the drive.

The sporadic nature of this warning light is consistent with what I've been dealing with for months. Sometimes it's on, sometimes it's not. I never can notice any changes in the car's performance, and neither can BMW's exhaust analysis (to check for ignition retardation). I’ve tracked the car with the light on and never had any problems. I can only assume that the most recent warning light is again for the O2 sensor, even though everyone is pretty sure that the O2 sensors are fine.

The issue must be purely a computer code issue, but it is frustrating to always have a check engine light on, when the car is under a full warranty. I must say that my dealer has been very responsive, and the people who I work with are great to me. Dinan has also been wonderful in their service levels, including sending me some free Dinan gear when the first exhaust that they sent me was marred on the tips.

If you think you’ve come across this issue, please share your experience.

Thanks,

[Ruffan]

awesome