2007 Chev Classic 1500 - 4.8L (V) Check Gas Cap

[hardings]

HELLO. WE HAVE A 2007 CHEVY CLASSIC 1500 V8 4.8L(V) AND KEEP GETTING CHECK FUEL CAP LIGHT COMES ON.

REPLACED FUEL CAP WITH A AFTERMARKET FUEL CAP. EVERYTHING WAS GREAT EXCEPT FOR THE LIGHT COMES BACK ON. CUSTOMER HATES THE DING NOISE! DINGS AT 3/4,1/2 AND 1/4 WHEN IT RUNS ITS EVAP TEST. SO OUR NEXT STEP WE TOOK WAS REPLACING THE EVAP VENT CYLANOID(FROM GM). REPLACED THAT BECAUSE THE VALVE WAS STICKING. BUT WE HAD ABSOLUTELY NO CODES EVEN WITH LIGHT ON. SO CUSTOMER TAKES VEHICLE AND IS ON HIS WAY. DING, YOU GUESSED IT LIGHT CAME BACK ON. SO WHAT WE DID WE GOT A GM GAS CAP.DING! DIDNT WORK.

HOPING FOR SOME INSIGHT IF YOU HAVE RUN INTO SAME ISSUE. ANY HELP IS WELCOME. THANKS!!!

[brianp87]

Have you smoke tested the system? You dont get any codes a 455 or 442? You should get one code. I would leak test before replacing anything. We get these periodically but nothign that stands out or that we cannot find with the leak test

[ricmorin]

The Gas Cap message comes on when the large leak test fails. Have you done a smoke test on this? Using the Tech2 or a good scanner, you should be able to command the vent valve closed and open the purge. You should see a change in FTP. When you replaced the vent valve, did you use the relocation kit the GM has now for those? Curious that there were no codes. I would suspect there would be a large leak code at least pending. What are you using for a scanner?

[hardings]

WE HAVE DONE MULTIPLE SMOKE TESTS. NOTHING COMES UP. NO CODES NO SMOKE. HAVE A VERUS AND GM TECH2 TOOL USED ON VEHICLE. UNDER EVEN MODE 6 THE EVAP SYSTEM IS PASSING THE TESTS. THANKS FOR THE QUICK RESPONSE

[hardings]

ALSO WE RELOCATED THE CYLANOID PER GM

[ricmorin]

WE HAVE DONE MULTIPLE SMOKE TESTS. NOTHING COMES UP. NO CODES NO SMOKE. HAVE A VERUS AND GM TECH2 TOOL USED ON VEHICLE. UNDER EVEN MODE 6 THE EVAP SYSTEM IS PASSING THE TESTS. THANKS FOR THE QUICK RESPONSE

Since you have a Tech2, check the IPC for failure codes. Perhaps the light is coming on when it's not being commanded?

[hardings]

COULDNT FIND ANY CODES IN THE IPC WITH EITHER TOOL. IM ON THE HUNT TO SEE IF THERES ANY REFLASH PROCEDURE TO CURE THIS. DONT BELIEVE SO

[ricmorin]

Sounds like an IPC problem. Can you get in there with the Tech and see any relevant data pids? GM has lots of issues with IPC's, but I haven't heard of this one before.

[ricmorin]

These IPC's can be reprogrammed using the Tech and TIS2Web.

[hardings]

does anyone know if there is a way inhouse to determine what or when the last ipc reprograming was for this truck? dont have much history on truck i can get my hands/ears on

[steven kiser]

if you have a good relationship with the dealer they'll run the vin. i think that there is a way to read it through the tech 2. it's been a while but i know that on some applications there will be the update # on the screen. another point that i adhere to is if it wasn't done at my shop or the dealer then as far as i'm concerned it wasn't done..

[ricmorin]

Yes, With TIS, when you request the data, you can see all the versions of the programming for that module. It doesn't usually tell you dates.

[hardings]

I might have to possibly go with the reprogram with the ipc. im not sure if its been done yet thats the only thing that concerns me. but just like any system if the parameters need to be moved so display doesnt come on it is what it is

[steven kiser]

has this person been using alternate fuel? i just looked at all the tsb's on this truck and it was like reading war and piece. had to stop to get my eyes to focus.........

[hardings]

uses regular 87 octane fuel no alternatives

[hardings]

believe the fuel tank pressure sensor was bad causing the system to purge at inaccurate time causing our light issue. pulled off sensor and had some fuel in it. belive we have a triple clicker at the gas station. will call customer monday and post as fix if no ding

[steven kiser]

man, don't you just love people that will squeeze every drop they can into the tank. sometimes i think that they feel that suddenly no gas will be available nationwide........then there are the others that will dump the left over lawn mower or snow blower gas into the tank. i always get a few in the spring that have new snow blowers that use 2 cycle and the vehicle is towed in smoking or running rough.

[hardings]

replaced the fuel tank pressure sensor and light is still going on. going to do more studying and see if we can finally get to the botom of it

[steven kiser]

still waiting for a few answers. nothing really on direct hit so i called a couple of buddies at g.m. this system has been smoked and filler neck isn't distorted from a drive away is it?

[steven kiser]

just got a bit of information on this. it doesn't have to be a large leak to cause this. i spoke with a tech that told me he's had more than a few times where a cracked hose has caused this with no codes being thrown. he said to carefully look at all hoses and connections. out of 10 he's found it to be a hose being cracked 9 times. he said while smoking the system to use a scanner and activate all valves and also to see if they close on demand as well. good hunting.................................