Common Customer Trailer-Side Faults When Using the Trailering App

The 2019-2022 Silverado 1500, Sierra 1500; 2020-2022 Silverado 2500HD/3500HD, Sierra 2500HD/3500HD; and 2021-2022 Tahoe, Suburban, Yukon and Escalade offer a number of systems designed to help make towing easy. (Fig. 9) The in-vehicle trailering app (RPO U1D), for example, offers customization options for several trailer profiles, additional cameras, and trailer tire pressure and temperature monitoring.


Fig. 9


Each vehicle system requires the proper operation of the trailer-side systems in order to work correctly. Conditions such as inoperative trailer lighting or trailer detection or intermittently flashing trailer lights while the vehicle is off may be the result of a poor connection on the customer’s trailer. If any trailer-related issues are found, it’s important to advise customers about the trailer wiring, connectors and trailer lighting. Trailer issues are not covered under the New Vehicle Limited Warranty.


Trailer Lighting

When a trailer is connected to the vehicle, the Trailer Lamp Control Module on the vehicle responds to the operator’s lighting controls by applying voltage to the appropriate control circuit to the trailer connector of the vehicle. When the electrical connector from the trailer is plugged into the trailer connector of the vehicle, the voltage from the vehicle is then applied to the appropriate circuit on the trailer and the corresponding lamp on the trailer will illuminate. Fuse F74UA and F82UA are the power supply fuses to the Trailer Lamp Control Module. If a fuse is blown, an electrical fault likely exists on the trailer.

If it’s necessary to determine the proper operation of the Trailer Lighting Control Module, connect the EL-52641 Trailer Simulator Test Tool to the vehicle’s 7-way connector. (Fig. 10) The Trailer Lighting Control Module will detect the test tool and enable the trailer lighting outputs.


Fig. 10


Trailer Wiring Faults

Some common electrical failures found on trailers include loose connections, faulty ground circuits and water intrusion.

TIP: On 2021-2022 Tahoe, Suburban, Yukon, Escalade and 2022 Silverado 1500 and Sierra 1500 models, it is normal for the Driver Information Center to display a Check Trailer Wiring message when the trailer is disconnected from the vehicle while the ignition is in the Run position.

For any intermittent electrical issues on the trailer, check the trailer connector as well as the trailer lamp assemblies for a loose or broken connection. Wire nuts should not be used to service trailer wiring. Wire nuts are not properly sealed for automotive use and will allow moisture and debris into the electrical connection.

Also check for corroded or weak ground connections. Ground circuits are usually connected to the frame of the trailer using a screw or bolt. A faulty ground connection will not allow the flow of electricity through the circuit, resulting in defective lamp operation.

Lamps and wiring on boat trailer also may be damaged by water intrusion if not sealed properly. Water intrusion will usually lead to an electrical fault on the trailer and cause a high-current condition, resulting in a blown fuse.


Trailering App

The available in-vehicle trailering app incorporates the functions of several vehicle systems in order to provide trailer lighting diagnostics, trailer tire pressure/temperature monitoring and trailer braking with an Integrated Trailer Brake Controller.

The trailering system consists of the following systems:

  • Trailer lighting
  • Trailer brakes
  • Trailer battery charging system
  • Trailer detection
  • Trailer tire pressure monitoring system
  • Trailer theft detection

Trailer lighting can be verified using the light testing feature on the trailering app. With the trailer connected to the vehicle, start the vehicle and select Start Light Test on the app. The trailer tail lamps, trailer turn/stop lamps and trailer backup lamps will turn on and off.

When a trailer is connected with the vehicle ignition off, the Trailer Lighting Control Module will periodically pulse the lighting circuits of the trailer to verify it is still connected. Flashing or flickering lights is a normal condition.

If any trailer connections are lost, a message will appear on the Driver Information Center. Depending on the settings, a Trailer Connected or No Trailer Connected status may be displayed by the trailering app on the infotainment screen. (Fig. 11)


Fig. 11


For additional information about typical trailer-side faults, refer to Bulletin #22-NA-108, Bulletin #22-NA-109 and Bulletin #22-NA-111.


– Thanks to David MaGillis, Kevin Minor and Hassan Abdallah

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  1. The article has been updated with the correct link.

  2. Neal Shipley says:

    Guess you need to add the link in Para. 2 under Trailering App where it says

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