SES oddity

I have a history of my gas cap sealing poorly, and setting an SES code. When I had my LS1M I'd just clean the sealing surface for the cap, then clear the code and it stayed off for months. Last summer I sold the LS1M, then got the SES light again in the fall. Drove it all winter with the SES light on. Today, there's no light. Isn't that real odd? I've been planning to pick up a cheaper code reader, just haven't gotten around to it. Now after 5 months, the SES light goes away. Anyone experience this before?

I am going to replace the gas filler neck this spring, so it shouldn't be a problem anymore, but the light disappearing after being on so long seems real unusual.

Not such an oddity. The EVAP system is picky as hell. The rubber seal on your gas cap was probably "shrunk" due to the cold weather, hence allowing the .04 inHg leak to be detected and the SES light being on. When it warms up, the seal "expands" temporarily stopping the leak. If your filler neck isn't rusty, I wouldn't replace it. Just get a new gas cap and see what happens.

I replaced the gas cap & gasket about 2 yrs ago. Had no issues with it sealing last winter, no SES lights.

The filler neck, esp the gasket sealing surface, is badly corroded. I sanded it down last summer as a temp solution. This spring it gets replaced. I've never experienced an SES light being on for such an extended time period, 5 months + then going away on its own. I thought all SES codes had to be cleared before the light would turn off. That's been my personal experience.

1998 Riv wrote:

I replaced the gas cap & gasket about 2 yrs ago. Had no issues with it sealing last winter, no SES lights.

The filler neck, esp the gasket sealing surface, is badly corroded. I sanded it down last summer as a temp solution. This spring it gets replaced. I've never experienced an SES light being on for such an extended time period, 5 months + then going away on its own. I thought all SES codes had to be cleared before the light would turn off. That's been my personal experience.

Good idea, replace the neck.....

Nope! SES lights will go off on their own after a set amount of drive cycles with no fault. EVAP is a perfect example of this. One time your driving and it detects a fault...BAM...engine light. 3 days later after 10 drive cycles or so, it goes off because it detects no more faults. However, certain "conditions" must be met in order for the PCM to run an EVAP system test. It very well may be 5 months or so before these tests are run depending on your driving habits......it runs a component test on initial key on, but the "leak" test needs the "conditions".

Just for shiggles, loosen your gas cap and drive around until the SES light comes back on (this wont hurt a thing). Shut the car off, tighten the cap, and see how long it takes for the light to go out......

No thanks, the light's been bugging me since last fall, I think I'll leave it for now.

1998 Riv wrote:

No thanks, the light's been bugging me since last fall, I think I'll leave it for now.

Bad SES light!

You can also clear the light if it bothers you by disconnecting the battery for ~20 minutes i believe.

Guess it didn't bother me that much either...