Check Fuel cap light
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Laughing Gas
Joined: Nov 2014
Posts: 1,108
Likes: 23
Check Fuel cap light
As a first in Excursion ownership spanning 20 years, I had my check gas cap light come on. At first, I took it at face value and just replaced the gas cap. The light did not go off. I used a Foxwell Scan tool to read the code(That is in a whole new category of royally screwed up stuff-it doesn't know a 2003 Excursion exists and is essentially useless)It never worked-"could not communicate" (Gee my SCT programmer communicated) So after wasting a bunch of time, I broke out the laptop and the AE scanner. The code was something due to an incomplete scan(???) I reset it and it had been fine. Yesterday it returns. My laptop is in the shop with a bad power connector so I am left with only questions at the moment. It runs fine and the liemeter says I get better gas mileage..we'll see at next fill up. I've seen snippets of comments over time but I always seem to have something, even though mundane, which has some psycho twist. Is it the cap, something in the system or my scanner I purchased which is-lets say-not so good? Any ideas.
Hotshot
Joined: Jan 2004
Posts: 19,760
Likes: 1,079
From: St Louis
The "Check gas cap" message is set when the PCM has detected a re-fueling event and subsequently tries to bleed up vacuum in the fuel tank to check the integrity of the evaporative emissions system. The PCM commands the vent valve to close and the purge valve to open applying manifold vacuum to the tank. It then monitors the fuel tank pressure sensor for an increase in vacuum of a certain magnitude within a certain amount of time. The test fails if it doesn't detect this and the error is posted (assumes the cap was left of after refueling).
The same test is run periodically without regard to an immediately preceding fueling event. If that periodic test fails, then DTC P0455 (gross evap leak) would be posted.
Failure can be caused by anything that prevents the test from completing successfully
.
The same test is run periodically without regard to an immediately preceding fueling event. If that periodic test fails, then DTC P0455 (gross evap leak) would be posted.
Failure can be caused by anything that prevents the test from completing successfully
.
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