Last week the disco threw P0455, the mass evap leak code. I checked the gas cap and sure enough, the wife didn't fully screw it down when she got gas the night before... so I tightened it down properly until it clicked, cleared the code, and on we went.

Then today the code reappeared.

I went back and checked the gas cap again, mind you, I was the one this time who last closed it... and sure enough! It was almost completely unscrewed just like before. What the heck is happening? Is it possible for the gas cap to become unscrewed and basically thread itself off?

We have a spare gas cap from a donor disco, so I'll swap that on and see if it helps. Weird though...

 

The cap needs to "click" at least 3 times.

I've had this happen a few times with LR's & other cars...especially Honda!
In my experience 9 out of 10 times the ratchet mech in the cap was bad.
Grab a new fuel cap and you should be good to go.

 

I've only seen something like this happen on a Abbot and Costello movie...sorry...that's all l've got...lol.

Brian.

 

It also could have been cross threaded in and vibrated loose.

 

I replied in your other thread but here it is again. Might also be your problem. My cap seemed to swell in the heat of the day then contract when it got cooler in the evening etc. What feels fully screwed in when hot will be loose when cold.

I got a new cap for 5 bucks on Amazon and problem is gone

 

I just get the 5.44 STANT gas cap at Wal-Mart, take it apart, use the newer threaded piece, and all internal parts, and then re-use my original cap with the lanyard on it. I've seen the threaded parts of the filler neck get nasty causing the cap to click prematurely. If you look from the underside you'll see the gasket isn't seated against the filler neck. Either use some scotchbrite pads on the threaded filler neck, or replace the gas cap.

 

Here in Oregon they pump your gas (totally stupid), I usually tighten my own cap on the Rover because they (the fuel jockeys) can't seem to tighten it correctly to where it seats. I cut off the lanyard to make it easier for them, cleaned the threads, but it's still difficult I guess.... I may just break down and buy a new cap so I don't have worry about telling someone they might be too stupid to correctly tighten down my gas cap....lol

 

You said "I cleared the code" You did not explain "How" you just cleared the code.
How do you clear just one code? Do you mean you unhooked the battery and cleared ALL codes? How do you clear just the gas cap code?

Mine was on but its a P0442 on a LR3 for the gas cap. I tightened the cap and the code is still on. I doubt they instantly clear even with a new gas cap. Not sure how to clear just the check engine light and the code thats causing it.

 

I had this exact same problem with the original Land Rover gas cap. I was constantly getting an Evap code.

Buy a locking gas cap. If you are really brave get one with a key and make lots of copies. It's a bit of a hiccup because you have to unlock-lock your gas cap. It's a bitch to it get off if you forget the key. I got 4 copies. 2 keychains , 1 hidden in car, 1 in the house.

Some drug addict homeless guy, asked me the car had the catylitic converter on it. I figured why not just cut off the cats .. sell them (I got $$$$ USD for OME Rover Cats) and replace with a cheapo.

And since they are stealing cats why not replace the gas cap with a lock. I stopped getting the evap codes after that.

 

Rajod, you clear codes with a scan tool plugged into the OBD2 port. I don’t think disconnecting the battery will clear it.