For anyone who has the 1995 with cruse control and are showing a DTC 27 and DTC 28, you may want to read this.

Here was the problem when the light came on. The car would put itself into limp mode, kick on the fan, and the voltage would drop from 13.5 to 12.9.

So, i had the alternator checked, thinking it was a problem. And yes sorta, it was not charging the system very well, and also failed on diode ripple, showing AC voltage in the circuit. So next.... Alternator replaced with chrome 140 amp from www.alternatorparts.com (hey its on a show car, and the chrome looks sweet).

Put car back together, and still code 27 this time, and after driving for an hour 27 and 28 along with 32 which is EGR.

So next i pulled the solenoid's on quad driver 1 (code 27, qdm fault b) and tested the connectors. The specific solenoid's on a manual transmission car are, EGR, EVAP, MIL lamp. The mil was working, and its circuit tested out fine... HOWEVER, the EGR and EVAP pink wires were grounded out somewhere in the system, as they tested 12v to positive.

After days and days of endless sleep, the GM dealership suggested a bad PCM, so being a good little consumer i purchased one from my friend who works there for around $50, plugged it in and WAM same codes, same issue with the 12v on the pink with no fuse in the box..

Then it dawned on me, code 28 is cooling fan, air conditioning, and cruse control QDM. I removed the cooling fan relay, and still 27, ac relay, 27, cruse control connector to the module and ..... no 27 or 28.

So i'm not entirely sure, but i believe the problem to be in the power supply line to the cruise module or the module itself, but i just wanted to post this information since i couldn't find it anywhere else on the net.

For diagrams of the affected systems the dealership was kind enough to let me look through the service books and probably would let anyone one else having this issue. AND BTW the tech 1 scantool showed that EGR and EVAP solenoid's were grounded when we finally plugged it in with the cruse circuit plugged in.

Chris