Thanks ls1nova71 for the help on cruise

[Custom 68]

I wanted to give some kudos to Eric for the wonderful insight on adding cruise to my swap. http://67-72chevytrucks.com/vboard/s...d.php?t=511477
This thread says it all. It is an easy swap with this set of instructions. Also thanks to all the others that added to this along. I would highly recommend this. It can be done on the cheap with pick n pull parts.
Again thanks and this is a great site with everyone willing to offer their findings.
Dave

[oldman3]

Just wanted to add that Eric is a top-notch guy, willing to help anyone with LS info. I met him in 2017 at Mid-America nats...Jim

[ls1nova71]

Aw geez guys, you're going to make me blush! LOL! I enjoy helping others with what I enjoy doing, and hope its good for at least a little good karma!

[Clyde65]

He has been that way for a long time! He helped me with my cruise control ( among other LS stuff) about 7/8 years go! Good man and very helpful!

[Daaaanz67]

Got my cruise lever from him years ago and still working. Top notch lever. Thanks again Eric.

[NC_John]

Here's a CC question. Mines not working - DBW, blue/green PCM, speartech harness, rostra cruise control stalk with relays installed as illustrated in other threads to give the newer PCM the signal it wants.

With the tech 2 I am borrowing for the weekend, I have been able to check all my control switch functions and signals to the PCM.

Cruise Control Active - No. (I assume because truck has not hit min speed required). I need to road test for this input later.

Cruise On/Off Switch - yes, input changes as I work switch on stalk

Cruise Set/Coast Switch - yes, input changes as I work switch on stalk

Cruise Resume/Accel Switch - yes, input changes as I work switch on stalk

Stoplamp Pedal Switch - (assume this to be brake pedal). yes, input changes as I depress/release brake pedal

Here is the one I don't understand-

Cruise Release Brake Pedal Switch. This does not change... but as I type this now I wonder if it won't work until the truck is at speed, cruise is enabled and functioning and THEN the brake pedal is depressed to turn off the cruise.

Anybody know for sure? I'm also not sure where it is looking for the pair of wires Speartech provided for a clutch switch. Changing that input didn't have an effect on anything the tech 2 showed.

It looks like I am real close to having my cruise control work but there is still a missing piece.

[ls1nova71]

Do you have both brake switch inputs hooked up? Should be one from the PCM that needs power with the brakes not applied and one from the TAC module that. Reds power with the brakes applied. Also, do you have LED taillights by chance?

[NC_John]

Originally Posted by ls1nova71

Do you have both brake switch inputs hooked up? Should be one from the PCM that needs power with the brakes not applied and one from the TAC module that. Reds power with the brakes applied. Also, do you have LED taillights by chance?

I've been thinking about this and crawling under the dash to look at stuff all day. I have the light blue to the brake light switch but I wonder if I have it tied to the wire on the wrong side of the switch which is why it shows no status change when I hit the pedal. I'll have to either see what I can see in the factory wiring diagram (or just switch to the other wire).

No LED tailights. Probably that light blue wire....

thanks... I might be on the right track to fix this now. I tell you what- this Tech 2 has been a HUGE help in troubleshooting. I might have to buy one of the knockoffs.

[NC_John]

I switched the blue wire from the white brake switch wire to the orange (couldn't figure out which side I needed from the service manual schematics). No change in input status but I've also lost the input change on the other brake switch that WAS working. I think I am going to stop until I get a new pcm in there. I am just chasing my tail right now with too many issues going on at once.

[ls1nova71]

All you did by switching the blue wire to the other side of the brake switch is make it think the brakes are always applied. It should be hooked to the cold side of the brake light switch/wires. So put that back on the white one. What about the purple wire that goes to pin 33 on the PCM connector? Is that one hooked up? What brake switch are you using? Its pretty uncommon for a PCM to just go bad .

[NC_John]

Originally Posted by ls1nova71

All you did by switching the blue wire to the other side of the brake switch is make it think the brakes are always applied. It should be hooked to the cold side of the brake light switch/wires. So put that back on the white one. What about the purple wire that goes to pin 33 on the PCM connector? Is that one hooked up? What brake switch are you using? Its pretty uncommon for a PCM to just go bad .

I'll put it back. Figured it was 50/50.

I'll have to check for a wire on 33 (looks like it should be on the blue plug) when I tear into the harness again.

Brake switch is an ACDelco D850A, two sets of contacts, one NO, one NC.

I agree its odd for a pcm to go but with everything I have going on right now, it's definitely a potential culprit.

[ls1nova71]

Is your PCM and TAC somewhere where you can easily remove the plugs to check for power? If so, what I would do is remove the blue PCM connector and physically check for power at the purple wire on pin 33. With the key on, check to make sure its getting power, you can use a test light since its just power from a switch, then have someone press the brake pedal and it should go off. Then check pin 6, light blue wire on the TAC plug and it should be the opposite, no light until the pedal is depressed. This is a really quick and easy test, provided you can get to the connectors.

I have also seen on several occasions cruise not working just because the switch is a little out of adjustment, so might try adjusting the switch, usually in, so that it takes a little more pedal travel for the brake lights to come on.

[NC_John]

Originally Posted by ls1nova71

Is your PCM and TAC somewhere where you can easily remove the plugs to check for power? If so, what I would do is remove the blue PCM connector and physically check for power at the purple wire on pin 33. With the key on, check to make sure its getting power, you can use a test light since its just power from a switch, then have someone press the brake pedal and it should go off. Then check pin 6, light blue wire on the TAC plug and it should be the opposite, no light until the pedal is depressed. This is a really quick and easy test, provided you can get to the connectors.

I have also seen on several occasions cruise not working just because the switch is a little out of adjustment, so might try adjusting the switch, usually in, so that it takes a little more pedal travel for the brake lights to come on.

Everything is in the cab so I can easily check that stuff with my multimeter. I'll probably get a chance to check those two wires this evening. The hurricane is long gone so back to work and back to normal after a few days at the house.

I'll check the switch adjustment if I don't see status changes on those two wires.

thanks. I'll let you know what I find.

[NC_John]

Originally Posted by ls1nova71

Is your PCM and TAC somewhere where you can easily remove the plugs to check for power? If so, what I would do is remove the blue PCM connector and physically check for power at the purple wire on pin 33. With the key on, check to make sure its getting power, you can use a test light since its just power from a switch, then have someone press the brake pedal and it should go off. Then check pin 6, light blue wire on the TAC plug and it should be the opposite, no light until the pedal is depressed. This is a really quick and easy test, provided you can get to the connectors.

Well, trouble in paradise. I didnt get what I was hoping to see on either pin. 0 volts across both in both conditions (brake pedal up or down). I need to start going through schematics and pinouts and maybe make a call to speartech when I know what to ask.

"Build an LS" they said........"it'll be fun" they said......

[ls1nova71]

Ok, this isn't making any sense at all. Speartech makes one of the best harness available, so I'm going to go out on a limb and say it isn't a harness issue. That said, have you checked all your fuses? If you are getting no power on either of those pins, you are missing two different power sources. The light blue wire on the TAC pin should be getting power from the brake light fuse, do you have functioning brake lights? I have never personally worked with a Speartech harness, so I'm not real familiar with them, but what do the instructions say about hooking up the cruise? Is it just the 3 wires that go to the switch?

[NC_John]

Originally Posted by ls1nova71

Ok, this isn't making any sense at all. Speartech makes one of the best harness available, so I'm going to go out on a limb and say it isn't a harness issue. That said, have you checked all your fuses? If you are getting no power on either of those pins, you are missing two different power sources. The light blue wire on the TAC pin should be getting power from the brake light fuse, do you have functioning brake lights? I have never personally worked with a Speartech harness, so I'm not real familiar with them, but what do the instructions say about hooking up the cruise? Is it just the 3 wires that go to the switch?

Here is what speartech provided in my harness for cruise control. Bold is from their instructions/technical sheet

http://www.speartech.com/v/vspfiles/...XManualETC.pdf

PINK & GRAY – Clutch pedal position switch. Used for cruise control. Ignore if not
needed. (Pink is 12 volt feed to clutch switch, gray is signal wire from switch to PCM).

I do NOT have a clutch switch and honestly haven't been able to figure out a good or easy way to mount one. I am working this one manually for testing.

PINK & PURPLE – Brake switch for cruise control release. Ignore if not needed. Used
with normally closed side of 4 terminal brake switch. Pink is 12 volt supply to switch,
purple is signal wire from switch to PCM. (Zero volts with brakes applied).

I have this wired to the set of NC contacts on that Delco switch I referred to earlier.

ETC Cruise Control hookup:
GRAY- Off/On (GM stalk switch)
GRAY/BLK- Resume/Accel (GM stalk switch)
DK BLUE- Set/Coast (GM stalk switch)

These are all wired with the relays to convert the older CC signal (dakota digital/rostra switch) to what the LS needs. I am seeing these all respond as expected when viewed through the Tech 2

LT BLUE- To normally open brake switch (same as wire to brake lights)

Tied into white wire on brake light switch

Pedal Harness: From electronic throttle pedal to throttle actuator control (TAC) box.

I had Speartech provide me with the TAC module to ensure everything was matched and there are no communication issues.

NOTE: All brake switch and clutch switch wiring is for cruise control only on a manual
transmission application. If cruise control will not be used, all brake and clutch switch
wiring, and cruise control wiring can be ignored or removed

So the two issues I am seeing are related to the pink/purple pair and the light blue, both directly tied to the brake switch. I do have working brake lights so I am definitely confused as to why I am not seeing voltage at 33. I'll have to check both recheck the correct operation of the brake light switch and check for continuity in that wiring with my ohmmeter. All fuses that I could find are good.

All sorts of funky stuff going on for sure. I am going to ask speartech where the pink/purple pair and the blue wire are run to through the PCM just to make sure it is correct and consistent with the info I/we have. I have the pinouts and wiring schematics specifically for my VIN (compliments of my tuner from PRODEMAND). Fun, fun, fun. These projects are an endless source of entertainment for sure.

[ls1nova71]

Originally Posted by NC_John

[I]So the two issues I am seeing are related to the pink/purple pair and the light blue, both directly tied to the brake switch. I do have working brake lights so I am definitely confused as to why I am not seeing voltage at 33.

If you don't have power at pin 33, then this is most likely your issue. I would check for power at the brake switch itself, on the pink wire to see if it has power. If it doesn't, then find out why and fix it, however, if it does have power, then check the other terminal on the brake switch, with the brakes not applied it should have continuity, thus, it will have power also. If it does have power with the brakes not applied, and you still have no power on pin 33, then your problem is in that wire between the switch and the PCM connector.

One other thing, how are you testing the cruise? Actually driving the vehicle? I ask because I have had people swear they're cruise isn't working only to find out they were trying to make it work on jack stands, which it most definitely wont!

Also, you say you don't have a clutch switch? Are you running a manual transmission? If so, the clutch switch is a normally closed switch, so by manually working the switch you will need to press it and release it at least once every ignition cycle for the cruise to operate, same goes for the brake switch. The PCM needs to see them operate before it will allow the cruise to work as a fail safe against a bad brake/clutch switch.

[NC_John]

Originally Posted by ls1nova71

If you don't have power at pin 33, then this is most likely your issue. I would check for power at the brake switch itself, on the pink wire to see if it has power. If it doesn't, then find out why and fix it, however, if it does have power, then check the other terminal on the brake switch, with the brakes not applied it should have continuity, thus, it will have power also. If it does have power with the brakes not applied, and you still have no power on pin 33, then your problem is in that wire between the switch and the PCM connector.

One other thing, how are you testing the cruise? Actually driving the vehicle? I ask because I have had people swear they're cruise isn't working only to find out they were trying to make it work on jack stands, which it most definitely wont!

I just emailed Speartech to confirm where the brake and clutch switch wiring was terminating on the PCM/TAC side. Its likely where you identified (and I confirmed on my PCM drawing), pin 33 and the TAC, but I suppose I should make sure they are following the same configuration (not sure if they changed at all year to year).

I'll check the switch, voltage supplies, continuity etc.

I am testing the cruise control through the GM Tech 2. There is a screen under engine outputs (IIRC) that has the cruise control inputs all listed and shows their current status. I could confirm operation of all the stalk controls by watching their status change on the Tech 2 but can't get the brake side statuses to change. If I can get all the statuses to change when commanded, the CC should work on a road test. I know my speed signal is good since we changed that through HP Tuners (and my speedo is reading correctly).

I am borrowing the Tech 2 from my wife's work (chevy dealership) and will have it back again to use this weekend. Its a great tool. I want one! Its proving valuable in my no-start issue as well.

thanks for your help with this. I owe you a beer.

[NC_John]

Got some really good info from Justin at Speartech. He confirmed wiring and termination points across the switches, PCM and TAC. He also mentioned I may want to use the 2004 corvette base tune instead of the 2004 truck. I'm not near that point in troubleshooting yet but it might come up later. Here is what he had to say about it -

The 2004 Vette Blue/Green PCM is known to support cruise control. When we test with some of the truck manual files the clutch switch doesn't always change in the tech 2 but with a Vette file it does. Not sure if trucks don't utilize a clutch switch or not, which I would imagine they would to cut the cruise but you never know with GM. Heck, the manual trucks may not have cruise from the factory so you may not be doing anything wrong. So the Vette file would certainly give you a better foundation file for working cruise. I'm just speculating and haven't confirmed via GM schematics but if we were the ones that would have done your base file for this setup it would have been Vette based.

[NC_John]

Got some good figuring out done tonight. Found a few problems that got resolved.

One of my multimeter test cables had a continuity problem so I wasnt getting a good ground for readings. Got that fixed.....

I found my 12v at 33. I had to remove the brake switch and really work it to get that second contact closed far enough. I'll have to reinstall it and see if I can adjust it enough so that both functions work as I need (n.o. and n.c. sides).

I also found my voltage at the tac. I was reading the wrong plug - the one that went to the pedal. I've pulled the harnesses from under the carpet and was able to trace the bundle to spot my mistake.

I have to figure out if the clutch switch input is going anywhere. By the tech 2, the pcm is not even looking for that signal. I've got it back for the weekend so I can do some testing.

I need to go through all the rest of the harness tomorrow ro see if I can figure out what is going on with my no-start nomsense.

At least it feels like I made some progress.

[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.

[BR3W CITY]

This is interesting, because I've been looking at doing the absolute most minimal cruise setup possible. Don't need a stalk, just want a single "cruise" switch with the brake safety.

[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

[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.

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

[ls1nova71]

Originally Posted by BR3W CITY

This is interesting, because I've been looking at doing the absolute most minimal cruise setup possible. Don't need a stalk, just want a single "cruise" switch with the brake safety.

Super easy. Just make sure the brake switch is wired up and hook a momentary switch on the SET wire on the TAC to 12v.