Service engine light and O2 sensor

I have a 1995 (door tag says manufature date of 10/04) Aurora with 160000 miles on it. The SEL comes on after the car is warmed up to 200 degrees on the temp gauge. If I am going slow (10 mph) and push the gas down, say 1 inch, the light will go off for a tenth off a second when the pedel is let up. The car will also jerk and shutter 2 or 3 times at highway speed just before the light comes on. After the light is on the car runs fine but does seem to lack some power, it is just sluggish. If I let the car sit for a few hours the light does not come on until the engine warms up again. I am thinkiing this could be a bad O2 sensor. I took it to a few parts stores but they were unable to scan the computer, the scanner says that the car is not responding.
I know the O2 sensors don't work until they are heated up to 600 degrees or so and I would think if it was broke it would run in some default mode. Also if I shut the car off for a short period (not enough to cool down) and go to start it, it takes more cranking time to start the engine and I have to step on the gas pedel a little to get it to fire up. Does anyone have have ideas on what could be wrong and who can scan these hybrid OBD other than the stealer.
Thanks
Dave A.

I have a 1995 (door tag says manufature date of 10/04) Aurora with 160000 miles on it. The SEL comes on after the car is warmed up to 200 degrees on the temp gauge. If I am going slow (10 mph) and push the gas down, say 1 inch, the light will go off for a tenth off a second when the pedel is let up. The car will also jerk and shutter 2 or 3 times at highway speed just before the light comes on. After the light is on the car runs fine but does seem to lack some power, it is just sluggish. If I let the car sit for a few hours the light does not come on until the engine warms up again. I am thinkiing this could be a bad O2 sensor. I took it to a few parts stores but they were unable to scan the computer, the scanner says that the car is not responding.
I know the O2 sensors don't work until they are heated up to 600 degrees or so and I would think if it was broke it would run in some default mode. Also if I shut the car off for a short period (not enough to cool down) and go to start it, it takes more cranking time to start the engine and I have to step on the gas pedel a little to get it to fire up. Does anyone have have ideas on what could be wrong and who can scan these hybrid OBD other than the stealer.
Thanks
Dave A.

http://www.troublecodes.net/GM/
For some info on it.
Some 94-95-96 You need a high end scanner with special adapter to check codes.
A good repair shop or dealer can take care of ckecking codes and a scanner read out.
Theyl just charge 1/2 hr to a hr diagnostic time.
If you get codes poat back code no.