2019 Freightliner Cascadia Trailer Light Fuse Location Online

If your trailer tail lights and side markers are not working, but your brake lights and turn signals are working:

If the fuses/breakers are good, the issue is often corrosion inside the 7-way plug on the back of the truck. Clean the pins and check for a loose ground wire (usually the white wire inside the plug).

Disconnect the trailer. Replace the fuse. Do the truck’s tractor lights work normally? (Test your brake pedal and turn signals using the cab lights). If the tractor lights work fine and the fuse holds without the trailer, the problem is 100% in your trailer’s wiring harness (bad ground, rodent damage, or a shorted LED light).

Many 2019 Cascadias have a second set of trailer-related fuses inside the battery box on the driver’s side frame rail, just behind the front tire. 2019 freightliner cascadia trailer light fuse location

To access:

Here you will find:

If the ABS light on the dash is staying on or the trailer ABS is not powering up: If your trailer tail lights and side markers

+-----------------------------------+
|  [Relay]  [Relay]  [30A]  [30A]   |
|  [15A]    [15A]    [10A]   [--]   |
|  [10A]    [TRL MKR] [15A L] [15A R]|  <-- Trailer lights here
|  [5A]     [10A]     [--]    [10A]  |
+-----------------------------------+

Note: Always verify with your vehicle’s fuse map as minor variations exist between early and late 2019 production.

Guide: Locating the Trailer Light Fuses on a 2019 Freightliner Cascadia

If your trailer lights (running lights, brake lights, or turn signals) have stopped working on your 2019 Freightliner Cascadia, the issue is often a blown fuse or a tripped Breaker. Unlike older trucks where fuses were scattered, the Cascadia centralizes most fuses in the dash. Here you will find: If the ABS light

Here is a step-by-step guide to finding and identifying the correct fuses.

If your trailer lights are out but the ABS light on your dash is also blinking or staying on, you likely have a grounding issue on the trailer itself, not a fuse. However, if the ABS light is off but the markers are dead—stick to Fuse #60.

The 7-way trailer plug on the back of the Cascadia is exposed to road salt, rain, and dirt. Open the plastic spring door on the trailer cord receptacle. Look for green crusties (copper oxide). Corrosion causes a short that will blow your F30 (Marker lights) or F31/F32 (Turn signals) instantly.