CarTalk.com Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Check fuel cap message

I was getting this message on my 2009 Honda and bought a new fuel cap, from Honda, which was far tighter. the message persisted for weeks. My mechanic could not pull up a code. I made an appointment w Honda which apparently has a deeper code scanner. The message persisted until the day of the appointment so Honda suggested not to come in since they could not pull a code when there was no error message. Then a week later the message came back and minutes later it went away & the check engine light then went on, and of course it’s the weekend, everyone’s closed. Any ideas?

That’s B.S.

The Honda scanner is capable of retrieving what are called history codes.

These are codes that have occurred in the past and are stored into the computer.

Your vehicle is out of warranty.

Find an independent shop that doesn’t hand you a line of B.S.

Tester

3 Likes

I don’t think there’s any sensor that detects a problem unique to the fuel cap. The engine has an evap system which is intended to keep the fuel vapors (for example those above the fuel in the gas tank) from escaping into the atmosphere, creating air pollution. It’s a closed system in other words. The message is saying the computer probably detecting a leak in the evap system. Could be the fuel cap, but could be other things to. It’s like if you have a deflated tire. You know it has a leak, but it could be anywhere, valve stem, tread, sidewall, bead, etc. The shop is probably trying to save you $$$ b/c looking for a leak can be time consuming, especially if the leak doesn’t even exist.

It seems unlikely, but the leak could be in the fuel cap still. Fuel caps often have 2 valves them. One that allows air to enter the tank to replace the volume of fuel that’s used as you drive, and another to allow air to escape if something unusual causes the tank pressure to rise beyond set limits. And a leak can spring from where the fuel cap mates to where it screws on also. There’s usually a rubber gasket or o-ring. You might try cleaning that gasket and then rubbing a light film of engine oil on it to improve the seal.

The logic that illuminates the “Check Fuel Cap” message isn’t the same as the PCM evaporative emission system leak faults. To record an evaporative system leak fault the PCM must detect the problem twice however for the fuel cap message the leak only needs to be detected once.

Now that the check engine light is on there is a fault stored in the PCM so there will be something to investigate.

1 Like

Did you clean the lip of the fuel filler pipe where the gas cap’s gasket makes contact? Rust. residue from the old cap’s gasket, and other assorted muck can prevent a good seal. Be careful not to let anything fall into the pipe when you clean it.

The Check Engine Light may or may not be related to the gas cap warning. Only a scan will tell.

what did that message say?

Tester

That guy should have read his owners manual before making the video. It is not recommended to disconnect the battery, the manual states that the message will go away in a few days if there is no problem detected.

Also cycling the ignition will have no affect, the vehicle must be driven for the leak detection monitor to run.

1 Like

Thank you.