Thanks ls1nova71 for the help on cruise

[ls1nova71]

Originally Posted by truckdude239

i have yet to hook mine up on my 2004 4.8 dbw ive read alot about having to use relays i just wanna find something i can hook right to the wires of the tac module

The relays are for aftermarket column mounted cruise switches. The only ones that work without them are factory GM switches and the dash mounted ones from DD and Rostra.

[truckdude239]

So if i got tbe one like on the old blazer where its on the turn signal stock it should wire rigbt in

[NC_John]

Originally Posted by ls1nova71

The inputs all come from the switch, so what are you seeing? Just the brake inputs on the TechII?

Not sure what you mean so I videoed how I go through everything with this scanner. I can see all the input statuses the PCM is looking for to run cruise control and, when my stuff is working correctly, watch each status change real time.

I did the brake pedal first (two inputs change status), and then did the buttons and slider on the control stalk. You can see it's not even looking for a clutch pedal switch (may have to change to the corvette tune if this keeps it from working)

https://youtu.be/ahPk84w353c

[ls1nova71]

Originally Posted by NC_John

The tech 2 sees all my cruise control inputs now EXCEPT for the cruise control switch. It's not even looking for it whether I have it set for a manual or auto transmission. I found the cruise control switch pin on my pcm but there is no wire for it. I have to see what Speartech is doing with that 12v signal.

At this point, if I were to road test it, I am somewhat confident it would work. Not 100%, but better than before.

Ok, I watched your video and everything appears to be functioning correctly so it should work. I think in this post I quoted, you meant to say clutch switch, not cruise switch, that is what confused me.

So, are you running a manual transmission? Did Speartech set the PCM up? The TechII isnt looking for a cruise input because the vehicle you selected didnt have a manual transmission option most likely. I would road test it, but if you are running a manual, dont hit the clutch with it engaged or it will shoot straight to the rev limiter without a switch on it.

[ls1nova71]

Originally Posted by truckdude239

So if i got tbe one like on the old blazer where its on the turn signal stock it should wire rigbt in

Not sure what the old blazer you are referring to is, but if it's a 4 wire GM switch it will work.

[Advanced Design]

Adding my thanks too. Though I bought the 72 Burb done, it has tap up, tap down cruise that works great. In the materials the p.o. provided was a printed copy of the cruise thread you created. Thanks again!

[NC_John]

Originally Posted by ls1nova71

Ok, I watched your video and everything appears to be functioning correctly so it should work. I think in this post I quoted, you meant to say clutch switch, not cruise switch, that is what confused me.

So, are you running a manual transmission? Did Speartech set the PCM up? The TechII isnt looking for a cruise input because the vehicle you selected didnt have a manual transmission option most likely. I would road test it, but if you are running a manual, dont hit the clutch with it engaged or it will shoot straight to the rev limiter without a switch on it.

Yeah, might have misspoke.

T56 and speartech did not set the pcm up. My builder and his tuner set it up through HP Tuners. We selected manual transmission but like Justin at ST said, cruise might not work on an 04 truck tune with a manual transmission as that combination may not have been offered from GM.

I haven't been able to figure out how to incorporate a clutch switch. There just isn't a good place to mount one. I was just going to duplicate the brake pedal setup but the pedal geometry and lack of room under there on the clutch side doesn't make it easy.

[truckdude239]

https://www.summitracing.com/parts/rpc-250-3020

Was what i was looking at but its a rosta and i read will only work aftermarket and not oem with out relay any idea on a gm switch that works

[ls1nova71]

Originally Posted by NC_John

Yeah, might have misspoke.

T56 and speartech did not set the pcm up. My builder and his tuner set it up through HP Tuners. We selected manual transmission but like Justin at ST said, cruise might not work on an 04 truck tune with a manual transmission as that combination may not have been offered from GM.

I haven't been able to figure out how to incorporate a clutch switch. There just isn't a good place to mount one. I was just going to duplicate the brake pedal setup but the pedal geometry and lack of room under there on the clutch side doesn't make it easy.

If you are running a 2004 truck tune then it should work the way you have it wired up. As far as I know there isnt anything specific to the automatic transmission that would stop it from working. If you had the Vette tune then it would, but since you dont have that it should work.

As far as the clutch switch goes, I dont have a clutch pedal set up to look at but looked at my auto one and it looks like it would be doable with a brake switch, but you would have to weld (or bolt) a tab to the pedal bracket. If that isnt possible, adding a switch to the bracket that goes under the steering column where the pedal bump stop is would be an option. When wiring it, I dont know if adding the wire to the PCM will work if the tune isnt set up for it, so the easy way around it would be to have the 2 switches wired in series so that anytime one is pushed the PCM will think the brake is applied and would cut the cruise off.

[ls1nova71]

Originally Posted by truckdude239

https://www.summitracing.com/parts/rpc-250-3020

Was what i was looking at but its a rosta and i read will only work aftermarket and not oem with out relay any idea on a gm switch that works

The only factory switch that will bolt to an old column, the single screw type, is one from an 83 Chevy truck. 81-83 or maybe 84 will work but some are 3 wire switches and need the switch chabged.

[NC_John]

Originally Posted by ls1nova71

If you are running a 2004 truck tune then it should work the way you have it wired up. As far as I know there isnt anything specific to the automatic transmission that would stop it from working. If you had the Vette tune then it would, but since you dont have that it should work.

As far as the clutch switch goes, I dont have a clutch pedal set up to look at but looked at my auto one and it looks like it would be doable with a brake switch, but you would have to weld (or bolt) a tab to the pedal bracket. If that isnt possible, adding a switch to the bracket that goes under the steering column where the pedal bump stop is would be an option. When wiring it, I dont know if adding the wire to the PCM will work if the tune isnt set up for it, so the easy way around it would be to have the 2 switches wired in series so that anytime one is pushed the PCM will think the brake is applied and would cut the cruise off.

Yeah, if its not looking for a clutch switch status, it shouldnt be in the logic path.

With the interior fully assembled, any kind of welding in there is going to be a bigger hassle than its worth (if I could even get it up there) I wasn't able to find an easy bolt on location (that was my first thought). It's miserable trying to do anything under there, as cramped as it is. I'm way to big to get folded up the way the space requires. I've actually gotten stuck under there. Might be able to put a pressure switch in the clutch line if the fittings would work.

Good idea putting the switches in series.

[truckdude239]

Originally Posted by ls1nova71

The only factory switch that will bolt to an old column, the single screw type, is one from an 83 Chevy truck. 81-83 or maybe 84 will work but some are 3 wire switches and need the switch chabged.

Okay will see what i can find

[Big Moose]

Here's another Cruise Control question:


6.0L / 4L80e out of a 2005 2500HD swapped into a 1985 C3500
DBW Throttle using a harness from Painless Performance

Cruise was working for the better part of 2 years and then it quit.
Checked the brake switch and confirmed it's working.
Checked the Cruise On/Set switch on the signal lever and confirmed it's working. I checked these at the TAC plug to make sure the harness wasn't at fault So I decide it must be the TAC, tried 2 different TAC modules and still nothing.
I was wondering could the pedal or the throttle body be at fault and how would I be able to test them

[ls1nova71]

Generally when the cruise stops working on those trucks, its due to the wires breaking inside the column that go to the switch, but if you've checked them, that must not be the case. Have you changed anything that could have caused it? LED brake lights for example. So you checked for power at the TAC for the set/coast and on/off and they have power? Also, its possible that the brake switch is out of adjustment since they went to the push in type of brake switch rather than the actual bolted in one, so you might try pushing it back up a bit and see if that helps.

[Big Moose]

Ls1nova, thanks for replying

The Painless Performance kit had a new brake switch supplied with it, which I installed and it seems to work.
No, don't have LED taillights.
I had a problem for a while with the cruise on/off set/resume switches failing, aftermarket junk, went through 3 of them, til I found an AC Delco and so far it's still working,
Would it be possible to somehow check if the TAC is getting a vss signal?

[ls1nova71]

There really isn't any way to test a TAC module other than trying a known good one, but if your throttle is working, then the TAC is good. It doesn't get a VSS signal, that is done in the PCM, so if you weren't getting that, your transmission wouldn't shift correctly. I would still try adjusting the brake switch though. What happens is the two sets of contacts don't open and close exactly at the same time inside of it, so when you let off the brake the first set of contacts open, and the brake lights go off, not always will the second set of contacts close at the same time, so you will be sending the wrong signal to the PCM, and there is a lot of fail safe built into the cruise control.

[Big Moose]

I'll try a new brake switch next, but I've tested it at the switch and at the TAC plug and it seems to work properly. but maybe it is faulty and just happened to work when I was testing it.

[Big Moose]

Turns out it was the brake switch, I tested it again and found out it didn't always have continuity, even though it was a new one, aftermarket junk doesn't seem to last.
Thanks, for the help Ls1nova

[NC_John]

Originally Posted by NC_John

Yeah, if its not looking for a clutch switch status, it shouldnt be in the logic path.

With the interior fully assembled, any kind of welding in there is going to be a bigger hassle than its worth (if I could even get it up there) I wasn't able to find an easy bolt on location (that was my first thought). It's miserable trying to do anything under there, as cramped as it is. I'm way to big to get folded up the way the space requires. I've actually gotten stuck under there. Might be able to put a pressure switch in the clutch line if the fittings would work.

Good idea putting the switches in series.

Circling back on this for some closure- I ended up getting the 2004 corvette Z06 base tune flashed on my PCM instead of the original truck program. As speartech thought, there was no cruise control option for a six-speed transmission in a truck.

I did also end up putting in a clutch switch- I found a rostra "universal" kit that I was able to make work. I've got a video clip of it on my instagram if anyone wants to see what I came up with.

So I have working cruise control in my '70 and it is cool as heck.

Thanks.