Diag Code(s)

[Dace]

I bought a very basic OBDII scanner tool the other day to help troubleshoot a Check Engine light on my 99 M3. The code listed in the trouble log displays as P0170 - Fuel Trim (Bank 1). This code seemed rather ambigious especially since there was really no performance difference or drivability issues.

The car has 64k miles for reference. I cleared the Check Engine light to see if the problem would persist and it did not for nearly two weeks.

Now I have that same 0170 - Fuel Trim code accompanied with P1188 - Unknown Powertrain DTC (Manufacturer Controlled; Fuel and Air Metering). Performance does seem to be slipping as well although not so much under steady acceleration. There is a slight hicup if cruising then followed by steady acceleration although this is rather intermittent. Since it is summer I have been using the A/C on and off so that has also skewed my sense of power for the car.

Another possibly related item is that at idle if I do a few quick flutters of the gas pedal there is a bit of a stutter.

The OBD reader I have is sub par for my liking and gives no data regarding fuel trims short or long term ...or any 02 readings.

I am looking for possible suggestions before i go throwing parts at it.

[Dace]

Yesterday, I started the car and noticed that the check engine light was gone and everything seems to be normal again. Any ideas?

[Wayne 962]

Hi there. Fuel trim is often associated with an oxygen sensor reading.

We have a laptop-based system that is very cool, but I can't find it in our catalog right now...

-Wayne