I’ve been getting the Fuel Tank Cap Loose or Missing message on My 2005 Land Rover LR3. This message has persisted and turned into a check engine light, so it’s time to fix it!
The loose or missing gas cap message means that the vehicle thinks there is a leak in the evaporative emission control system, or EVAP system. This is the system that controls the release of fuel vapors into the environment. The typical cause for a leak in the EVAP system is a loose, missing or faulty gas cap. Many times you simply didn’t tighten the cap enough or forgot to put it back on. If the message persists, you probably have a bad gas cap. There is a seal and other internal things in the cap that eventually wear out and the the cap will need to be replaced.
This is the genuine Land Rover gas cap i installed on my LR3: http://amzn.to/2gyADnF
You do not need a genuine gas cap, you can buy other brands: http://amzn.to/2yHoqoQ Make sure the fuel cap fits your make and model of car!
The bad gas cap may cause a check engine light. After you replace the cap you can clear the code with an OBDII reader or disconnect the car’s battery for 30 minutes. When you reconnect the battery the check engine light should be gone. You can also just drive the car until the car realizes there is no longer a leak and the code should clear on its own. If the check engine light with fuel cap loose or missing message returns, then you may have a leak elsewhere in the EVAP system. IF you are not familiar with the EVAP system components, it may be wise to have a mechanic check for leaks in the EVAP system as there are a few key items that they will know what to look for on your car.