The check engine light is on in my T5. Can I do anything about it or do I need to take it to the dealer? It runs fine and has about 157K.
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Leon Ramseur, Gastonia, NC, 2008 XC90, 2001 V70T5. 1993 940 Wagon.

Went to Advance Auto and used their OBDII reader. It cleared the code and the light. After restarting about 10 times, the check engine light is still out so, I hope, everything is OK. Thanks for every bodies help.
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Leon Ramseur, Gastonia, NC, 2008 XC90. 2001 V70T5. 1993 940 Wagon.

The light came on again and gave a P0422 code, "Main Catalyst Below Threshold (Bank 1)". What do I do now? Would running regular gas, which I have done for the last 2 tank fulls, instead of premium in a turbo cause this?
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Leon Ramseur, Gastonia, NC, 2008 XC90. 2001 V70T5. 1993 940 Wagon.

That message means that the O2 sensors, front and rear, cannot confirm clean burning engine.
Most shops will tell you that your Cat is distroyed and you will need two O2 sensors to boot!

I say use minimum 89 octane. If you currently use regular, fill the tank with premium to bring the tank up to 89 octane. The use of 87octane will cause the engine to knock; the knock sensors will inform the ECU/ECM and your timing will be retarded and additional fuel will be used to cool the piston chambers to stop the knocking.
This additional fuel is probably not burned completely and winds up in the cat. Too much of a bad thing is not good for your car.
If you look at the price of gasoline, 89 octane is 10 cents/gallon more than 87 octane, and 91/92/93 octane is 20 cents more than "regular". After you fill an empty tank with 18 gallons of fuel, multiply the 18 gallons by 10 or 20 and calculate how much more good gasoline costs compared to junky regular : $1.80 or $3.60 - per tankful! Whoopdeedo. One cup of Starbuck's coffee!!!

Klaus
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I still miss my 164 and my 854T. Just driving a V70R :)

I'll stick with premium gas from now on. I have learned my lesson well!
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Leon Ramseur, Gastonia, NC, 2008 XC90. 2001 V70T5. 1993 940 Wagon.

If you're in this for the long term you might be able to justify buying an OBDII code reader, the low end of which starts in the $50 to $100 range. All cars starting in 1996 have OBDII readers within 3 feet of the driver's seat, usually under the dash. Available at just about any retail auto parts store, Sears, Wal-Mart, eBay, just about anywhere.

Take it to an autoparts store and get the codes read, free. They may not reset the codes, but usually do if you beg.
Write down the codes and figure out what is wrong, we can help when you have them in hand.

Klaus
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I still miss my 164 and my 854T. Just driving a V70R :)