CHMSL signal to cruise control necessary?

[914turboford]

Is it necessary to have the centrally high mounted stoplight signal going to the cruise for it to function on a 3.4 Camaro? If so, what is this signal? 12v positive? Some sort of resistance to ground?

Brian

[98Camaro3.8]

On the 3.8s: "Terminal G must see a ground path through the CHMSL bulb in order for the cruise to operate properly." It's from the collision light in the rear of the car. I assume this has something to do with how it trips off the cruise when you press the brake.

[914turboford]

98Camaro3.8,

Thank you. It sounds like you have a factory manual or something. I am trying to get cruise working on my Volvo 245 that has a '97 3.8 and a 700R4. I am using a cruise from a 3.4 camaro. The car it came from did not have the cruise inhibit and cruise engaged wires to the PCM. At first I had a cruise from a 90 pickup without the CHMSL wire either. I also tried one from a 92 Suburban. I have not gotten any of them to work. Do you think the PCM speed signal should be compatible? I am pretty sure my speed signal is working. I have a custom reluctor I put on the rear axle and a stock VSS. I have measured the frequency to be pretty close to the 4000 pulses per mile that I am supposed to have.

I tried running 12V positive into terminal G on the 3.4 cruise so I hope I did not ruin it. I'll try groundind it. Do you think I need a resistor to account for the bulb?

Brian

[914turboford]

I just went out and looked and realized I am mixed up. I did not run 12v+ to G. I had run 12v+ to the other brake input wire, brown I think. So I went ahead and grounded G. I'll hope for the best when I drive it to work tomorrow. Do you know if on the other brake input wire (not G), if 12v+ shuts off the cruise or is it the absence of 12v+ that shuts it off? Thank you again.

Brian

[98Camaro3.8]

I don't have any information on the 3.4 cruise control system. I don't know how much of a similarity there is, so take my info with a grain of salt.


Pin D on the 3.8's cruise control module is the other brake input. That's the switch that is triggered when you press the brake or clutch. However the switch is open when the brake or clutch is pressed. So I think you'll need power into that or it'll think the brake is pressed and disengage.

Pins H and J are both inputs from the PCM that determine if the cruise control is engaged or not...in addition to the main cruise control switch on the turn signal lever that goes to pin A.

[914turboford]

Cool. Thanks. I'll try that this morning before I drive to work.
A couple more questions: In your experience have you found these cruise control units to fail frequently or are they fairly reliable? Based on what I have seen the 3.4 unit is the same as the 3.8 unit except the cruise status and cruise inhibit pins don't have wires going to them. Incidentally, on a 3.8 what type of signal does the pcm send to "inhibit" the cruise? Do you know if it will allow cruise based on certain conditions from the transmission?

Thanks again

Brian

[914turboford]

It did not work. I'm going to go check my signals to the cruise with my DVM before I drive home.

Brian

[914turboford]

I had the 12v+ brake input switched with the on switch wire. On my drive home I had cruise control! At least partially. The cruise would work for a while and then shut off. I could not seem to see a clear pattern to when it would shut off but I think it was after the cruise had given the car a little extra speed and then needed to coast for a bit. I need to improve some of the connections and I plan to rework the cruise cable to make it more like stock. Thanks for the help 98camaro3.8.

Brian