2002 Chevy Blazer Check Engine Light

Electrical problem
2002 Chevy Blazer 6 cyl Four Wheel Drive Automatic 70.000 miles

Hi - The Check Engine Light was intermittent for a while but now is on all of the time. I checked with a generic OBD2 code reader and got a 'Fault 01' indication. I realize this may not be a common fault code for the OBD2 code reader but this is all I get. The engine and everything that I can see is operating normally.

Now the first time it came on was when I was coming down a steep grade (Wolf Creek Pass) and dropped it into 3rd and 2nd to slow the vehicle down. And then when I would put it into drive, the light would immediately go out, and come back on after 3 to 4 seconds when I dropped it back into 3rd. Then after 3 or 4 days the light came on and stays on (with the engine running). The vehicle is at 7,000 to 8,000 feet altitude.

The engine is a 4.3 Vin W.

Donation well depend on results - is this okay? I hope so.

Any ideas or help.

Thanks,

Bob Lowe in Colorado