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GM Locking Gas Cap Causing Problem??

C

CapeCodBlue

GUEST
We have had a problem with our "Service Engine Soon" light" displaying constantly. The dealer's service tech said that the diagnostics indicated that there was a slight emissions leak, and that it had been caused by the Locking Gas cap (which we ordered and purchased from the dealer). He claimed that these gas caps don't seal as well as the stock cap, and said that we should replace it with the stock cap. Has anyone else experienced this problem? Makes one wonder why they sell them if they are problematic.
 
I have had my locking gas cap for about 7 months or so without any problems. I bought mine on ebay. I don't see GM on it anywhere but it looks like a factory piece. I have heard of the "service" message appearing when the cap doesn't seal/vent properly. If you bought yours from the dealer you should be getting a replacement that works properly, or a refund.
 
Would this problem be caused by a lack of pressure...would this be the reason it would send up a flag or two.... :B:
 
The gas cap is part of the evaporative emissions system. If the cap doesn't seal properly that part of the system will fail and turn on the light. It doesn't matter if it is the stock cap or an aftermarket. My daughter failed to tighten her gas cap all the way and the check engine light came on. A trip to the dealer cost her $35 for diag and tighten the cap. It has been fine since. :B:
 
I was told the same thing that AVid said. I put an aftermarket locking gas cap on my Silverado and the dealer saw it when they were checking out why my check engine light was staying on. It was a bad sensor, but they told me to take the locking cap off and put the original one back on because that could also cause the light to come on.

I don't know about other states, but in New York, when they do the emissions test on vehicle inspections, they have a part of the test where they do a gas cap test.
 
New Jersey as well....at first I thought the guy was trying to tamper with my gas tank on my old car....until I realized they test as well.... :-[ :B:
 
I have had my locking GM gas cap on for about 1 year now, no problems with it. There are two different caps avaialble, make sure they gave you the right one
 
I have had the Stant locking gas caps for years (usually same as GM) and never a problem. My '99 Bonne got a check engine light and I asked that it be looked into...On the Stant type cap (OEM) you should turn it 3 clicks to lock on...Oh, the reason for the check engine light...what MAJOR repair would I have to make???
Uh, sir your gas cap wasn't clicked all the way... :-[ ;D (y) :B:
 
I just installed a billet gas cap from JP Customs (so easy a child can do it) but there is a new problem in my area with wonderful local children pouring sugar into the gas tanks of heavily modified vehicles (i.e. mine). Tried to get a locking gas cap for 03 Z71 and no one, so far, seems to have one. Anyone know where I can get one that fits?
 
ASAGOT, there is some good comments about the locking gas cap over in the Q&A board. I'll move this into that thread for you to continue the discussion over there.

I was told that the GM part number is;

12495845 - Locking Gas Cap but a search told me it was an old number and the new number is; 12497880. So you may want to try both.
 
ASAGOT said:
I just installed a billet gas cap from JP Customs (so easy a child can do it) but there is a new problem in my area with wonderful local children pouring sugar into the gas tanks of heavily modified vehicles (i.e. mine). Tried to get a locking gas cap for 03 Z71 and no one, so far, seems to have one. Anyone know where I can get one that fits?
I got one from my local dealer here in Texas. I too have an '03 Z71. I've had it since April or May and haven't experienced any problems thus far.
 
I have a GM locking gas cap and it has been trouble free for a year now. I would suspect that some aftermarket locking caps may have issues but GM caps unless defective are fine.

Hey ASAGOT - I believe you mean billet gas door not cap! (y) ;) :)
I also have the Billet door and they are very nice. :D
 
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