BMW Fuel Trim
So I am trying to get a better understanding on BMW fuel trims. Vehicle came in for CEL and parasitic draw. Snap-On Verus Pro and Matco Maxgo scan tools were used. Also this vehicle sat for a month because I got slammed with other work cause the customer was out of town and we were down some employees, so I will try and recall all the information correctly.
CEL codes were as stated above. After some time of reading I had found that on the Maxgo engine pid’s that the Adaptation mixture additive bank 1 & 2 were around .1-.15 ms. From my understanding is that these numbers are long fuel trims at idle. My adaptation mixture multiplicative bank 1 & 2 were at 0%. These fuel trims are long term off idle and under load through the higher RPM ranges. The last pid’s were oxygen sensor controller bank 1 & 2. These were reading around .95-1.07. These fuel trims to my understanding are short term fuel trims.
So I read for the Adaptation mixture additive anything above or below .2 ms is to rich or lean. Well since I could not find any way of figuring out the codes. (some forum did say the codes meant a rich condition. Did not know how trust worthy that was) I decided to smoke test the intake system since it seemed like the vehicle may have been running lean. What do you know intake boot ripped wide open. So awesome! Replaced it and my Adaptation mixture additive went to 0.02 ms. Oxygen sensor controller was at .97-1.01 either bank. Okay were getting some where.
Test drove it and when I came back found the adaptation mixture multiplicative was at -5.30%. So did some more reading and read that anything above or below 8% was to much. But also read that if I see -5% look for plugged cats….okay.
So here I am now asking you all for help. My questions are as followed:
- Is my interpretations of the fuel trims correct?
- What Should my adaptation mixture multiplicative & Adaptation mixture additive be on a normal good running vehicle?
- Also where the hell can I get code descriptions and code setting criteria at?
Also to make note on the Verus Pro I have O2 integrator %. Fuel trims part load %. Fuel trims idle load ms. These seem to be just a translation of the oem pid read outs. I been really wanting to get into diagnosing euro vehicles so my shop has been accepting them and being really patient with me learning on these vehicle. Also the clients that own the vehicles have been very patient with me keeping the vehicle longer to try and understand them. So any info would be great. Any online Euro classes for drive ability that any one can recommend would be great also.
Your interpretation of the fuel trims looks correct to me. If you are getting into Euro vehicles, I wouldn't use Snap-on. Too many times I've come across incorrect data, incorrect fault codes, and one time it was actually causing faults to be set. Imagine trying to figure out why a fault code won't go away, only to finally figure out that the Snap-on scan tool was causing the fault to set. I…
I am weak on Euro and they have always been a challenge for me. I keep on learning, maybe I have been using the wrong tools LOL
Steven McGrew Seeing you are also from Spokane, i think i just found my euro guy "to ask for advice" 😁
You will need OEM scanner or Autel or Autoland scanner for data information. Snap On too weak,
Well unfortunately it will be a while before I can get my hands on those tools. I have been really wanting an ross tech vcds and the autologic. Just cant afford them right now till I get some of these others scanners paid off a little more.
When it comes to fuel trim codes I ditch the Autologic blue box in favor of a generic obd2 scanner. Doesn't mater the brand chase a lean code like any other car. I work on a fare amount of BMWs and get the job done. Those era BMWs like to through fuel trim codes whitout saying rich or lean