Purchased a 2004 Olds Silhouette last month with 110,000 miles on the clock. One-owner. Extremely well-maintained according to the Carfax. The guy had it in every 3,000 miles for service and had the tranny flushed at 50,000 and 100,000. On the Carfax, however, starting at around 90,000 and continuing until I bought it, were numerous "Check Powertrain Control Module" entries. I was a bit concerned at that, but I bought the vehicle anyway. Now I know what it meant.

Although the vehicle runs generally flawlessly, the "Check Engine" light is baffling numerous mechanics. The dealer I bought it from said the code read "O2 sensor," so they replaced it. Light came back on for me. Took it back to the dealer. "O2 sensor" again. Replaced ALL O2 sensors. Light came back. Took it back. Dealer got the "O2" code again but this time read further into the codes. Something about a PCV valve came up. Dealer found a tiny leak. Fixed it. Drove a bit. Light back on again. Dealer threw his hands up and said to find another mechanic, preferably a GM mechanic, and see if they can figure it out. Took to GM dealer. "O2" code again. Replaced oxygen sensors again. Light just came back on.

Now I know why the guy before me had it checked a zillion times, because it must have been doing this to him for the last 20,000 miles, too, and several dealers cannot figure it out. Anyone?????

I once had a girlfriend who was persistent......whatever she saw in me, I'll never know....

O2 code means nothing....we need the specific code....makes you wonder why both sensors were replaced.......

Shame on the GM dealer, replacing them again......they have this wonderful tool, called "MOI".......they have the ability to take a snapshot of this while it'* happening, and a good tech should be able to interpret the data to make a sound diagnosis, especially after knowing the history of the vehicle......

A bad MAF can skew O2 data........but I digress.....once again, shame on you GM garage, the gauntlet was dropped, and you didn't pick it up....

Wait one minute!! The dealer actually said that? Never take it there again. Morons! As mentioned what are the codes that are current as of now.

dont take it back either of those places they dont know what they are doing. as mentioned there are a number of o2 codes and they they tell you what is going on with the engine not that they are bad. you can go by a parts store and have them read and post the specific number here