3.0, 91 4 runner, auto, 400,000 kilos.

I've searched and read for hours but was unable to find a post with the same symptoms as my truck. Hot or cold start the check engine comes on at start up and stays on for a dozen or so kilometers. When it does go out it fades out it doesn't just turn off. It doesn't seem to be rpm related in any way and alternator was changed mid winter , this just began happening today. All fluid levels are good. Any ideas? I'll check for codes
(once i remember how) in the next day or so and report thise back here if noone has any ideas



Derek

 

Not sure if it will matter but it has been pretty rainy and wet for a day or two.