Bad gas cap even after replacing?

Hi all - lurking a few months - great resource going on here! My first question:

My 2004 TRD Xcab threw up a CEL, Advance tells me it's for the gas cap so I purchase and 2 months later the light is still on. Disconnected the battery and had Advance check again - bad gas cap! Don't think I got two bad gas caps, so any thoughts on this matter? Thanks a bunch all.

 

Welcome. Wish I could help you I’m sure someone will chime in some info

 

Welcome....

Btw, what code are you getting?

 

Welcome!

Are you replacing with OEM or aftermarket? Could be that but I’m not totally sure

 

Replaced with OEM. Advanced read the codes - not sure.

 

Need the code for us to be helpful

 

P0440? If so, you prob need to replace charcoal canister. Get it smoke tested.

 

Yeah, get your own code reader... They are pretty cheap and invaluable. I have a blue tooth one I got for

for Android Phones ONLY - Wireless Bluetooth Diagnostic OBD2 Scanner Car Code Reader and Scan Tool for All 1996 & Newer Vehicles ELM327 Compatible OBDII

$20 on amazon and it works really well with the Torque Pro app ($5).

Those autoparts store monkeys just tell you what the most likely scenario is for whatever code they get - they are hardly mechanics.

I'm betting you're getting the P0440 code. The gas cap thing IS typically the most common cause of the code, however that's not the only cause. Basically anything in the EVAP system can be bad. Saturated charcoal canister, fuel vapor pressure sensor, etc...

 

If all codes have been cleared using a scan tool and you have a P1000 code (System not Ready) then you can proceed with getting all the smog monitors to run and set. The vast majority of them will run without having to do nothing more than just drive the truck. The Evap monitor, the most "difficult" one to run has a very specific set of parameters that need to happen before it will start its check. The fuel tank HAS to be between 1/4 and 3/4 full. The coolant temp sensor HAS to be within 10 degrees of the Intake air temp Sensor AND the truck has to sit undriven a minimum of 8 hrs. This sounds difficult but all it means is fill the tank 1/2 way and let it sit over night. This HAS to be done 2 times for the evap monitor to run. Do that and get the codes checked, both pending and current. Like mentioned above, they went for the easiest part to put on, the gas cap.

 

I've had the battery disconnected (which resets the emissions checks) for a myriad of reasons over the many years I've owned my truck, and it's never thrown a CEL for the emissions checks.

Last time was a few months ago when I was welding my sliders on, and then I realized my reg was due and I needed a smog cert. I drove it around for a week and it still didn't clear the final evap check. I checked for codes multiple times and never got a P1000 code, didn't get any codes, actually. It would just show "incomplete" for the evap monitor.

Still passed smog, though...

 

Mine was the purge valve and canister when I had a P0440.

 

up to a certain year vehicle in certain states you were allowed to have 1 or 2 incomplete monitors and still get an emissions check and pass.

The lack of a P1000 code is more than likely due to the scan tool used. Some scan tools say Not Ready, some say Incomplete. I advise my personal customers to not fill their tank fully at least twice a year just so the monitor will run.

 

Needs advise, dealer replace OEM gas cap and 2 days later engine and traction light again, took it to another mechanic and notice smoke coming from gas cap. thanks

 

I had same issue turned out to be the filler tubes were corroded and leaking. I have my own smoke machine got sick of throwing parts at a problem.

 

Threw a cheeepo eBay set on and working great!

 

Thanks, Thad, the technician stated that smoke is coming around the gas cap and not front inside fill tube; the gas filler tube was covered during the smoke test. Again, thanks and God Bless.

 

Mine was blowin smoke out of the gas cap also. Quit when I replaced the tubes even with the original gas cap re-installed. Must of been something where the fuel cap O ring sealed?

 

There is no code for a bad gas cap.