dapsaute

I have a stock 1995 Z28 with 47,600 miles, 4L60E, 3.23 rear. I got it a few weeks back and did the usual PM...oil/filter, fuel filter, ATF swap, and had my mechanic go over it a couple of weeks ago. Drove it Friday and this Wednesday, not problems at all. I've put about 300 miles on with no issues other than the AC, which is fixed and blowing Icy cold.

Last Friday, about 120 miles ago, I put a fresh tank (fresh tank #2 of same fuel) of Amoco Ultimate and Lucas Fuel System Cleaner. Ran really well.

This morning, on the highway at 1800-1900 RPM, SES light comes on..stays on, does not flash.

Oil good at about 40PSI, no apparent leaks on garage floor, just changed 300 miles ago or so.

Volts good

Coolant good

Not wanting to push my luck, but there is no apparent misfire...runs as it did a couple of days ago.

Really, the only difference...other than the light, is that tonight I wanted to take it to Cruise Night.

I'm hoping this is an Emissions BS problem.

Has anyone else experienced this?

Does anyone have a scan tool...preferrably not $500...that they would recommend? I would like to diagnose it myself, but if I have to got to my mechanic, so be it.

Any thoughts?

Thanks,
Dave