Service: Trailer Brake

[kalangeberg]

Need some help on this. I have a 2015 3500 that I've been troubleshooting for the past several weeks. I keep getting the Service: Trailer Brake message on the console. What I've done so far is replaced the dash controller switch, replaced the brake controller, replaced both the plug on the truck wiring harness and the connection on the bumper. I've tested all of the fuses under the hood and both sides of the dash. Even after all of that it appears I'm not getting power on the blue line to the back of the truck. Any help would be greatly appreciated.

[rav3]

Youtube is your friend. Several video's there. Maybe one might help you

[MikeBMW]

11 minutes ago, kalangeberg said:

Need some help on this. I have a 2015 3500 that I've been troubleshooting for the past several weeks. I keep getting the Service: Trailer Brake message on the console. What I've done so far is replaced the dash controller switch, replaced the brake controller, replaced both the plug on the truck wiring harness and the connection on the bumper. I've tested all of the fuses under the hood and both sides of the dash. Even after all of that it appears I'm not getting power on the blue line to the back of the truck. Any help would be greatly appreciated.

I had that on my 1500 a little while ago.

I opened the fuse box in the engine area, removed and re-seated the trailer brake fuse (it's fairly large). Fixed the issue.
Not sure about a 3500.
Might want to ask here:
https://www.gm-trucks.com/forums/forum/188-2015-2019-silverado-sierra-hd-troubleshooting/

[kalangeberg]

Yep, did that. Pulled the fuses and checked for burnt ones. All test out ok.

[kalangeberg]

1 hour ago, rav3 said:

Youtube is your friend. Several video's there. Maybe one might help you

Went through most of the videos there and did do some of them even replaced the controller switch.

[mikeyk101]

Did you do a check to see if there are any codes?

[kalangeberg]

I did not hook up an OBD to it, but I did disconnect the battery and let it sit over night. The status message still came up after reconnecting the battery.

15 hours ago, mikeyk101 said:

Did you do a check to see if there are any codes?

[mikeyk101]

Might be a good idea to check for codes before trying to throw any more parts at it.

[asilverblazer]

What have you checked on the trailer?

 

The brake output wire goes from the trailer plug to each hub on the trailer, each hub is daisy chained together. The other wire in the hub is ground (doesn't matter which one). Make sure those grounds are good, and no other wiring issues.

 

Make sure trailer is grounded to the truck - through the plug and hitch ball and if the hitch ball and coupler are old drive it a while to rub the rust off and get a clean connection there too.

[kalangeberg]

Good thought. I have a faitlrly new hitch. I just bought it about a year ago. Also I use the electrical grease on the it. Besides that, the error message comes up regardless whether I'm hooked to a trailer or not. But I think your on the right track. I just can't seem to get power on the blue or brake line to the back. Another person suggested that it has to be in a relay somewhere. However none of the relays specifically refer to the brake controller.

[asilverblazer]

1 hour ago, kalangeberg said:

...the error message comes up regardless whether I'm hooked to a trailer or not...

 

I just can't seem to get power on the blue or brake line to the back...

I think as long as the error is there, you won't get any power on the the brake output wire. 

 

I would start inspecting the wiring at the rear, especially the junction block behind the rear bumper. Pull the connectors and check for corrosion.

[asilverblazer]

Circuit/System Description

The K38A Chassis Control Module-Auxiliary receives inputs from the K133 Trailer Brake Power Control Module; these inputs are used to determine trailer connection and the amount of voltage supplied to the trailer brakes.

Conditions for Running the DTC

• Ignition ON.
• Battery voltage is 9–18 V.
• The module is powered up and completes initialization.

Conditions for Setting the DTC

C111B 03

The trailer brake power control module detects a voltage below a calibrated threshold on the battery positive voltage circuit.

C111B 07

The trailer brake power control module detects a voltage above a calibrated threshold on the battery positive voltage circuit.

C111B 5A

The trailer brake power control module monitors the battery positive voltage circuit.

C1595 00

The trailer brake power control module detects a short to ground, open or a short to voltage on the trailer brake control signal circuit.

C1596 01

The trailer brake power control module detects a short to voltage in the trailer brake enable signal circuit.

C1596 02

The trailer brake power control module detects a short to ground or an open in the trailer brake enable signal circuit.

C1114 00

The trailer brake power control module detects a short to ground, open, a short to voltage or a plausibility failure on the trailer brake output circuit.

For symptom byte information, refer to Symptom Byte List

Action Taken When the DTC Sets

C111B 03, C111B 07, C111B 5A

• The trailer brakes will be disabled as long as the fault is present.
• The driver information center (DIC) will display a Service Trailer Brake System message as long as the fault is present.

C1595 00, C1595 01, C1595 02, C1114 00

• The trailer brakes will be disabled for the remainder of the ignition cycle.
• The DIC will display a Service Trailer Brake System message for the remainder of the ignition cycle.

Condition for Clearing the DTC

• The conditions for setting the DTC are no longer present.
• The trailer brake power control module clears the history DTC when a current DTC is not detected in 40 consecutive drive cycles.

Diagnostic Aids

• The procedures used in this document are written to diagnose a concern with the customer’s vehicle with no trailer connected. A concern with the customer’s trailer may be the actual cause for a DTC setting or a circuit fault.
• Some customers may experience an intermittent “Check Trailer Wiring” message and/or a “Service Trailer Brake” message with DTC C1114. These concerns may be caused by a poor connection at the 7–way trailer connector. There are several manufacturers of 7–way (trailer side) connectors and many do not comply with the Society of Automotive Engineers (SAE) standard specifications. Some 7–way (trailer side) connector plugs may not properly engage the truck’s 7–way connector socket and cause open circuits. Also, they may cause deformation and excessive wear of the terminals on the truck’s 7–way connector socket. Over time, this will lead to poor terminal tension between the 7–way (trailer side) connector plug and the truck’s 7–way connector socket. Since the trailer brake control module is always monitoring the vehicle and trailer circuits/components, a poor connection at the 7–way connector may cause a “Check Trailer Wiring” message on the driver information center.
• Engineering has recommended the use of Pollak Heavy Duty 7–way (trailer side) connector plugs. Pollak is the Original Equipment Manufacturer (OEM) of the truck’s 7–way connector socket. The use of a Pollak Heavy Duty 7–way (trailer side) connector plug will ensure proper fit when the two connectors are mated.
• If the truck’s 7–way connector socket terminals are deformed or have excessive wear, it will be necessary to replace the truck side connector (use Genuine GM Parts) along with the trailer’s 7–way connector plug using Pollak HD connector plugs.
• Refer to PIT5311 for additional information.

Circuit/System Verification

1. Ignition ON.
2. Verify that DTCs U1505, U1556, U2504, P2534, P2535, or any other communication DTCs are not set.
   • If any of these DTCs are set
     Refer to Diagnostic Trouble Code (DTC) List - Vehicle.
    
   • If none of these DTCs are set
   
   
3. Verify the Service Trailer Brake System message is not displayed in the driver information center
   • If the Service Trailer Brake System message is displayed and the customer’s trailer is connected to the vehicle
    
   1. Disconnect the customer’s trailer.
   2. Verify the Service Trailer Brake System message is not displayed in the driver information center.
      • If the Service Trailer Brake System message is not displayed after disconnecting the customer’s trailer, the circuit fault causing the DTC to set is located in the customer’s trailer wiring harness. This is not diagnosed in service information, nor is it covered by GM warranty.
       
      • If the Service Trailer Brake System message is displayed after disconnecting the customer’s trailer
      
      
   3. Refer to Circuit/System Testing.
    
   • If the Service Trailer Brake System message is displayed and the customer’s trailer is not connected to the vehicle
     Refer to Circuit/System Testing.
    
   • If the Service Trailer Brake System message is not displayed and the customer’s trailer is available
   
   
4. Verify the customer’s trailer connection is recognized with a Trailer Connected message in the driver information center.
   • If the Trailer Connected message is not displayed when the customer’s trailer is connected to the vehicle
     Refer to Circuit/System Testing.
    
   • If the Trailer Connected message is displayed when the customer’s trailer is connected to the vehicle
   
   
5. All OK.

Circuit/System Testing

Note:

• You must perform the Circuit/System Verification before proceeding with the Circuit/System Testing.
• The following diagnostic procedure is for factory installed components and wiring on the customer’s vehicle. It will not diagnose a concern with the components and wiring on the customer’s trailer.
• The following diagnostic procedure is based on not having a trailer connected to the vehicle.
• Refer to PIT5311 for additional information before using this diagnostic procedure.

1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the K133 Trailer Brake Power Control Module. It may take up to 2 min for all vehicle systems to power down.
2. Test for less than 10 Ω between the ground circuit terminal 9 and ground.
   • If 10 Ω or greater
    
   1. Ignition OFF.
   2. Test for less than 2 Ω in the ground circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, repair the open/high resistance in the ground connection.
      
      
       
    
   • If less than 10 Ω
   
   
3. Ignition ON.
4. Verify a test lamp illuminates between the B+ circuit terminal 1 and ground.
   • If the test lamp does not illuminate and the circuit fuse is good.
    
   1. Ignition OFF, remove the test lamp.
   2. Test for less than 2 Ω in the B+ circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, verify the fuse is not open and there is voltage at the fuse.
      
      
       
    
   • If the test lamp does not illuminate and the circuit fuse is open
    
   1. Ignition OFF, remove the test lamp.
   2. Test for infinite resistance between the B+ circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance, replace the K133 Trailer Brake Power Control Module.
      
      
       
    
   • If the test lamp illuminates
   
   
5. Ignition OFF, disconnect the harness connector at the K38A Chassis Control Module-Auxiliary, ignition ON.
6. Test for less than 1 V between the signal circuit terminals listed below and ground:
   • K133 Trailer Brake Power Control Module signal circuit terminal 2
   • K133 Trailer Brake Power Control Module signal circuit terminal 5
   • K133 Trailer Brake Power Control Module signal circuit terminal 8
   • K133 Trailer Brake Power Control Module signal circuit terminal 12
   • K133 Trailer Brake Power Control Module signal circuit terminal 14 (if equipped with this wire)
    
   • If 1 V or greater
     Repair the short to voltage on the circuit.
    
   • If less than 1 V
   
   
7. Ignition OFF.
8. Test for infinite resistance between the signal circuit terminals listed below and ground:
   • K133 Trailer Brake Power Control Module signal circuit terminal 2
   • K133 Trailer Brake Power Control Module signal circuit terminal 5
   • K133 Trailer Brake Power Control Module signal circuit terminal 8
   • K133 Trailer Brake Power Control Module signal circuit terminal 12
   • K133 Trailer Brake Power Control Module signal circuit terminal 14 (if equipped with this wire)
    
   • If less than infinite resistance
     Repair the short to ground on the circuit.
    
   • If infinite resistance
   
   
9. Test for less than 2 Ω between the signal circuit terminals listed below:
   • K133 Trailer Brake Power Control Module signal circuit terminal 2 and the K38A Chassis Control Module-Auxiliary signal circuit terminal 23
   • K133 Trailer Brake Power Control Module signal circuit terminal 5 and the K38A Chassis Control Module-Auxiliary signal circuit terminal 22
   • K133 Trailer Brake Power Control Module signal circuit terminal 12 and the K38A Chassis Control Module-Auxiliary signal circuit terminal 30
   • K133 Trailer Brake Power Control Module signal circuit terminal 14 and the K38A Chassis Control Module-Auxiliary signal circuit terminal 17 (if equipped with this wire)
    
   • If 2 Ω or greater
     Repair the open/high resistance in the circuit.
    
   • If less than 2 Ω
   
   
10. Test for less than 2 Ω between the K133 Trailer Brake Power Control Module signal circuit terminal 8 and the Electric Brakes terminal in the trailer brake harness connector in the rear bumper. Refer to the diagram on the trailer brake harness connector cover for the terminal location.
    • If 2 Ω or greater
      Repair the open/high resistance in the circuit.
     
    • If less than 2 Ω
    
    
11. Test or replace the K133 Trailer Brake Power Control Module.
12. Verify the DTC does not set while operating the vehicle within the Conditions for Running the DTC.
    • If the DTC sets
      Replace the K38A Chassis Control Module-Auxiliary.
     
    • If the DTC does not set
    
    
13. All OK.

[kalangeberg]

Wow! OK, thank you for all of this info. I'm going to go down through the list. I know exactly where the module is and will pull the plug and ohm it out and see what I can come up with. Thanks again for this info, I appreciate it.

[mikeyk101]

Take a look at page 2 of this thread by @NWI Denali:

 

It was discovered that the wiring harness for trailer brake wiring on rail near rear wheel had rubbed through and needed to be repaired. Something to look at...

 

[NWI Denali]

1 hour ago, mikeyk101 said:

Take a look at page 2 of this thread by @NWI Denali:

 

It was discovered that the wiring harness for trailer brake wiring on rail near rear wheel had rubbed through and needed to be repaired. Something to look at...

 

Yes, especially seeing as you have replaced all the other parts as well like I did, trace and check your harness