That's interesting. On ours the check engine light started being tempermental about a week or so before christmas. What I started noticing is that it would turn on when turning the car on in cold damp weather (drizzly) but even the car was indoors (garage). We've known about the gas cap and were always concienscious about it and didn't have problems for 1.5yrs. By the time I took the car in after I realized it wasn't the cap, checked it, filled up the tank, etc. I took it in and that morning it turned off. No codes were stored in the computer so they couldn't trouble shoot it.

Last night it turned on again and fortunately it stayed on this morning, after two restarts so I drove straight to the dealership where I left it on and they hooked it up. ECM-16 which is a the O2 sensor. So it's faulty! I'm getting it replaced Friday. I'm exited that there was a real fault and not an annoyance.

So a question is... how long does a code stay in memory? What event causes it to be purged?

Alberto

I had a similar problem in my 2000 V40.

Turns out there was a bad check valve in the gas tank
vapor recovery system. The symptoms are similar. This
can also be caused by a loose cap.

The problem has not recurred in my circumstance.

However, if the code read by the dealer is indeed poor
gas quality, then you might have some other problem, indeed
related to the fuel. I'd ask if they're sure about the code,
and for them to check that it is indeed a bad fuel code or
the bad fuel evaporative recovery system code.

Good luck.

I'm not certain this is your problem, but it sounds like you are expierencing the same check engine light problem as I did. Volvo says the electrical fuel vapor valve depends on gravity to close and is getting stuck. They replaced mine with a spring-loaded valve in my '00 V-40.

-Don M.
'00 V-40, silver, practical.
'93 RX-7 TT, silver, faster.
'98 Ducati 900SSFE, silver, quicker.

Repost and tell us what fault code they came up with. Fuel quality code? Never heard of that one. Sounds like a line of crap. If it was bad gas, it would also affect performance.

If that's what's showing up (likely, common) it has nothing to do with fuel quality. There's info in a SB in VEN (Volvos intranet SB source) where the cure for that code's listed, gets a new check valve.

Another known code related issue for S/V 40s is cured by a software upgrade through their Vadis cart (typically ECM 13)

I've NEVER heard of a code for bad fuel quality. Suggest that an experienced Volvo tech, not a rookie looks at your car next time.