Check underneath the drivers door in the harness along the frame. I work at a Chevy dealer in Michigan and I have found the wire corroded there several times.
Thank you very much for all info in the video , I have exactly same issue. And swapped trailer brake adjuster and trailer plug between 2 of my trucks . All works . Was about to order brake control module then came across your video . Long story short i end up splicing 1 and 25 together , checked that no power present there when truck is shut off and no more error. I know it’s not proper repair , but it works and if I blow something so be it lol , as long as I don’t see that message on the screen ! Thank you again !
One of the circuits I believe to pin 1 is hot all the time pin 25 is switched with key on. Jumping them may cause a parasitic draw as it could backfeed. Some possibilities...
Geez wish I would have found this video a month ago been hassling with this for the last month changing the controller and the rear module just checked the 30 amp fuse and it was burnt out 😅 dammm. But thanks to your video I was able to figure it out. Thanks
I like the way you go about diagnosing. I have a 15 that’s not even giving a communication code it’s like it don’t exist. When I click on trailer brake module it just says no communication. Btw I like that scan tool
There are several options for the trailer brake control. This one uses the auxiliary chassis control module as the trailer brake control module. If I tried to select the trailer brake control module I would get no communication with it. Need to select auxiliary chassis control module.
Thanks, I’m still unfortunately working on this one. I can’t get gds to communicate with chassis control module now. It was communicating with chassis module but I installed. Trailer module and now the chassis module is not communicating. Even going back to plugging the old one back up. There is so much dirt under this thing you can’t even fart with it getting in your eyes
@dreece2000 can you test termination resistance of the can bus at pins 6 and 14 of the DLC battery disconnected. It should be 60 ohms +/- 2. If it reads around 120 you have an open in the network. ABS modules are common to fail and take down the bus. If you unplug the ABS module and identify the forward bus pins it should measure 120 ohms and the pins going back should also measure 120 ohms. There is a resistor in the harness at the back that sometimes fails. If you have a lab scope you can look at network activity at the chassis control module bus pins too.
@@PhillipBailey i will do that when I get back to it. Thanks for the info. This is one of them customer standing over you hindering you to death trucks.
I hope this isn't what's wrong with mine. However, I'm not getting continuous alarms. Only the 1 time when I start it and hit ok. I don't get it again until I start it back up. I replaced the Controller in cab and that was not successful. Going to try replacing the plug itself and go from there. Thank you for the video.
I’m having an issue between the Chassis Control Module and the Brake Control Module on a 2018 Suburban. Throws a bunch of U codes, Reduced Power Steering, Service Trailer Brake, ABS, Stabilitrak. Lost a wire. Can’t figure out which one. I’ve seen where apparently a transistor right in that neighborhood can go bad. Moisture seems to exacerbate my problem. Very frustrating.
Try measuring terminating resistance between pins 6 and 14 of the DLC with the battery disconnected. Should be 60 ohms. I gather you don't have a scope to look at can bus signals. Which modules don't communicate?
@@PhillipBailey After physically checking the ECM, the Body Control Module, the Brake Control Module, the Chassis Control Module, and the Trailer Brake Control Module for anything obvious and connections, and checking the harness everywhere I could, saw a couple bulletins on 5986 Circuit, and reprograming the PSCM, I gave up and took it to the dealership. They diagnosed and found “a bad wire between Chassis Control and Brake Control”. I asked which wire and the guy said he though the tech said K 12. They want $1k to run a new wire. Unfortunately I don’t know exactly which wire. But am going to try to find out and save myself the money. We got some snow and the roads were wet today and after a week of almost nothing in dry conditions it’s been yelling at me all day.
@HuntMountain06 I believe 5986 is referred to as the Serial Data Wakeup circuit which comes from the BCM and is basically the ignition wakeup voltage to various modules. I'm not sure which module is K12 but I will check. It would be nice if you knew what fault codes were being generated. If that circuit is shorted to ground it will likely take down communication with multiple modules.
Actually the circuit 5986 does not appear to exist. The wire I thought you were referring to is 5985. K12 does not appear to be a valid module number either.
@@PhillipBailey codes are U0121-00, U0415-00, U0428-71, U0415-71, U0401-71, U0422-00. I didn’t get a chance to pull codes today weather was uncooperative. Wet roads seem to really set everything off though. Going to drop the spare tire tomorrow or Thursday and poke around the chassis control and trailer brake control and see if I can kind find my wire. Maybe spray it with a house and catch it lighting everything up like a Christmas Tree again. Would be great to have a specific wire color to aim for.
Nice job! Working upside down and backwards is always frustrating. You are a more patient than me. Very helpful video. Thanks for posting
Check underneath the drivers door in the harness along the frame. I work at a Chevy dealer in Michigan and I have found the wire corroded there several times.
Thank you for the info Michael! Mine was broken…red with white stripe. Code is gone
Do you mean underneath the door sill? Or under the truck?
Thank you very much for all info in the video , I have exactly same issue. And swapped trailer brake adjuster and trailer plug between 2 of my trucks . All works . Was about to order brake control module then came across your video . Long story short i end up splicing 1 and 25 together , checked that no power present there when truck is shut off and no more error. I know it’s not proper repair , but it works and if I blow something so be it lol , as long as I don’t see that message on the screen ! Thank you again !
One of the circuits I believe to pin 1 is hot all the time pin 25 is switched with key on. Jumping them may cause a parasitic draw as it could backfeed. Some possibilities...
Your a great service tec. Thanks for all your time showing us your talents..Have to learn patient's for sure. Thumbs up..Learning alot 👍😎
Great video Phil. Keep them coming
Geez wish I would have found this video a month ago been hassling with this for the last month changing the controller and the rear module just checked the 30 amp fuse and it was burnt out 😅 dammm. But thanks to your video I was able to figure it out. Thanks
Always start with the fuses but hindsight is 20/20.
GREAT VIDEO AND THANKS FOR YOUR TIME ,,, FINDING OPEN WIRES CAN BE TUFF SO HOPE TO SEE MORE OF YOUR GREAT DIAGNOSTIC VIDEOS 👍👍👍
Great diag. Going to dive into mine tomorrow
I like the way you go about diagnosing. I have a 15 that’s not even giving a communication code it’s like it don’t exist. When I click on trailer brake module it just says no communication. Btw I like that scan tool
There are several options for the trailer brake control. This one uses the auxiliary chassis control module as the trailer brake control module. If I tried to select the trailer brake control module I would get no communication with it. Need to select auxiliary chassis control module.
Thanks, I’m still unfortunately working on this one. I can’t get gds to communicate with chassis control module now. It was communicating with chassis module but I installed. Trailer module and now the chassis module is not communicating. Even going back to plugging the old one back up. There is so much dirt under this thing you can’t even fart with it getting in your eyes
@dreece2000 can you test termination resistance of the can bus at pins 6 and 14 of the DLC battery disconnected. It should be 60 ohms +/- 2. If it reads around 120 you have an open in the network. ABS modules are common to fail and take down the bus. If you unplug the ABS module and identify the forward bus pins it should measure 120 ohms and the pins going back should also measure 120 ohms. There is a resistor in the harness at the back that sometimes fails. If you have a lab scope you can look at network activity at the chassis control module bus pins too.
@@PhillipBailey i will do that when I get back to it. Thanks for the info. This is one of them customer standing over you hindering you to death trucks.
I have 120 ohms with abs plugged or unplugged
Great video, Thanks!
I hope this isn't what's wrong with mine. However, I'm not getting continuous alarms. Only the 1 time when I start it and hit ok. I don't get it again until I start it back up. I replaced the Controller in cab and that was not successful. Going to try replacing the plug itself and go from there. Thank you for the video.
Great video!
That’s what was wrong with mine thank you
I’m having an issue between the Chassis Control Module and the Brake Control Module on a 2018 Suburban. Throws a bunch of U codes, Reduced Power Steering, Service Trailer Brake, ABS, Stabilitrak. Lost a wire. Can’t figure out which one. I’ve seen where apparently a transistor right in that neighborhood can go bad. Moisture seems to exacerbate my problem. Very frustrating.
Try measuring terminating resistance between pins 6 and 14 of the DLC with the battery disconnected. Should be 60 ohms. I gather you don't have a scope to look at can bus signals. Which modules don't communicate?
@@PhillipBailey After physically checking the ECM, the Body Control Module, the Brake Control Module, the Chassis Control Module, and the Trailer Brake Control Module for anything obvious and connections, and checking the harness everywhere I could, saw a couple bulletins on 5986 Circuit, and reprograming the PSCM, I gave up and took it to the dealership. They diagnosed and found “a bad wire between Chassis Control and Brake Control”. I asked which wire and the guy said he though the tech said K 12. They want $1k to run a new wire. Unfortunately I don’t know exactly which wire. But am going to try to find out and save myself the money. We got some snow and the roads were wet today and after a week of almost nothing in dry conditions it’s been yelling at me all day.
@HuntMountain06 I believe 5986 is referred to as the Serial Data Wakeup circuit which comes from the BCM and is basically the ignition wakeup voltage to various modules. I'm not sure which module is K12 but I will check. It would be nice if you knew what fault codes were being generated. If that circuit is shorted to ground it will likely take down communication with multiple modules.
Actually the circuit 5986 does not appear to exist. The wire I thought you were referring to is 5985. K12 does not appear to be a valid module number either.
@@PhillipBailey codes are U0121-00, U0415-00, U0428-71, U0415-71, U0401-71, U0422-00. I didn’t get a chance to pull codes today weather was uncooperative. Wet roads seem to really set everything off though. Going to drop the spare tire tomorrow or Thursday and poke around the chassis control and trailer brake control and see if I can kind find my wire. Maybe spray it with a house and catch it lighting everything up like a Christmas Tree again. Would be great to have a specific wire color to aim for.
wow not easy .tks