Just purchased a 1994 GMC Yukon 2 door. It was all stock but changes are coming. While driving it yesterday the service engine soon light appeared. I have been told numerous reasons why it came on but I would.like to know if anybody else has had this happen. Please let me know.
Idiot Light
- Thread starter Joe Graz
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Welcome to the forum! , I moved your post to the correct section, just an FYI make sure you post in the 1991-99 section. As for the check engine light, did you notice any weird gauge readings? or did the truck act funny?
No funny noises or clunking. I had a mechanic check the entire thing and he said it runs fine. I did get the alternator replaced but the light still comes on for a few minutes then goes away.
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My 92 occasionally likes to peak in temp for just a few seconds on first start up for w.e reason the next time that happens check the temp gauge it might be a sticking t-stat
SunlitComet
OBS Jedi-Do Good
engine light on is a sign of a sensor/actuator/data mismatch issue. you will need to invoke the vcm to explain what is going on. read the file below and report back any codes you get. if the light happens to be off at the time wait for it to return then test again.
SunlitComet
OBS Jedi-Do Good
note that there two temperature senders. the one on the thermostat housing is for the computer use only and does deflect its data to the dash as well.
iLikeEggs
Potato!
On pre OBD-2 GM vehicles, if there is a diagnostic port under the drivers kick panel you can pull codes. Take a paper clip and un-bend it into a U-shape. Stick each end into the A and B terminals on the diagnostic port, thus shorting them. They should be clearly marked. Turn on the ignition switch until the dash panel lights up. Count the number of times the check engine light flashes. Three flashes, pause two flashes would be code 32, etc. Google the diagnostic codes for your vehicle and take it from there.
SunlitComet
OBS Jedi-Do Good
been there, said that in post #5 above. and it is called obd11.
iLikeEggs
Potato!
Thank you for the clarification. 
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