Service: Trailer Brake

[Shaduw]

Hi replaced the trailer brake control module and switch and the trailer brake system keeps popping up and so I hook up a scan tool and gave me code for c1117 and I have a 2018 Chevy Silverado 1500 LT I don’t know if I should check the wires or what please help thanks

[mikeyk101]

2 hours ago, Shaduw said:

Hi replaced the trailer brake control module and switch and the trailer brake system keeps popping up and so I hook up a scan tool and gave me code for c1117 and I have a 2018 Chevy Silverado 1500 LT I don’t know if I should check the wires or what please help thanks

Did you happen to go to the beginning of this thread you just posted in and try some of the troubleshooting information? That's where you should probably start.

[asilverblazer]

On 1/17/2025 at 3:10 PM, Shaduw said:

Hi replaced the trailer brake control module and switch and the trailer brake system keeps popping up and so I hook up a scan tool and gave me code for c1117 and I have a 2018 Chevy Silverado 1500 LT I don’t know if I should check the wires or what please help thanks

C1117 00

• The K38A Chassis Control Module-Auxiliary detects a short to ground, open or a short to voltage on the redundant manual apply signal circuit.
• The K38A Chassis Control Module-Auxiliary detects an open on the low reference circuit.

C1117 00

• The manual apply lever located on the trailer brake control panel is disabled as long as the fault is present.
• The trailer brakes will still apply when using the vehicle’s service brake pedal.
• The driver information center will display a Service Trailer Brake System message as long as the fault is present.

Circuit/System Verification

1. Ignition ON.
2. 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
   
   
3. All OK.

Circuit/System Testing

1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the S76 Trailer Brake Control Switch. It may take up to 2 min for all vehicle systems to power down.
2. Test for less than 10 Ω between the low reference circuit terminal 8 and ground.
   • If 10 Ω or greater
   1. Ignition OFF, disconnect the harness connector at the K38A Chassis Control Module-Auxiliary.
   2. Test for less than 2 Ω in the low reference circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the K38A Chassis Control Module-Auxiliary.
      
       
    
   • If less than 10 Ω
3. Ignition ON.
4. Test for 4.8–5.2 V between the 5 V reference circuit terminal 3 and ground.
   • If less than 4.8 V
   1. Ignition OFF, disconnect the harness connector at the K38A Chassis Control Module-Auxiliary.
   2. Test for infinite resistance between the 5 V reference circuit and ground.
      • If less than infinite resistance, repair the short to ground on the circuit.
      • If infinite resistance
   3. Test for less than 2 Ω in the 5 V reference circuit end to end.
      • If 2 Ω or greater, repair the open/high resistance in the circuit.
      • If less than 2 Ω, replace the K38A Chassis Control Module-Auxiliary.
    
   • If greater than 5.2 V
   1. Ignition Off, disconnect the harness connector at the K38A Chassis Control Module-Auxiliary, ignition ON.
   2. Test for less than 1 V between the 5 V reference circuit and ground.
      • If 1 V or greater, repair the short to voltage on the circuit.
      • If less than 1 V, replace the K38A Chassis Control Module-Auxiliary.
      
       
    
   • If between 4.8–5.2V
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:
   • S76 Trailer Brake Control Switch signal circuit terminal 4
   • S76 Trailer Brake Control Switch signal circuit terminal 5
   • S76 Trailer Brake Control Switch signal circuit terminal 6
    
   • 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:
   • S76 Trailer Brake Control Switch signal circuit terminal 4
   • S76 Trailer Brake Control Switch signal circuit terminal 5
   • S76 Trailer Brake Control Switch signal circuit terminal 6
    
   • 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:
   • S76 Trailer Brake Control Switch signal circuit terminal 4 and the K38A Chassis Control Module-Auxiliary signal circuit terminal 20
   • S76 Trailer Brake Control Switch signal circuit terminal 5 and the K38A Chassis Control Module-Auxiliary signal circuit terminal 18
   • S76 Trailer Brake Control Switch signal circuit terminal 6 and the K38A Chassis Control Module-Auxiliary signal circuit terminal 21
    
   • If 2 Ω or greater
     Repair the open/high resistance in the circuit.
    
   • If less than 2 Ω
   
   
10. Test or replace the S76 Trailer Brake Control Switch.
11. 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
    
    
12. All OK.

[asilverblazer]

Long story short - I bet it's the switch.