oh man thanks so much for this video I found that my 40 amp fuse to the one post was faulty would have never checked the bigger fuses anyway power to trailer brakes is now restored awesome !
so I check that fuse on my 6.0 gas 2008. It was blown. But what surprises me is that one end is positive or hot and the other is negative or ground. When I install the new j fuse it blows instantly.
That fuse feeds battery power to the trailer brake relay on the red/black wire It is at the rear of the truck just in front of the trailer brake module on the inside of the left frame rail. Inspect the wires along the frame for damage if not unplug the relay. If the short is gone with relay disconnected replace the relay. HTH
Thx for the vid..Is there a way to test if it is the relay that's causing the issue? I see a lot of comments on other videos saying they replsced j fuse and relay and still are having issuesMy j fuse is fine, getting power at both posts. I'm getting code c1114
But are you getting power to the pin in the trailer plug. I use a seal beam headlight to test the circuit with a trailer harness connector plugged in. Also check the ground pin . You can also swap the relay to confirm it's not that.
The two studs typically are fused by the appropriate fuse. It's up to the owner as to which one is used for trailer brake. The other stud is likely to feed accessory power to the trailer plug. ( the one with the blue fuse). This often charges a battery in the trailer or runs interior lights etc. HTH
One year later and I’m still dealing with this god forsaken C0845-03 error on my truck. I have access to all data and followed the diag flow chart checking voltage along the pink signal wire and I have good voltage going into the TBCM harness. The next step it suggests is replacing the TBCM which I did and also had it flashed to the truck. My trailer brakes works 95% of the time, but whether I have a trailer on or not every time I take my foot off the brake it dings a DCT at me. Took it in to two diffent people and they said I need a new TBCM. I guess I replace it again? Really at a loss, if I could just bypass the whole system and install an aftermarket I would.
1. At key on, engine off, check for voltage available at the MISC IGN Fuse 42 in the Underhood Electrical Center (UHEC). 2. If voltage is present, go to the Trailer Brake Control Module (TBCM) and check for 12 volts on the Pink wire pin 15. Best to load test this wire with a headlight to confirm no voltage drop problems. 3. If no voltage is present at the TBCM, repair the open in the Pink wire back to the underhood fuse block. 4. If voltage is present, also check for ground on pin 1 Black wire at the TBCM. 5. Check pin 17 Light Blue wire for 10-12 volts key on. This has to be tested with a voltmeter. 6. Check for poor pin connections at the plug to the TBCM. 7. If all the above tests good but code will not clear, then replace and program the TBCM. It's critical to test the power and grounds with a high current test light as a voltage reading on an unloaded circuit is inconclusive. Also pull that fuse and inspect the terminals for corrosion in the fuse box...good luck
Thanks. It’s been a minute but all of these steps sound familiar although I’m not confident the test light I used was a high current and I know I never load tested the pink wire. I’ll run back through it all again with those added details and see what becomes of it. Thanks for your time again
I am not getting any codes but I have the message on my dash. I’ve replaced the controller switch, ITBC, ITBC relay, all the fuses, and my trailer harness I’m the back. I guess there must be something wrong with my software, not sure what’s going on with the truck. I’m using scanXL pro on. 2008 GMC Sierra.
@@The_Brew_Dog if you installed a new trailer brake control module it needs to be programmed to the truck using a J2534 pass through and downloading the software from GM. It's not programmed out of the box. I'd put the original controller back in and restart diagnosis.
@@PhillipBailey ah… wish I had known that prior to doing it. Not sure I still have the old one but that makes sense why I am getting the error that I’m getting. If I don’t have it still does it have to go to the dealership now then?
A conventional test light is adequate for most diagnosis but yes a voltmeter and even a lab scope is needed sometimes. I'm sure there are hundreds of tutorials on using a voltmeter on CZcams. Time to learn...
I bought a new test light on Amazon. It reads both negative and positive ground and also gives a digital voltage readout so when testing the 7 pin you can see the voltage climb as you depress the brake pedal. This is the best trailer brake video and I’ve looked at a bunch.
oh man thanks so much for this video I found that my 40 amp fuse to the one post was faulty would have never checked the bigger fuses anyway power to trailer brakes is now restored awesome !
Glad you figured it out.
Thanks, man help me out big-time
Would love to have your diagnostic reader. I have the small one.
so I check that fuse on my 6.0 gas 2008. It was blown. But what surprises me is that one end is positive or hot and the other is negative or ground. When I install the new j fuse it blows instantly.
You have a short to ground on that circuit with the fuse blowing. Is it for the trailer brake circuit? Is this with a trailer connected?
That fuse feeds battery power to the trailer brake relay on the red/black wire
It is at the rear of the truck just in front of the trailer brake module on the inside of the left frame rail. Inspect the wires along the frame for damage if not unplug the relay. If the short is gone with relay disconnected replace the relay. HTH
Thx for the vid..Is there a way to test if it is the relay that's causing the issue? I see a lot of comments on other videos saying they replsced j fuse and relay and still are having issuesMy j fuse is fine, getting power at both posts. I'm getting code c1114
But are you getting power to the pin in the trailer plug. I use a seal beam headlight to test the circuit with a trailer harness connector plugged in. Also check the ground pin . You can also swap the relay to confirm it's not that.
👍
Where is the TBCM located.
what is the 2 stud for? the one of the blue relay?
The two studs typically are fused by the appropriate fuse. It's up to the owner as to which one is used for trailer brake. The other stud is likely to feed accessory power to the trailer plug. ( the one with the blue fuse). This often charges a battery in the trailer or runs interior lights etc. HTH
One year later and I’m still dealing with this god forsaken C0845-03 error on my truck. I have access to all data and followed the diag flow chart checking voltage along the pink signal wire and I have good voltage going into the TBCM harness. The next step it suggests is replacing the TBCM which I did and also had it flashed to the truck. My trailer brakes works 95% of the time, but whether I have a trailer on or not every time I take my foot off the brake it dings a DCT at me. Took it in to two diffent people and they said I need a new TBCM. I guess I replace it again? Really at a loss, if I could just bypass the whole system and install an aftermarket I would.
1. At key on, engine off, check for voltage available at the MISC IGN Fuse 42 in the Underhood Electrical Center (UHEC).
2. If voltage is present, go to the Trailer Brake Control Module (TBCM) and check for 12 volts on the Pink wire pin 15. Best to load test this wire with a headlight to confirm no voltage drop problems.
3. If no voltage is present at the TBCM, repair the open in the Pink wire back to the underhood fuse block.
4. If voltage is present, also check for ground on pin 1 Black wire at the TBCM.
5. Check pin 17 Light Blue wire for 10-12 volts key on. This has to be tested with a voltmeter.
6. Check for poor pin connections at the plug to the TBCM.
7. If all the above tests good but code will not clear, then replace and program the TBCM.
It's critical to test the power and grounds with a high current test light as a voltage reading on an unloaded circuit is inconclusive. Also pull that fuse and inspect the terminals for corrosion in the fuse box...good luck
Thanks. It’s been a minute but all of these steps sound familiar although I’m not confident the test light I used was a high current and I know I never load tested the pink wire. I’ll run back through it all again with those added details and see what becomes of it.
Thanks for your time again
@Altruisticgerms good luck and let me know what you find
I am not getting any codes but I have the message on my dash. I’ve replaced the controller switch, ITBC, ITBC relay, all the fuses, and my trailer harness I’m the back. I guess there must be something wrong with my software, not sure what’s going on with the truck. I’m using scanXL pro on. 2008 GMC Sierra.
Have you physically tested each circuit at the 7 pole plug?. Load test the ground. I use a car headlight on each circuit.
@@PhillipBailey no, but I will. Got a new bi directional scanner and the code I’m getting on it is CO56E ECU Not Programmed/Software not calibrated.
@@The_Brew_Dog if you installed a new trailer brake control module it needs to be programmed to the truck using a J2534 pass through and downloading the software from GM. It's not programmed out of the box. I'd put the original controller back in and restart diagnosis.
@@PhillipBailey ah… wish I had known that prior to doing it. Not sure I still have the old one but that makes sense why I am getting the error that I’m getting. If I don’t have it still does it have to go to the dealership now then?
@@PhillipBailey and thank you.
Wish i knew how to use a voltmeter, I know I'm an idiot... just never used one
A conventional test light is adequate for most diagnosis but yes a voltmeter and even a lab scope is needed sometimes. I'm sure there are hundreds of tutorials on using a voltmeter on CZcams. Time to learn...
I bought a new test light on Amazon. It reads both negative and positive ground and also gives a digital voltage readout so when testing the 7 pin you can see the voltage climb as you depress the brake pedal. This is the best trailer brake video and I’ve looked at a bunch.
What software / hardware are you using
I'm using a Snap-on Verus Edge and Snap-on software.