Aviator857

I have a 89 firebird with a full swap from a 2k formula. So its the 5.7 LS1 with a T56. I have the pedal assembly from the 2k in the 89 with all the switches etc. I built the wiring harness from the 2k and a second 2k harness to extend it so I could put the PCM under the dash with proper wire colors. The PCM, pedal, trans, engine, gas tank, pump, cruise module, and even the emissions are all from the same donor car. It had a kills vin title so I was never able to test the cruise control before I dissembled it but everything else worked on the car. The car was a non traction control car and drive by cable.

Here is the issue I can not get the cruise control to engage. In HP Tuners the Cruise Lockout never goes to "no" even if I go to special functions and set cruise inhibit to no in hp tuners. (not sure if the two are directly related or not). I picked up a used GM cruise test module and it shows the cruise module as functioning. It also shows the brake and clutch as well as the cruise on,accel,set buttons function as expected (used it to verify that my wiring was correct). I installed a 2000 1500 (truck) cruise module and it works as the truck modules don't use the inhibit wire. With the truck module if I set cruise the cruise status in the PCM properly sees the cruise active signal and shows that in hptuners. Since the truck module works I'm sure i have the clutch/brake/switches wired right. I even tried a second fbody module.

Obviously I could just use the truck module and be happy but the fact the pcm isn't setting the cruise prohibit flag right makes me think I missed something in my wiring.

So... what parameters must be met in the PCM for it to turn "Cruise Lockout" from yes to no?

The only thing I can think of is on the PCM Pin 33 on c1 is the TCC brake switch but to my understanding that is only needed if its an auto, can someone confirm that this isn't needed for the manual t56? if its required it seems I can just branch off the "open with clutch or brake" circuit. I may try this as it can't hurt anything.

The questions I have.
Is there any leads to the PCM that tell it the cruise switch is on? I've seen references to this but there isn't one in any of the pin outs or schematics I've seen. I see in hptuners there is a flag for cruise on/off so I'm assuming some pcm's do but probably those are drive by wire.

Aviator857

ok c1 33 was never wired in the PCM so that is not it. The CPP switch may have had a short in it testing that now.

Aviator857

Turned out the wire I used to ground the clutch position sensor that feeds back to the PCM had a break in it. I had grabbed it as a temporary ground until I finalized it... err its always when you put something in temporary that it bites you.

With the cpp grounded right, the PCM now sends the proper signal to the crusie module and it will set. The inhibit control in hptuners also now works.