Recently purchased a 95 touring from my elderly neighbor. Check engine light was on, when I purchased it, code is 1221 (Oxygen Sensor #1).
I have replaced the oxygen sensor and the MAF.
After 20 minutes or so, check engine light comes back on and the fuel then runs super lean.
Searched the forum and other websites. No clue what to check/replace next.
Any ideas?
Check your fuel pump, it could be starting to fail as it gets hot. I had the same problem when I had a failing pump.
1995 525i 5-speed - Thread
I threw out the whole fuel system chasing this. Fuel pump, fuel filter, lines, fuel pressure regulator, injectors, and even a compromised harness can all cause insufficient fuel delivery.
1221 can have many causes https://www.bimmerforums.com/forum/s...nsor-code-1221
https://www.bimmerforums.com/forum/s...gine-code-1221
Last edited by shogun; 07-26-2023 at 10:12 PM.
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