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gcbimmer
04-03-2009, 08:33 AM
On my 1993 325i manual, my CEL came on and the scan came up as an o2 sensor. I replaced the o2 sensor and all was good. Now the CEL light came back on after about 3 weeks. I've been driving it like this for a couple of weeks and it periodically turns off. Any ideas? The code comes up 1221 again(o2 sensor). If it were a bad o2 sensor, wouldn't the light stay on all the time? Anybody have any ideas?
Adam318is
04-03-2009, 10:27 AM
Either the O2 sensor wasn't wired correctly, or you have a vac leak.
Jim Spence
04-03-2009, 12:31 PM
Mine did the same thing, same code. Turned out that I had a headgasket problem which was allowing antifreeze into the #6 cylinder, and the sensor was reading that.
Adam318is
04-03-2009, 12:35 PM
Holy s***, didn't know a head gasket problem could throw a CEL but I guess it would make sense. OP, hopefully that's not what it is, but I would think you would have noticed something awry by now if that was in fact your problem.
Jim Spence
04-06-2009, 04:48 AM
I didn't notice anything. The car ran fine; no oil in the coolant or vice versa. Just coolant getting into the cylinder and burning off. I had it fixed, and now - no coolant leaks and no dangblasted CEL.
gcbimmer
04-07-2009, 09:28 AM
Thanks guys. I did a visual check for vac leaks and everything "looks" good. How do I know if it's the headgasket? And I certainly hope it's not. The car runs great, good smooth power throughout acceleration in all gears. The idle was jumpy at times when rear defefroster was on and the heat was on high. But with the change in weather and not using the def & heat as much it has not been happening. I tried it just the other day with all on and it idled fine.
C Sean Watts
04-07-2009, 01:53 PM
On my 1993 325i manual, my CEL came on and the scan came up as an o2 sensor. I replaced the o2 sensor and all was good. Now the CEL light came back on after about 3 weeks. I've been driving it like this for a couple of weeks and it periodically turns off. Any ideas? The code comes up 1221 again(o2 sensor). If it were a bad o2 sensor, wouldn't the light stay on all the time? Anybody have any ideas?

The book you have just makes a reference to "O2 sensor? Does it say anything like, "...voltage out of range." or "...indicated values higher or lower than expected."
?

There are several O2 sensor codes.