I've read quite a few posts about the Check Engine light, but I'll put this question out there anyway. I just bought a used 98 S70. About a week after buying it, I refueled with the engine still running (yes, I read later that that can cause the CE lamp to turn on, but up here in NH it was COLD). Anyway, I filled up, and drove to work. Later that day I headed home, making a few stops along the way. Later that evening I went out again, and then the CE lamp went on (had driven about a 100 miles since refueling). If refueling with the engine running can cause the CE lamp to come on, I would of expected it to happen immediately. Is it likely that refueling with the engine running did cause the problem (but then why did it take a while for it to come on?) or is it likely something else?

I also read that after driving a while (starting / stopping the engine) the light will reset itself if the problem no longer exists. Any ideas on how many start / stop cycles it takes to clear the lamp?

thanks

I have a 1999 S70 AWD with 55,000 miles. The check engine light has come off/on many, many times throughout the life of the car. I've spoken to Volvo dealerships and independents. 99% of the time the light is due to the gas cap, not just filing up with the engine running. You see, the gas caps/filler nozziles are all, basically, defective. They must be VERY carefully screwed in every time (Volvo has never issued a recall). The slightest mistake will cause the light to come on. Usually, it will go off after 200-300 miles. If I could, I'd disconnect the light, but Volvo refuses to do it. My best suggestion is go to Volvo ONLY if it keeps going off/on for a long period. Out of warranty, you will go broke paying Volvo to "check the codes" only to tell you it is the gas cap. The only reason this light comes on is for an emissions problem. You can safely drive the car with the light on. Hope this helps.
PS: A word to the wise - At full service gas stations, always screw the cap on yourself., if not, you'll be looking at a check engine light for another 300 miles. I love my Volvo, but welcome to the world of European cars. This kind of stuff "just happens" with these cars.

I have a different experience with the CE light. Mine kept coming on every couple of months and staying on (I have a '98 and the logic for turning off the CEL is different in '99 than it is in '98 cars). The first few times the dealer gave me the gas cap explanation. Even replaced mine with the "older" style from an 850. No help. CEL kept coming on as before. The dealer then started replacing parts (under warranty). Charcoal canisters, check valves, rollover valves, you name it, I have had at least two replaced. No difference in CEL behaviour. I got fed up and wrote a letter to the service manager, who got personally involved and finally, started to work the problem, instead of blindly replacing parts. The whole time the codes that were stored were 611 and 612, which are fine and gross vapor leak in the vapor recovery system - classic "gas cap" codes. To make a long story even longer, they have determined that my gas tank was defective. After ordering a new gas tank, they figured out that the superceded gas tank (new design) did not fit, so they had to locate an old-style new tank. When that arrived it turned out that my original tank was missing some sort of restricter, a tiny nylon washer-like part that sits in one of the numerous hoses coming out of that gas tank. Put that restrictor in and... It's been just over a year now with no "gas cap" CEL. So, the moral of the story is that the gas caps maybe just fine in these cars and the problem is elsewhere, like a missing restrictor in the gas tank. But, since the codes that the ECU throws are the ones that suggest the gas caps, most dealers just blame the operator.

I did end up buying an OBD-II scanner though to be able to clear the CEL so I can pass inspection once my car is out of warranty and all the CEL episodes are on my nickel.

Good luck.
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Vladimir. 1998 S70. Base, 5-speed manual.

The Chiltons I just bought confirmed that the:
"Malfunction Indicator Light will/may be deactivated for some codes if the vehicle completes three consecutive trips without a fault detected with vehicle conditions similar to those present during the fault."

I think it's three driving cycles for it to clear. Also possibly some diagnostics are only run after 30 seconds of idling, so the light wouldn't be immediate. Usually you will see it pop up while waiting at a light. I don't know about actual codes vs pending codes, that a code could be pending without lighting the lamp. But I am not a tech, just learning these things from here and other sources...

- Tom E
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98 V70 GLT black 54k

I am not sure about the check engine light. Just feel the need to chide you a bit. In the state just to your east there are signs at the gas stations and stickers on the pumps. Right below "No Smoking" it says "Turn off Engine". Be fair to the other users of the facility and to your family. Turn it off.

I don't think that the "CHECK ENGINE" light on the '98 S70's will clear without being electronically reset with a diagnostics tool.

chads

'98 S70 (all stock) and '89 740 (true BRICK!)

FYI - the Check Engine lamp did go off on its own after 15 start / stop cycles over 3 days.