goatcrazy

I've got an '04 LQ9 6.0 (DBW) + 4l60E setup in my '69 LeMans, and I'm trying to get cruise control working. I've read all of the previous posts on the subject, and I've wired everything up according to the GM factory service manual and it just won't work. I've rang out the wires from the cruise switch to the pins on the TAC and ECM and everything is right. I've also connected to the PCM and there are no codes.

Here is my connection setup:
Cruise on (N.O.) pin 14 TAC
Cruise Set/Coast (N.O.) pin 4 TAC
Cruise R/A (N.O.) pin 5 TAC
Stop Lamp supply voltage (N.O.) Pin 6 TAC
Brake Switch Signal (N.C.) C1-Pin 33 ECM

The brake/stop lamp signals act together (both change state) when the brake pedal is depressed.

I've read multiple views on the matter ranging from:
1) Hooked everything up no problems
2) Needed to add a light bulb in the CHMSL feed to the TAC or it doesn't work
3) Can't get cruise control to work on DBW engines because the PCM needs to talk to the ABS module to ensure it's not active

Has anyone been successful with this powertrain combination?

What could I be missing? Any help would surely be appreciated!!

G-Body

iTrader: (4)

Works great on my brothers car. I did have some teething problems which you probably read about. Once I wired pin # 6 to the actual brake light circuit (since it looks for the actual bulbs via resistance to ground when your foots off the brake) it has worked very well. Did you just give pin 6 voltage when the brake pedal is depressed? or did you actually wire it to the actual brake light bulbs?

goatcrazy

I actually wired it directly to +12volts. Looking at the schematic, it appeared that the feed for that circuit came directly from the I/P fuse block and did not go "through" the stop light. So I did not understand how the TAC could "sense" resistance if it doesn't go through a device...

But on the other hand at this point I'll try anything. I'll go to autozone and pick up a bulb socket and bulb and give it a shot.

I also read the threads a bit more carefully and it sounds like the TAC module sends +12V out on pin 6 as a start-up check, is that correct?

I'll let you know if it works..

goatcrazy

SUCCESS!!!!

Thanks G-body, I guess I miised the fact that the TAC sends a +12v pulse out for a check, now it makes sense!!

SamHatco

iTrader: (1)

Congratulations! Sooo....want share with us what you did? I had cruise problems on mine and it was the disengage circuit not getting 12v+.

Sam

goatcrazy

I actually had +12v going to the disengage circuit (pin 6 on the TAC) but apparently when you first power the car up, it sends a test pulse out on pin 6 and looks for ~6 ohms of resistance to ground. I wired mine (through a relay operated from the brake light switch) directly to +12v, and it failed the start-up test. To correct this, I went to autozone and bouught a socket and 1157 tail light bulb, and wired the positive to the side of the relay going to pin 6, and the other side to ground. It worked right off the bat!

So for now I have a light under my dash that goes on every time I hit the brake pedal, this winter I'll correct this and wire that side into the tail light circuit for the car.