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DBW Cruise Issue
I installed a cruise control setup today on my 70 gmc and it will not activate.
I used the parts and method in this post by ACKATTACK. http://67-72chevytrucks.com/vboard/s...d.php?t=398006 I checked all the relays and they are working as shown in the above thread. I double checked my wiring from the TAC module as well. It will not turn on (I can hear the relays though) or respond in any way. Any ideas for what I need to look for? |
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Also, I am using a GPS speedo, if this has anything to do with the issue.
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Have you verified that you are getting a constant 12v at the 'on/' wire pin 14 on the TAC? Orher than that, make sure you have the brake switch adjusted properly.Also, make sure pin 6 is hooked to the brake light switch that is hot when the brakes are applied. You dont have LED tail lights do you?
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Yes I do have Led Tail lights.
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These guys are probably right about the LED tail lights. I'll add that the GM PCMs are not quite as picky about low resistance and don't have to have the resistor packs.
Stop at your local Radio Shack and pick up a pack of 1K ohm 1/2 watt resistors. There will be 5 of them in the pack, but you just need 1. I find it easiest to place it at the tail light but you can place it near the brake switch if you prefer. It just needs to be connected from the ground wire to the brake signal wire. The resistor is not polarized, so which lead is which doesn't matter. The 1K ohm resistor won't even pull 1/4 watt, so it'll be cool to the touch unlike a spare bulb or resistor pack. |
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I will give it a shot hopefully this afternoon.
Thanks for the info guys. |
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I am not going to be able to swap out the 1157 due to my led tail lights being wired in to my harness. (Repop taillight buckets)
I have some resistors left over from my swap. I used them for my tach to cut out some electrical noise. http://lt1swap.com/lsx_tach.htm Would they work? Also does this need to be one side or both tail lights? |
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Got the resistor in today. Put it on and am still not getting any response from my cruise.
I can hear my relays working when I move the switch. So I do not think my issue is there. Does the cruise need to be turned on in the tune? |
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I think for all intensive purposes, the engine and computer don't care if the truck is in cruise, at least with GenIII engines. Its possible GENIV is different because of DOD's use in cruise, but other than that...its not like there's "cruise" setting or anything.
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Double check the adjustment on that brake switch, I was stumped with mine and slowly backed the switch away from where it bottoms out and started working. Worth a try.
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Stop guessing without real data. You guys are funny. You throw suggestions out like popcorn. What's next, replace the gas cap?
OP, go find someone who has HP tuners, datalog what the inputs and outputs are doing and troubleshoot it logically with real data. Otherwise you are just guessing. In hpt, the satus bits will tell you if the switches are commanding cruise, brake pedal status to the PCM and it will also tell you if the output is enabled among other things. |
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If you really want this thing to work, pm me your phone number and I can talk you through troubleshooting it over the phone with a simple voltmeter.
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I am going to drop by and have my tuner take a look at it with HP tuners.
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I've always used a relay with LEDs and cruise.
LED Tail Lights Note The use of LED tail lights requires a five-function automotive relay to bypass the brake system. LED tail lights do not let the violet wire (cold side of the brake switch) see ground through the brake lights, themselves. Wiring in a relay is as follows: http://www.rostra.com/manuals/250-4382_Form5260.pdf |
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LED flasher wont help.
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If not, what size of resistor should I wire inline with the LEDs then? |
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http://www.the12volt.com/installbay/...asp?tid=130800 |
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You don't need to wire up the relay to act as a relay. You can use just the coil side of it wired to the cold side of the brake light switch and ground, the cruise will see it's ground through the coil and allow it to work. This is how I do mine and they work perfectly. I use micro relays, solder the wires to the terminals and tape it up in the harness. You can see a pic in my build thread post #122
http://ls1tech.com/forums/conversion...-c-10-a-7.html It's doing the same thing as a resistor, but they don't get as hot as a resistor can get. |
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My truck has a 2005 LS DBW, 6spd mtm from a CTSV. I dont have access to HP tuners, but feel this might be next. Any input would be appreciated. |
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Thanks for responding, I'm using the engine and trans from The caddy. The harness is from Howell. They put together the pcm, tach module, pedal, maf, throttle body from what would likely come from a 5.3 in a truck(long story) They programmed the LS6 fuel maps into the truck pcm. I'm running an Autometer electric speedo.
The cruise switch is from Rostra and wired through relays with results at the tach module harness connection as follows: pin 14 brown =12v power with key on. pin 4 dark blue=power when set button pushed pin 5 gray=power when resume button slid over pin 6 lite blue=power when brakes are applied Standard tail lights, no led's Help!!! |
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Update!!!
I don't get my hands on code reader's too often, but i just did a live data scan and found out my VSS is reading at half actual vehicle speed. I thought OK it thinks I'm not going fast enough to set the cruise. I promply went looking for somewhere to go at least 80-100 he he. Well it didnt set at 90 so im back to the drawing board. I do believe this will need reprogrammed, but not sure if its related to the problem. My Yukon sets at 25mph. At least i know the vss signal is reaching the pcm. |
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Following, maybe I will learn something!
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Thanks again for your time and interest. The long story for the harness goes like this. I had Howell build the harness and program the pcm. I installed it, but all it would do is start and idle. they had me send them the entire system to bench test. They were stumpted. They offered to swap my CTSV components for the truck parts. I took the deal. They rewired the harness(blue/green connectors), reprogrammed a pcm, new tach module, accell pedal and throttle body. The MAF is original CTSV.
It all looks like parts from my 2004 silverado 5.3L which is the configuration they built it around from what i was told. In fact I have swapped the tach module from the 5.3 for a test, but it didnt fix the cruise. The components should all match as far as I can tell, but with all the changes its anyone's guess. I've made one call to get help from Howell, but so far all i've gotten is a schematic for the switch. I know this is as real cluster and harder than it should be to trouble shoot. They built it to be a truck setup with the 2002 vette LS6 tune. |
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There are two brake light switch wires that need to be hooked up, do you have them both hooked up? One hot when brakes applied and one hot with brakes not applied.
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I only knew of the one brake light wire. Its lite blue and comes from pin 6 at the tach module and is connected to the cold side of the switch. All the harness wires were tagged and accounted for. I have verified ground ay the switch back through the brake light bulbs and also by wiring in a tempoary 3rd brake light.
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There should be a purple wire on pin 33 of the blue connector that needs power with the brakes not applied, do you have that hooked up?
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Am i to understand that the purple wire leads from the pcm and terminates at the brake switch cold side? Would this be instead of the pin 6 from the tach module? I won't be able to check this till next week, but i will definetly look for that wire!!! I appreciate your help and can only hope you continue to enjoy a good challenge.
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I reviewed your post and I will check for power at pin33 when the brakes are not applied.
Thanks |
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You'll need a 4 prong brake light switch, the kind used for cruise control in the 70's and 80's. They have 2 sets of contacts, one normally open and one normally closed. The TAC ties into the cold side of the brake light wiring and the PCM side will be the other set that needs ignition power and will send power to the PCM when the brakes are not applied.
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Make sure when you adjust the brake light switch that the tcc wire has power in and out without the brakes applied.
I had a problem.with the cruise not working. Turned out I had to push the pin in further. Into the barrel of the switch to make contact. Doing that I now have to push the brake pedal down further for the brake lights to come on |
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