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Ask Gm Tech (Cam) Your Own Question
Gm Tech (Cam)
Gm Tech (Cam), GMC Mechanic
Category: GMC
Satisfied Customers: 1672
Experience:  GM Grand Master Technician 2007. 14 year experience.
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My check engine light was on. It would go off when the

Customer Question

My check engine light was on. It would go off when the temperature got above about 70 degrees. I went to get an inspection (Texas) and it came on during the inspection. The guy at the station said it is most likely a bad gas cap. I bought a new gas cap and bang, it went off and stayed off for 4 days. Now, it came back on and I went to AutoZone and got the codes 0171 and 0174 - too lean. I left the AutoZone and drove about 5 minutes and the light went back off. What could be the issue?I did get gas after the light came on tonight and made sure the cap was secure... then went to AutoZone... then the light went off. WTH?Any ideas?
Submitted: 4 months ago.
Category: GMC
Expert:  david craig replied 4 months ago.

Hi Im David, the codes P0171 and P0174 have nothing to do with a gas cap.

Expert:  david craig replied 4 months ago.

what is the year and model and engine size of your GMC?

Customer: replied 4 months ago.
Why would it come on and go off again? From my limited knowledge, it does not seem logical that it is intake gaskets - wouldn't the light stay on in that case?2004 5.3L 203,000 miles - runs like new.
Customer: replied 4 months ago.
Yukon slt
Customer: replied 4 months ago.
Any ideas?
Expert:  david craig replied 4 months ago.

im sorry for the delay

Expert:  david craig replied 4 months ago.

check for vacuum leaks, unmetered air and replace the intake gaskets.

Expert:  david craig replied 4 months ago.

just checking in to see how its going