Andy, I posted this on another board but I thought you would give you some hope that there is light at the end of the tunnel (and I'm not talking about a train) Copied from a post on Freel2 My neighbor drives a Toyota Pickup His truck is >100,000 miles and a 2006 model year Check engine light is on ...

He suggested simply using a bottle of CataClean to see if that helps. Thoughts? It can't hurt and it is possible there is crud from the misfiring causing the P0420. If you do this, read the instructions on the bottle, do the math and get the mix ratio correct. I suggest taking it out on the Interst...

Andy, I have two things to add. Some codes point to exact parts that are the problem. P0420 isn't one of these. Good news is we have a deep collective knowledge of P0420, lots of experiences here with that. The O2 sensors are the downstream culprit with this code and the code's description mentions ...

Andy: To sum up your shop's latest advice - "the parts are so powerful the system cannot handle it." First - why did they put them in and if this is the case they should take them out and replace with Volvo OEM. Continuing on this lunacy, the coils are designed for the car and should be ex...

Andy, For my 2010 S80 3.2 the Thermostat failed but I had no symptoms. I replaced it only because it was known to fail for others. The post that convinced me that being proactive with the change can be found here (This is the post with the ignition coil failures) http://www.volvoxc.com/forums/showth...

Stay away from that shop, they ripped you off BIG time. For the 6-cyl engine, even 6 spark plugs and 6 coils do NOT cost more than $300! For example (rmeuropean.com): - Volvo Ignition Coil $70/each. - Bremi Ignition Coil $36/each. You need to find an independent and honest shop that knows something...