[KAHruzer]

It means a blink Code is being displayed on the ECU. It's under the passenger seat.

 

[KAHruzer]

Code 12 = Exhaust Gas Recirculation System, probably the EGR Valve, but could be as simple as a vacuum leak in a tube. There's a 12-page diagnostic in the manual.

 

[KAHruzer]

There's a sketch type diagram of the thing in the manual where the code diagnostic is located. Could be easy enough to patch together a simple version of same. (11-30 in '88 Coupe OEM Manual).

Or, you could just nic the wire insulation for meter test probes, then tape over later.