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.
Step 1: Pop the Hood Release the hood latches and secure the hood in the upright position.
Step 2: Find the Black Box Look at the firewall (the wall between the engine and the cab) on the driver’s side. You will see a large black plastic box with a grey lid. It usually has two metal release clips on the sides.
Step 3: Remove the Lid Unlatch the two metal clips and lift the lid. Pro tip: Look on the underside of the lid. Freightenger is good about printing the diagram right there on the plastic.
Step 4: Identify the Exact Fuses For a 2019 Cascadia, you are looking for three specific fuses, usually grouped together:
Note: Some PDM layouts use slot #63 for the trailer stop lamp circuit.
If you replace the fuse and it blows immediately the second you plug in the trailer, you have a short in the trailer wiring (likely a pinched wire or corroded pigtail). If the fuse blows without the trailer plugged in, the issue is in your truck's 7-way socket or the chassis harness.
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.
To access:
Here you will find:
If you want, I can list likely fuse/relay label names from a typical 2019 Cascadia fuse diagram or guide you through testing specific pins on the 7-pin connector.
(Additionally suggested searches available.)
Finding the fuse for trailer lights on a 2019 Freightliner Cascadia
depends on whether you have the classic body or the "New Cascadia" (P4) model, as the locations changed significantly during that production year. Key Locations for Trailer Light Fuses
For most 2019 models, the fuses and relays are split between three main areas:
Passenger Side Dash (Main Location): The primary fuse panel is behind the glove box or a "pull-off" panel in front of the passenger seat. To access it: Open the glove box or pull the panel marked "PULL".
You may need a T-25 Torx bit for older configurations, but many 2019 models use simple snap-on covers. 2019 freightliner cascadia trailer light fuse location
A detailed diagram is usually printed on the inside of the cover.
SAM Chassis (Under the Hood): If you are missing marker lights, check the SAM Chassis module. This is located on the driver-side firewall inside the engine compartment. On some newer 2019 units, this module manages the trailer lights through computer logic rather than traditional individual fuses.
Vehicle Power Distribution Module (VPDM): Located under the passenger-side dash cover or beneath the passenger seat. This panel contains high-amp fuses and main power relays. Troubleshooting Common Light Issues New 2019 Freightliner Cascadis Truck Fuse & Relay Location
2019 Freightliner Cascadia , the trailer light "fuse" location is actually a shift in technology from older models. Instead of a traditional dedicated fuse box on the driver-side firewall, this model often uses the SAM (Signal Detect and Actuation Module) Chassis systems to manage trailer power. The Story of the "Missing" Fuse Box
Imagine a driver pulling over at a rest stop because their trailer marker lights just quit. They open the hood, looking for that familiar black box on the driver-side firewall that every Cascadia they've ever driven had. They find nothing but empty space.
In the 2019 "New Cascadia" (P4 model), Freightliner moved and modernized the electrical system: The Main Power Distribution Module (PDM):
Under the hood on the passenger-side firewall, there is a red box. This contains major power fuses (including some that supply the SAM modules) but not individual trailer light fuses. The Interior Fuse Panel:
Behind a "pull" panel on the passenger-side dash, you'll find the primary fuse and relay compartment. While this houses many cab functions, the trailer lights are often handled by the SAM Chassis The Computerized "Reset": If your trailer lights are out but the
On many 2019 models, the trailer light circuits are computer-controlled. If there is a short in the trailer wiring, the system "trips" the circuit internally. Instead of replacing a blown fuse, you often just need to fix the short and cycle the key
(turn the truck off and back on) to reset the electronic relay. Where to Check if Lights are Out Passenger-Side Dash:
Pull the panel marked "pull" in front of the passenger seat. Check for any blown fuses related to "Trailer Power" or the "SAM" modules. Passenger-Side Firewall (Under Hood): Open the red PDM box. Look for
, which is frequently associated with trailer power or ABS issues in these newer setups. SAM Chassis Location:
On some configurations, this module is located under the hood on the firewall or near the steering rod. The Glove Box:
Some fuses and relays are accessible by removing the glove box (requires a T-25 Torx driver). If you're still having trouble, are you seeing any specific fault codes on your dash display? Freightliner Trailer ABS Fuse is the Problem!
Next to those fuses, you will find a relay labeled "TRAILER LIGHT" or "TLM" (often position R12 or R14). If the relay fails, fuses won’t matter. Swap it with an identical relay (like the horn relay) to test.
If your turn signals are not working on the trailer: Note: Some PDM layouts use slot #63 for