I bought a 2000 Pontiac Grand Prix GTP last night. It was quite a drive home. On the trip the speedometer needle was sticking so I tapped on it and the check engine light came on. The next morning I went to the parts store and it gave me three codes p0404 (EGR) p0137 (o2?) and p0650 (light control circuit). I erased the codes and drove the car all day and no engine light came back on. The code I am concerned with is p0650. The SRS airbag light comes on and off randomly in the cluster. Also, the low fuel light comes on but it is at 1/4 tank. The tachometer is at 3000 RPM at 70 mph (which seems high to me) but the car sounds fine. It doesn't sound out of gear or not in overdrive. Also, the traction control button does not function and the Driver's center blinks 0's when you get on the gas hard at times. It is getting 23 mpg highway (which it should be around 28.) It does need tuneup and there may be vaccum leak--and EGR and o2 censor. Could these symptoms keep the car from shifting to overdrive? Odometer reads 122xxx miles. It wasn't doing these things when I was testing it--they started about 100 miles after I left. The car ran for about half hour in the parking lot while we were discussing and I drove it for about 30 minutes before that.
The code p0650 and the fact that I tapped on the cluster and the light went off and the other issues with the cluster leads me to believe I have a bad cluster.
However, after reading online some more and seeing some other cars/symptoms I wonder if I have a bad pcm or tcm--given the fact that the car at highway speed is about 1000 rpm's higher than it should be and the traction control button doesn't work on the dash and that it is only getting 23mpg highway. Or could my rpm's and poor gas milage have to do with egr valve and o2 censor and needing tuneup?
Some backstory:
I had a 99 GTP for 9 years so I know how they are supposed to run normally. It was having issues with shifting and rpm's dancing. The Transmission tech said he couldn't tell if it was transmission until I addressed other symptoms first. It had new plugs and wires. I put the cat back on and put on a new EGR valve and it ran better and the the gas mileage went up, but it still rpm danced from time to time and it would not shift to overdrive somethimes. I just sold it because it was getting old and had a bunch of other work needed I was ready for some different colors.
Basically, with the one I just bought, I am not sure where to start. Could this p0650 be connected to a pcm or tcm? could it be connected to overdrive and poor gas mileage? Could it be a bad cluster (if I could only be so lucky). Probably start with tuneup tomorrow and replacing vaccuum lines (there is a his when the boost kicks in from the supercharger). The vaccum lines are so flimsy on these cars. I fought that for years with the 99.
Thanks.
