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Discussion Starter · #1 ·
Hi- new member so please excuse my faltering steps.
I could use a little help on my Sierra. For the past couple of years the cruise control has an intermittent problem working as designed. Sometimes it worked great, sometimes it would not work at all. Working, dash light on, not working, no dash lights. I found the multifunction turn signal switch had a cracked arm, so replaced it. Still no CC. I inspected the brake light switch, found the first set of points had arced so badly the metal was always in contact. OK, bad brake switch. Replaced and r/tested again, still no cruise control, no dash light either. Tested the speed sensor, speedo works fine. Of course I checked the fuses, both marked cruise and all fuses under the hood. I think there is a test procedure for the throttle control module wiring plug, however I cannot find the wiring diagram or a simplified procedure using a Volt/Ohm meter with auto ranging scale. Any Ideas? I do not want to just start buying parts, my training is to diagnosis first!
 

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the cruise control module may have wiring problems or be defective. the brake switch that is used to apply rear brake lamps also reports to the PCM the brake pedal position . the PCM then will control the cruise operation brake on cruise off. I would also check the PCM wiring / connectors.

since it does nothing and you checked all the fuses ALL THE FUSES [?] , then it may be the cruise control switch. if you use this function all the time I would replace the switch since it must be worn out by now . cracked arm would mean these switches got tweaked.

you want to trace the circuits you will need a shop OEM manual or ALLDATA subscription .
 

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Discussion Starter · #3 ·
As a habit I check all fuses while I'm at it, a CYA function. Specific fuse in cab for cruise control has power across it. I did replace the cracked multifunction turn/signal/cruise control switch, the defective brake light switch assembly and verified the speed sensor was working with a auto raging multimeter. Also R&I cleaned and checked all the PCM connections. I do not want to trace the circuitry at this time, what I need to do is verify voltage and function at the cruise control module, I need the breakdown of the plug in connector with the functions of the wiring to it. In other words, power, signal etc. So I can verify (diagnose)if indeed the cruise control module is defective. Can you provide this?
 

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Discussion Starter · #4 ·
BTW, this is on a 2001 GMC Sierra 2500HD 4x4 SLT model, 6.0L engine, Trans. code 4L80-E. I can provide the VIN if requested.
 

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cruise control module wiring should be like this A is the on command from sw. 12v, B is the set command 12v ,C is the R/A 12 V, D is the cancel 12v cruise should be on, o V then it is cruise off, E is the ground, F is the feed from the cruise fuse 12 V, G is from stop lamp brake switch 12 V the cruise is OFF, K is the VSS which goes to the radio to increase volume as speed increases this is taken from this to the cruise module, J is the indicator lamp 12V the cruise ON..
less than 24 MPH cruise off.
I and H are not used.
This is from the 2000 shop manual should be the same.

this is the other component that does fail along with the switch . the switch takes a good beating. this cruise control module , under the hood is easy to get damaged from exterior slop.

this is with the non electronic throttle control ...
 

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cruise control module wiring should be like this A is the on command from sw. 12v, B is the set command 12v ,C is the R/A 12 V, D is the cancel 12v cruise should be on, o V then it is cruise off, E is the ground, F is the feed from the cruise fuse 12 V, G is from stop lamp brake switch 12 V the cruise is OFF, K is the VSS which goes to the radio to increase volume as speed increases this is taken from this to the cruise module, J is the indicator lamp 12V the cruise ON..
less than 24 MPH cruise off.
I and H are not used.
This is from the 2000 shop manual should be the same.

this is the other component that does fail along with the switch . the switch takes a good beating. this cruise control module , under the hood is easy to get damaged from exterior slop.

this is with the non electronic throttle control ...

Hello new member today, I was wondering if this post has photos attached and maybe I am doing something wrong?
 

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same truck as above but I have the 8.1 with the Allison
2001 GMC 2500HD 4x4 CC, 8.1

same issue

I purchased this truck in July and the cruise control is not working... so far I have tested all the fuses under the hood and on the side panel all OK, all brake lights are working fine, replaced the multi-function switch/cruise control switch on the column, replaced the brake switch....and here is where it gets funky I noticed they had cut the purple wire on the brake switch and ran a jumper wire from the purple wire through the firewall to the PCM? Does that wire control the cruise maybe? and why would that be done?

Thanks
John
 

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Check your ground at your third brake and check to make sure your third brake light works

I just spend two week trouble shooting mine to find out it was the third brake light
 

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Blitz491

Exact issues I'm having, as well as the magical wires that seems to be jumpered out at the brake switch. I have just replaced the multifunction switch. All fuses are good, and hopeful the new switch is working properly. One thing I have issues with is an intermittent abs/ brake light - dash lights - coming on due to speed sensor fault. Now, I'm guessing that this could be my reason that it is not working. But, I'm hoping to find out more on the wires that are jumpered out at the brake switch. I'm also open to any and all suggestions. Going to be looking closer to brake switch, and third brake like function.

Truck is a 2000 Silverado 2500/ 6.0 4x4 automatic.
 

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Blitz491

Exact issues I'm having, as well as the magical wires that seems to be jumpered out at the brake switch. I have just replaced the multifunction switch. All fuses are good, and hopeful the new switch is working properly. One thing I have issues with is an intermittent abs/ brake light - dash lights - coming on due to speed sensor fault. Now, I'm guessing that this could be my reason that it is not working. But, I'm hoping to find out more on the wires that are jumpered out at the brake switch. I'm also open to any and all suggestions. Going to be looking closer to brake switch, and third brake like function.

Truck is a 2000 Silverado 2500/ 6.0 4x4 automatic.
Sorry do resurrect a long dead thread as a newbie. I found this thread via google search, but I'm curious if you got your problem fixed. I'm having the exact same issues with my 01 Silverado 2500/6.0 2wd. Intermittent ABS/Brake light plus no cruise control. I can hear the cruise module click on (the box mounted on the firewall under the hood, directly in front of the driver) when I switch the controller on the column to the "on" position, but I can't ever get it to actually set. I'm assuming this is due to a speed sensor fault somewhere. It was taken to the dealership years ago who said there was an issue with the ABS controller/module/something like that. It's been just a ranch truck since then so no real need for cruise, but I bought it from my family and I'm using it as a daily driver so I'd sure like to get cruise back, preferably without shelling out for crazy new modules and computers.

Any clues?

Thanks
 

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Blitz491

Exact issues I'm having, as well as the magical wires that seems to be jumpered out at the brake switch. I have just replaced the multifunction switch. All fuses are good, and hopeful the new switch is working properly. One thing I have issues with is an intermittent abs/ brake light - dash lights - coming on due to speed sensor fault. Now, I'm guessing that this could be my reason that it is not working. But, I'm hoping to find out more on the wires that are jumpered out at the brake switch. I'm also open to any and all suggestions. Going to be looking closer to brake switch, and third brake like function.
Truck is a 2000 Silverado 2500/ 6.0 4x4 automatic.
ABS light on you need a scan tool to document the codes and post here then you will get some help no codes no help..
need a scantool that is capable to read GM ABS codes......................

most likely the front hubs are rusted up .. speed sensors are calibrated to properly set in place to provide the proper volts and gap from hub encoder.. I am not saying this is the problem but it can be the problem .. codes first then this will indicate whats up..
 

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ABS light on you need a scan tool to document the codes and post here then you will get some help no codes no help..
need a scantool that is capable to read GM ABS codes......................

most likely the front hubs are rusted up .. speed sensors are calibrated to properly set in place to provide the proper volts and gap from hub encoder.. I am not saying this is the problem but it can be the problem .. codes first then this will indicate whats up..
I'll see if I can get ahold of a tool to scan while the lights are on. The lights are intermittent so I'll have to drive around until they come on and then plug in the tool before they go back off, I reckon. I do want to confirm that notion from the (very small town) dealership mechanic that the ABS controller would affect the cruise control. Does that hold water?

The truck has sat a lot in the last 18 years. Like I said, it was a farm truck and was used sporadically for short hauls and runs to the feed store. So rusted hubs would make some sense. I'll see about popping the wheels off and looking at the hubs later today. I might experiment with the radio volume increase feature to see if the module is sending that speed signal to the radio at all. Little bit of troubleshooting.

Thanks
 

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Not sure if they are the same, but my 2009 silverado had a problem with cruise control not coming on and if I tapped the brake first it would set. Turned out to be the brake switch on the brake pedal. Relatively cheap. When you brake it tells cruise control to stop, but old switch gets stuck in this mode causing you not to set cruise control.
 

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A lot of cruise control operational problems are caused by the brake light switch out of adjustment or failure.

The other is the cruise control engagement switch where people "mash the chit out of" the contact switches like it's a video game button.

On the most part, people don't screw with their cruise control parts too often, hence the rarity of cruise control problems.
 

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Hi I'm new to this form I recently lost my cruise control and I checked voltage on all pins and the one that doesn't have any voltage is the pin B which is the set/cost command all the others function or have voltage I also noticed that when the cruise control module is connected and have my turn signals on, the third brake like and other brake lights flicker alittle with the turn signal what I'm referring to when I say flicker alittle I mean the third break light and other brake light illuminat alittle and when I disconnect the control module it doesnt do that I'm not sure where those lights get the ground from idk if that could also be the reason why I dont get voltage on pin B when we try to set the speed or press the set button.
 

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Hi I'm new to this form I recently lost my cruise control and I checked voltage on all pins and the one that doesn't have any voltage is the pin B which is the set/cost command all the others function or have voltage I also noticed that when the cruise control module is connected and have my turn signals on, the third brake like and other brake lights flicker alittle with the turn signal what I'm referring to when I say flicker alittle I mean the third break light and other brake light illuminat alittle and when I disconnect the control module it doesnt do that I'm not sure where those lights get the ground from idk if that could also be the reason why I dont get voltage on pin B when we try to set the speed or press the set button.
I also dont think it's my combination switch which I recently replaced do to the fact that I eouldnt be able to turn my high beams on.
 
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