Intermittent SES light

[BlankMan]

For a few weeks now my check engine light has come on for a few days, then off for a few days only to come back on for a few days - it's a repetitive cycle. Last week I figured out the pattern. If I have a full tank of gas, the light is off. It stays off till around 220-240 miles with about 1/4 tank showing on the gauge. Then it comes on. It will stay on until I fill the tank. Doesn't matter if I fill it right away or wait until the fuel light comes on. After filling the tank, it goes always turns off within 20-50 miles and stays off until I hit around the 1/4 tank level again.

I'm setting up a time to take my car in to have the codes checked, etc. But unitl then - anyone know what could be the cause of this? I'm guessing poor fuel delivery when my tank falls below a certain level (around 1/4), maybe causing a lean burn? faulty fuel pump could be the culprit? I had both the up and down stream O2 sensors replaced a couple months back when it was doing the same thing. Looking for thoughts. Thanks.

J

[Fishboy55]

This is just an off guess, but if you pull the code and it says its a P0455 Evaporative Emission Control System Leak Detected (gross leak) I know what it is. I had the same symptoms. Turned out there's a pump that pressurizes your fuel tank as part of the emissions control. If the pump can't pressurize the tank it throws a code. The times it tries to pressurize is very random, which is why the light is intermittent. My fix turned out to be a vacuum hose on the pump that wasn't holding up under the pressure. Also check and make sure your gas cap is on tight, until it clicks. That's also part of the same system.

Chip