Im glad you put this series together thank you! I confirmed its on the truck side just replaced the 7 pin coupler. Problem persists I noticed at 3:59 you mentioned a secondary lock. Mine seems to be missing had the bumper replaced. Dealer said they can't find a part number for the secondary lock. Would that come with the wiring harness? Im assuming missing the secondary lock would contribute to the issue?
I know it's a old video, mine is a 2015. Maybe you can tell me where the chsml wire is ? Trying to tap into it for the 3rd brake light on my topper. Thanks
Try Alldatadiy.com for wiring diagrams and connector locations. It's not free but it's pretty reasonable. Alternatively you could tap into the circuit at the brake switch. I'll have a look at the wire colour and get back to you...edit. the brake switch is an input to the bcm which controls the chmsl relay under the hood. The circuit runs through the cab through the instrument panel junction block under left side of dash. Connector x2 and x3 a violet/grey wire. Try to find it there is my recommendation.
have a Chevy 3500 wt my service trailer wiring light comes on my dash spelled out with exclamation point, my left blinker and brake light don’t work only left side running lights are brighter on left side also. Tech said he’s getting power on all 7 prongs on my trailer hopkin connecter a snap on code reader saying it’s the brake control module and pressure valve and my code reader says c0800-5A control module not plausible please help
@@PhillipBailey it is a 2019 , I took apart the Hopkins plug black melted tape or grease was on it wonder if it’s bad one prong kept bending that same prong controlled the left signal
I have a '21 3500 and 02 2500 chevy. I tow daily with the '21 and have gotten the check trailer wiring message on 3 occasions now. The trailer brake control module and 30 amp fuse were changed the 1st time...work fine for 1 month. Took it in and I don't even know what they did to fix, but it wasn't a module replacement. They said it's on the trailer end and printed the bulletin for me to follow. I ordered a new 7 pin connector and just wired it up and I still have the same message on the dash. The fuse is OK. My trailer brakes work just fine with my '02, but at 200k+ miles I don't like hauling with it. What the hell is the issue with this?
@@shaymoose17 if its not communicating with their scan tool the it should be under warranty I would think unless you have a ton of mileage on it. I would agree that if tge brakes work on the trailer when towing behind the 02 that the trailer is not the problem. Is the 02 factory trailer brakes or aftermarket controller? If it's aftermarket brake controller then it is more forgiving of issues with the trailer. If the truck is under warranty I'd try a different dealership if possible. You might also try towing a different trailer with the 21 see if you get the same message. There should be a code if that message is coming up.
@@PhillipBailey I haven't towed with any other trailers since the issue had come up. There's 15k miles on the '21 and started using issues around 13k miles. The 02 is an aftermarket controller. I was told the trailer plug is the culprit and the for may be too loose. So I ordered the plug they recommended, hooked up with no success.
@@shaymoose17 ah the aftermarket controller is not as sofistcated as the 21 system and as such may not be as sensitive to an actual problem in the trailer. Given the low mileage on the 21 I would bet the issue is in fact in the trailer. Could be an intermittent break in the trailer brake circuit wire or trailer ground. Does the message on the 21 come up as soon as you plug into your trailer or when you start driving it. It would be best to either tow a different trailer with the 21 or tow your trailer with a newer preferably 21 truck to see what happens.
I only have an issue when I am actually hooked up to my camper. It will jump back and forth between "Check Trailer Wiring" and "Trailer Connected". Funny thing is all the lights work and the trailer brake functions. My truck is a 2016 2500HD with a 6.0 engine. Any ideas?
hi Phillip, maybe you can help me please!, i have a 16 sierra 5.3. for unknown reasons, i have power in my trailer hitch all the time now. meaning the pin that powers up the batter in a trailer. that usually turns off when you take the key out of the truck, now theres always power, i have a truck camper and its draining the truck battery, it didnt do that before
I'm pretty sure that auxiliary power feed is live all the time. Older camper vehicles used to use two batteries under the hood with an isolator. Ill have a look at the circuit and get back to you here.
Just looked at the schematic and the auxiliary feed come from a 30amp maxi fuse that is hot all the time. Something is on in the trailer or if it has a battery in the trailer might be a bad cell in it. Not sure how new the trailer is. Do you have a TV plugged into a 12 volt source in the trailer. Even if its off the inverter in it will draw power. Hope this helps
Hi Phillip. I have a 2021 GMC Sierra AT4. Without any trailer attached I get check trailer lights, disconnect etc error messages constantly. I even detached the connector to the 7 pin and still am getting all the check trailer lights and disconnect messages. Connections are clean and dry and in good shape with only 6000 miles on the truck. Any thoughts would sure be appreciated! Thank you.
Isn't it still under warranty? You need to scan the system for codes and refer to the appropriate troublemaker chart. There are many things that can generate the dash message but need the code/s to proceed.
Similar problem, I'd like to know if you can help me with mine. Trying to troubleshoot but not sure on some issues. Let me know if you would be willing to help me out. TIA
I don't believe it does. The right turn signal brake circuit is supplied from the KR63R relay in the underhood fuse center. Check for power at fuse F17 with the signal on or brake applied. It is fused separate from the other circuits. If that is good then other than the connections under the fuse center there is no other test points of connectors til you get to the trailer plug itself. Unplug the back of it and check there. Should be a Green/Violet wire to pin D. HTH
If you are measuring voltage at one of the turn signal circuits and ground with it on you should see a pulsing battery voltage in sync with the signal lights flashing. Hope this is what you're asking...
@@PhillipBailey thank you for the quick response. I’m having issues with my 2014 GMC Sierra causing the trailer lights to go crazy, any way that you could help? I’d greatly appreciate it
Looking forward into your videos with the 19.4 update. I think I’ll eventually get mine to that point hopefully mid year. Im itching really bad for a pico.
I agree that the Pico is a superior scope to the one in the Snap-On tools but honestly other than network problems I don't have to bring it out much. I tend to use my Vantage Pro most of the time just because its convenient. I've been looking at a Pico as well but hard to justify the cost when I already have a couple scopes. If you don't have anything scope wise then the Pico would be my suggestion.
I am having the same issues and have ruled out the dash switch and the plug connector looks good so I am thinking it is the module. I have heard on-line that the red tab like to break on the wiring harness on the module. What is the trick to getting the module unplugged?
Im glad you put this series together thank you! I confirmed its on the truck side just replaced the 7 pin coupler. Problem persists I noticed at 3:59 you mentioned a secondary lock. Mine seems to be missing had the bumper replaced. Dealer said they can't find a part number for the secondary lock. Would that come with the wiring harness? Im assuming missing the secondary lock would contribute to the issue?
The secondary lock is probably only serviced with the harness but it's not critical for proper operation imo. Is it setting any codes?
@@PhillipBailey I appreciate your input, module on the way.
So where is the power module located?
@@davidlewis6929 left of the chassis module above the spare tire.
I know it's a old video, mine is a 2015. Maybe you can tell me where the chsml wire is ? Trying to tap into it for the 3rd brake light on my topper. Thanks
Try Alldatadiy.com for wiring diagrams and connector locations. It's not free but it's pretty reasonable. Alternatively you could tap into the circuit at the brake switch. I'll have a look at the wire colour and get back to you...edit. the brake switch is an input to the bcm which controls the chmsl relay under the hood. The circuit runs through the cab through the instrument panel junction block under left side of dash. Connector x2 and x3 a violet/grey wire. Try to find it there is my recommendation.
@@PhillipBailey found it by calling a local business. Blue and white wire coming out of the BCM.
have a Chevy 3500 wt my service trailer wiring light comes on my dash spelled out with exclamation point, my left blinker and brake light don’t work only left side running lights are brighter on left side also. Tech said he’s getting power on all 7 prongs on my trailer hopkin connecter a snap on code reader saying it’s the brake control module and pressure valve and my code reader says c0800-5A control module not plausible please help
What year is the 3500. As far as I know the lights have nothing to do with the brake control unless you have a bad ground
@@PhillipBailey it is a 2019 , I took apart the Hopkins plug black melted tape or grease was on it wonder if it’s bad one prong kept bending that same prong controlled the left signal
I have a '21 3500 and 02 2500 chevy. I tow daily with the '21 and have gotten the check trailer wiring message on 3 occasions now. The trailer brake control module and 30 amp fuse were changed the 1st time...work fine for 1 month. Took it in and I don't even know what they did to fix, but it wasn't a module replacement. They said it's on the trailer end and printed the bulletin for me to follow. I ordered a new 7 pin connector and just wired it up and I still have the same message on the dash. The fuse is OK. My trailer brakes work just fine with my '02, but at 200k+ miles I don't like hauling with it. What the hell is the issue with this?
Is it setting any codes in the trailer brake control module?
@@PhillipBailey thanks for responding. Not communicating is what the dealership had written.
@@shaymoose17 if its not communicating with their scan tool the it should be under warranty I would think unless you have a ton of mileage on it. I would agree that if tge brakes work on the trailer when towing behind the 02 that the trailer is not the problem. Is the 02 factory trailer brakes or aftermarket controller? If it's aftermarket brake controller then it is more forgiving of issues with the trailer. If the truck is under warranty I'd try a different dealership if possible. You might also try towing a different trailer with the 21 see if you get the same message. There should be a code if that message is coming up.
@@PhillipBailey I haven't towed with any other trailers since the issue had come up. There's 15k miles on the '21 and started using issues around 13k miles. The 02 is an aftermarket controller. I was told the trailer plug is the culprit and the for may be too loose. So I ordered the plug they recommended, hooked up with no success.
@@shaymoose17 ah the aftermarket controller is not as sofistcated as the 21 system and as such may not be as sensitive to an actual problem in the trailer. Given the low mileage on the 21 I would bet the issue is in fact in the trailer. Could be an intermittent break in the trailer brake circuit wire or trailer ground. Does the message on the 21 come up as soon as you plug into your trailer or when you start driving it. It would be best to either tow a different trailer with the 21 or tow your trailer with a newer preferably 21 truck to see what happens.
I only have an issue when I am actually hooked up to my camper. It will jump back and forth between "Check Trailer Wiring" and "Trailer Connected". Funny thing is all the lights work and the trailer brake functions. My truck is a 2016 2500HD with a 6.0 engine. Any ideas?
Other than an intermittent connection at the plug or trailer grounds no sorry. Is the trailer brake module setting any codes?
I’m experiencing the exact same thing with my 2016 Silverado when towing. Any updates on this issue? Thanks.
hi Phillip, maybe you can help me please!, i have a 16 sierra 5.3. for unknown reasons, i have power in my trailer hitch all the time now. meaning the pin that powers up the batter in a trailer. that usually turns off when you take the key out of the truck, now theres always power, i have a truck camper and its draining the truck battery, it didnt do that before
I'm pretty sure that auxiliary power feed is live all the time. Older camper vehicles used to use two batteries under the hood with an isolator. Ill have a look at the circuit and get back to you here.
Just looked at the schematic and the auxiliary feed come from a 30amp maxi fuse that is hot all the time. Something is on in the trailer or if it has a battery in the trailer might be a bad cell in it. Not sure how new the trailer is. Do you have a TV plugged into a 12 volt source in the trailer. Even if its off the inverter in it will draw power. Hope this helps
Hi Phillip. I have a 2021 GMC Sierra AT4. Without any trailer attached I get check trailer lights, disconnect etc error messages constantly. I even detached the connector to the 7 pin and still am getting all the check trailer lights and disconnect messages. Connections are clean and dry and in good shape with only 6000 miles on the truck. Any thoughts would sure be appreciated! Thank you.
Isn't it still under warranty? You need to scan the system for codes and refer to the appropriate troublemaker chart. There are many things that can generate the dash message but need the code/s to proceed.
@@PhillipBailey Thank you Phillip!
Similar problem, I'd like to know if you can help me with mine. Trying to troubleshoot but not sure on some issues. Let me know if you would be willing to help me out. TIA
For some reason I never got this notification so I never responded. Hope you got it resolved.
Happy to see this video I will get that module for mine today thanks
Does this module control the turn signals too, my 2014 there is no power coming out the connector for right turn signal?
I don't believe it does. The right turn signal brake circuit is supplied from the KR63R relay in the underhood fuse center. Check for power at fuse F17 with the signal on or brake applied. It is fused separate from the other circuits. If that is good then other than the connections under the fuse center there is no other test points of connectors til you get to the trailer plug itself. Unplug the back of it and check there. Should be a Green/Violet wire to pin D. HTH
Okay, thanks.
Hey boss, how many volts dc are we suppose to read from ground to blinkers when on?
If you are measuring voltage at one of the turn signal circuits and ground with it on you should see a pulsing battery voltage in sync with the signal lights flashing. Hope this is what you're asking...
@@PhillipBailey thank you for the quick response. I’m having issues with my 2014 GMC Sierra causing the trailer lights to go crazy, any way that you could help? I’d greatly appreciate it
What is the part number for trailer module
23337305 is the number shown at 3:43. Thanks for watching...
Looking forward into your videos with the 19.4 update. I think I’ll eventually get mine to that point hopefully mid year. Im itching really bad for a pico.
I agree that the Pico is a superior scope to the one in the Snap-On tools but honestly other than network problems I don't have to bring it out much. I tend to use my Vantage Pro most of the time just because its convenient. I've been looking at a Pico as well but hard to justify the cost when I already have a couple scopes. If you don't have anything scope wise then the Pico would be my suggestion.
What if I don't have a scan tool to clear the codes
If the problem is corrected the code should eventually clear on its own. You could try disconnecting the battery for awhile. That might work.
I have in my Chevrolet silverado a 7 pole blade , one is not working the electric brakes , did you know what can be ?
Check the 30amp fuse in the underhood fuse panel first. If that's good you will need a full feature scan tool to scan the system for codes.
I am having the same issues and have ruled out the dash switch and the plug connector looks good so I am thinking it is the module. I have heard on-line that the red tab like to break on the wiring harness on the module. What is the trick to getting the module unplugged?
No real trick, try cleaning with compressed air first before trying to unlatch. The plastic does get brittle with age though.
@@PhillipBailey Thank you.