ODBII Mysteries on the Volvo S70
 

so now I've connected this scanner onto my S70, and there seems to be so much inconsistencies with the readings, I had the signature low range negative fuel trim going to positive as it gets higher into the rpms, which shows sluggish Air flow sensor, which I've removed and clean, but unfortunately it only improved the fuel trim range a touch...


but the mystery is, I have a total long + short term fuel trim in bank 1 of -10% to -13%, and the total long + short term fuel trim of bank 3 is +10% to +15%, (difference between bank 1 & 3 is close to 30%?!)

Now as far as I know the 5254S is a straight 5, and so there should only be 1 bank of injectors, so where is bank1 and where is bank3? (The scanner reports that bank2 doesn't exist) but going by the idea that there's only 2 oxygen sensor, 1 pre-cat and 1 post-cat, so how does the ECU work out the fuel trim value for bank 1 and bank 3?! Or is the returned value of bank 3 is actually an error that we should just ignore it?


Also another mystery is the 0V readings on the oxygen sensor #2, there is so much thread on google regarding the same problem but no one seems to be able to work out why, although they all went ahead and changed both their sensors and tested the wirings, but the ECU continues to return 0V, anybody know why?


Also forgot to add that when the accelerator pedal arent depresses, the scanner would still report the TP as more than 10%! Not sure if this will affect performance or economy?