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Check Gas Cap Light On on 2002 Ford Taurus

Just today I noticed an indicator showing up on my dashboard. The indicator shows the passenger side of the car, and a little screw coming out of it. I grabbed the giant book of boredom (Car manual) and the indicator is one for checking the gas cap and says once the gas cap is seated properly the light will go out.

I reseated the gas cap making sure it clicked when I turned it, and drove the car for about 45 minutes (My drive back home), and the light has continued to stay lit. What seems strange is that the check engine light is not showing up, which I know typically happens if the gas cap is not on properly.

Is there a sensor somewhere in the car that will cause that ‘check gas cap’ light to come on, and if so is it something I could find and replace myself, or am I better off going to a shop?

One would imagine that, if it were related to any evaporation control, your check engine light would be on as well.
Since gas caps tend to be cheap, I’d replace the cap to see whether that fixes it before you bring it into a shop as that’s what they’ll likely try and charge you for it.

It is very possible that you need to go through several “driving cycles” in order for this warning light to turn itself off. A driving cycle consists of starting the engine and then driving x (I don’t recall the exact number) miles before shutting off the engine. In other words, one 45 minute drive is unlikely to turn it off, even if the problem has been corrected.

I suggest that you go through at least 5 drive cycles before you conclude that anything is wrong. If, after 5 drive cycles, the light is still glowing, then I would suggest that you do as Remco suggested, and simply buy a new cap–preferably one from a Ford dealer’s parts dept.

Those drive cycles somehow recalibrate the system, then?

Goes to show you that one learn something every day.

Remove the gas cap and take a close look at the plastic filler neck to see if it’s cracked. I just had a Sable come in for the same problem and it was caused from a cracked filler neck.


The driving cycles do not recalibrate the system, some have a minimum number of cycles or runs without the sensor sending an alert before the light turns off.

Check your owner’s manual to see if there is a way to reset the indicator like you would with a tire pressure monitoring system. I wouldn’t wait to replace the gas cap. They’re relatively cheap, and it doesn’t hurt to have a spare gas cap in the trunk.

Small evap leaks trigger the gas cap warning on cars that use the differentiator lamp (check gas cap) because it is a common failure mode. This reduces people having to come in for repair only to find out their gas cap is loose or leaking. So the CEL is not lit for small evap leaks when there is a CGC lamp.

Just like it takes several drive cycles to extinguish the diagnostic lamp, it will not illuminate unless the condition exists for several drive cycles to avoid false positive indications. Resetting the lamp by clearing codes or disconnecting the battery will not help and may only cause more grief when all of the other monitors also get reset.

Remove the gas cap and carefully examine the filler neck. Feel it with your finger nail. It should be baby skin smooth. Same for the mating gasket on the cap. Dirt on either mating surface, rust, pitting, cracking, hard gasket on the cap due to aging all will allow vapor to escape and set off the diagnostic indicator. If it seems OK, you can try generously applying some vaseline to the mating surface. If the lamp goes out after 5 drive cycles, it is likely the cap or neck. If not, there are other sources for small evap leaks…