My CEL is on. A code reader at a gas station could not see any code. Is it possible that the light can come on without a code? Also chipmunks got into my air filter box so I cleaned it. Maybe this is related. Anything else they might have clogged up? Thanks, I will be working on this tomorrow with my own code scanner. Can the turbo somehow get clogged by chipmunks? Also I am losing coolant very slowly - maybe one cup per month, Is that clue? Autozone is not loaning pressure testers currently - do people make there own?
Just wondering - does the light ever come on simply because a mileage interval elapses to induce owners to go to Volvo? Also the car feels a bit sluggish.

The CEL is only turned on when an error is found. Autozone should have been able to tell you which codes are active.

The message center will tell you when you need service, based on miles and usage.

Chipmunks also chew wires. No, they will not get into the turbo. How in the heck did they get into the airbox? If they chewed through the air intake hose, that will be the cause of the CEL.

Losing coolant: check the hose from the coolant bottle to the engine for leaks. Also check the passenger side of the radiator for leaks. Use a clean paper towel to wipe the areas after the engine has heated up and is turned off (maximum pressure).

If it is a head gasket, a compression test will let you know.

Your car is also old enough to start having heater core issues.
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Keeping it running is better than buying new