We have the same car - 2006 w/ L4 - and engine light problem. My mechanic has tried several times to repair and couldn't - then took to to the Pontiac dealer & still no repair.
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I took my car to the garage to have front wheel bearings replaced and check why the "check engine" light was on...Since my car was running perfectly, I thought maybe due to hitting 60k that it wanted routine maintenance.
Garage said my computer "quit communicating" so he re-programmed it. Since picking it up, my mileage and power are both down 25%...then the engine light went back on. Took it back, he reset it and cleaned the fuel line (rail?). But, same problem w/ mileage & power.
I have a 2006 G6 w/ 4 cylinder... used to get up to 34 @ 65mph down a flat highway and 26 mixed driving. Now 18 mpg in mixed driving.
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I took my car to the garage to have front wheel bearings replaced and check why the "check engine" light was on...Since my car was running perfectly, I thought maybe due to hitting 60k that it wanted routine maintenance.
Garage said my computer "quit communicating" so he re-programmed it. Since picking it up, my mileage and power are both down 25%...then the engine light went back on. Took it back, he reset it and cleaned the fuel line (rail?). But, same problem w/ mileage & power.
I have a 2006 G6 w/ 4 cylinder... used to get up to 34 @ 65mph down a flat highway and 26 mixed driving. Now 18 mpg in mixed driving.