I have a 99 M3 (E36), and the check engine light won't go away. The BMW
dealer has replaced the oxygen sensor, gas cap, and done a tune-up on one
visit. The light came back on in a few days. After that the computer was
reset, but again the light came on in a few days. I got the following info
from the dealer:
I PULLED THE FILE ON YOUR CAR. IT HAD 254 TIMES BETWEEN VISITS A MAJOR TANK
LEAKAGE DECTION. THE DME HELD CODE P0144 WHICH IS A MAJOR TANK LEAKAGE
FAULT, NORMALLY EITHER A GAS CAP IS LEAKING OR THE CAR WAS FILLED UP WHILE
I never fill up my car while it is running, and I always tighten the cap as
far as possible. Another mechanic has also thoroughly gone over the gas
tank and fuel system, and found nothing.
Any ideas on where to go next?