My 98 V6 is giving me the P0440 code. I've replaced the gas cap and it still comes on. Usually when the gas level gets low.


Any ideas?

Is the gas gauge reading correctly?

I had a fuel sending unit go out, and when the gas level got around 1/4
of a tank the gauge would intermittently show that it was empty.

However, I don't know if the fuel sending unit would give the code that you are seeing

The gas guage is working fine. Gas mileage is the same. There's no smell of gas in the garage.Starts/idles/drives fine.

From what I have seen, these codes are fairly universal. Below is a link to a discussion about this code on another car:

http://www.discoweb.org/forums/showthread.php?t=9464

I hope that it helps you out.

Causes of a P0440</span> code may be as simple
as a loose gas cap or filling up with the vehicle running but can also be caused by a bad fuel tank pressure
sensor or malfunctioning vapor canister. There is a purge solenoid and
valve in the vapor canister that can fail preventing the fuel tank from
maintaining pressure.

Is the vapor cannister on the driver's fender well next to the air filter? If it is the check valve in it is working.


I often fill up with the car running, but never had a problem before...I'll try turning it off.

There should be a canister (kind of rectange shaped) above and behind the rear axle. Will be between the rear axle and spare tire if you have undercarriage spare.

One of the guys on another forum that was getting this code found that canister to be cracked. Replaced it with a salvage unit and all is fine again.

Couldn't find a crack in the canister. There is no "woosh" when I remove the new gas cap (wasn't with the old either). Got inspected last week and the Evap rediness code was not set to ready (but I still passed). I drove to the beach this weekend and the CEL has not come back on. But I did expect better gas mileage on the highway (got 18 mpg).

you should get the system psi checked at a shop that has the right equipment.if the light comes on this many times you definatly have an open in the system.sometimes squirrels can get above the tank an chew on some evap lines.or you may have a small rust hole in the filler neck.look closely for stains around the filler neck.also if you have any recent work done underneath the hood make sure the evap line are not crossed at the purge solenoid.the solenoid is labled to identify which hose belongs where.even the seal around the fuel pump can leak.that is the next common thing next to the gas cap not sealing.if you have a aftermarket stant fuel cap get the o.e. one.follow the lines from purge solenoid to the tank an to the vent solenoid an canister you may see somthing obvious.if not psi an smoke checking the system is the best way to find small leaks.