Thank you for the input Sven. I went out Monday and checked all the grounds and they are all good.

It occured to me that the Cranshaft Position Sensor (CKP) plugs directly into the ICM so I picked one up at NAPA for $20.99 on a chance guess. When I got home Monday I looked into which code a CKP would generate and there isn't one! As it turns out, in the 1989 1990 1991 1992 and 1993 Pontiac Grand Prix, code 42 is listed as "Ignition Control (IC) Circuit" which contains the Cranshaft Position Sensor.

I put in a new CKP and the code 42 went away.