After the pounding rain last nite in So.Cal, this morning has been one of the coldest mornings I can remember since moving back from Las Vegas...drastic weather change this is. My car had started w/o any hesitation, as it has been. However, a few miles down the road, my check engine light came on. When I got to my destination, I pulled the codes from the ECU and got the following: 5-3 (Front Right Heated O2 sensor) and 4-9 (undefined) based on the VBX Maxima ECU Decoder webpage. All of the O2 sensors have been replaced 2 summers ago and I don't think that O2 sensors go bad this quickly. I reset the ECU and drove some more and so far the CEL hasn't come back.

Has anyone had similar experience where drastic changes in weather/temperature set off the CEL?

 

Hmm... just read your first few sentences and thought O2 sensors. O2 are not part of the warm-up phase, but once the engine is warmed, 02 gets calculated.

I haven't experienced your problem before. Good luck with it.
Jae

 

Just an update......

24 hours later, no CEL! I guess it was just a fluke. I'm ok with that.