First off, I have only 1,615 miles on my car. About three weeks ago, I was
driving home and noticed my SES light was on. Took it in to Saturn the
next morning and waited for 2 1/2 hours while they checked my fuel
system. They ended up replacing the fuel cap. Everything was going fine
until this morning, when the SES light came on again. I'll be taking it
in to Saturn after work.

Is this a common problem? Will it be a chronic problem? The car has a
72,000 mile warranty, so I'm not worried about cost at this point, but I
don't have the time to take my car in again and again for the same
problem. Is there anything I can ask them to check so I can keep my
visits to a minimum?

Thanks for any advice you are able to give.

Do you know what code it was?
I got the SES lamp on my '01 lw300 at 42K miles with code P0495 (large leak,
evap canister). This is the same code you get when the gas cap is not on
tight. By process of elimination, found a defective canister vent solenoid.
$20 for me and free to you since you should be in warranty. Solenoid is
located right behind the fuel fill and is about a 1/2 hour job to change. no
problems since.

btw - hope that everybody knows that a flashing SES lamp means that there is
a potential for a fire. Steady on means that the car should be drivable but
needs checking soon.


"Silverrain" <silverrain_12000 (AT) nospam (DOT) yahoo.com> wrote

The code was P0492, I think. (A small leak.) It was at the fuel neck, and
they smoke tested it to make sure it was fixed.

The SES light isn't flashing, so it's okay to drive. I'll let everyone
know what they find tonight. Hopefully it's nothing big.

Thanks for your help so far.

Okay, took the car in yesterday and left it there so they could take their
time with it. They did another smoke test to find out if there was a leak
they may have missed the first time. No leak was found, so they called
Saturn's main technical service, and they told the dealership that it was
most likely a faulty sensor. They ordered the part and will call me when
it's in.

If this happens again, though, I'm going to be awfully upset. A car with
only 1,600 miles on it shouldn't be having problems like this.

The active parts that control that are the Purge solenoid (in the engine
compartment), the Vent solenoid (behind the fuel fill neck) and the canister
vacuum sense (on top of the fuel tank). The first two are fairly easy to get
to. The last requires half the exhaust system be removed and the tank
dropped out of the vehicle :-((

The evap canister test is done when the engine is hot (and a whole list of
other qualifiers). The normally open vent solenoid closes for duration of
test. The Purge solenoid opens fully (normally is modulating to get a small
flow). Tank vacuum sensor (similar to a MAP sensor) senses a vacuum in tank.
When a certain vacuum has been achieved, both vent and purge valves are
closed and the tank vacuum sensor monitors whether the vacuum is holding, is
a slow leak (P0492) or large leak (P0495).

To find my fault, I disconnected the valves and controlled them with
cheaters. Also added a 'T' fitting to the vapor line to monitor pressure
with a gauge. In my case the large leak was a sticking vent solenoid.


"Silverrain" <silverrain_12000 (AT) nospam (DOT) yahoo.com> wrote