Peterbilt 389 Marker Lights Not Working [Fixed]

You just started your truck, and you turned on the lights. Every light works in your vehicle, but the marker lights aren’t working.

You just parked this vehicle last night, and it was fine. You might be wondering, what happened? Why are the Peterbilt 389 marker lights not working?

There could be a few reasons, such as tripped circuit breaker or blown fuse, exposed cord, jammed wires, faulty turn signal switch, or broken. These are common problems that can happen in your vehicle and cause this particular problem.

Whatever the reason, we can fix the marker lights problem in your vehicle. 

Let’s see how you can do that!

Marker Lights In Peterbilt 389: Overview

Peterbilt 389 Marker Lights Not Working

The marker lights in your truck, such as Peterbilt 389, are meant to keep you and the other vehicles out of harm’s way.

You can know a few things by seeing the marker lights from far away. You can get an idea of the truck, such as the size or if the truck is big or medium. Besides, those can show directions to where the truck is headed.

The marker lights are very much visible. Especially at night, when the room is dark, and you’re on the road, the lights can help you understand what’s on the opposite side of the room. You can quickly identify the truck or vehicle size from far away.

The wiring and the electric system can be a bit complex in a big truck like Peterbilt 389. The 6-way connector for the taillight is found in the chassis harness at the end of the frame. If no tail lights are available, it will either be fastened to a jumper harness, a tail light, or hooked to the rail.

Sometimes many things can go wrong, and the marker lights might not work. Whatever the reason might be, there are always some solutions. Let’s look into them one by one.

Peterbilt 389 Marker Lights Not Working – Reasons And Fixes

How to fix Peterbilt 389 Marker Lights Not Working

As marker lights are essential, you must get them fixed ASAP. But first, you need to know what could cause the problem. And after that, you can find the solutions to the problem.

But, a few things first;

  • Pull out the bulbs one by one and see if there is any wiring problem.
  • Clean the pigtail connection.
  • Inspect if there is any loose connection in the turn signal switch.
  • Do a full fuse and relay test all over the electric system.
  • There is an ignition switch. See if there is any problem there. If it’s okay, test the power in every fuse there.
  • Check if the lighting module is working fine or not.
  • Check the connector pins.
  • Wiring is the primary problem; check the harness is that’s ok.

Whatever the reason might be, there are always some solutions. Let’s discuss the problems one by one and figure out the answer.

Tripped Circuit Breaker

Having a short circuit can cause many problems, such as marker lights not working. Sometimes, the vehicle needs too much power, and suddenly the truck tries to consume more power from the power source.

As a result, there might be a short circuit somewhere that causes the problem. And for that, probably, all the lights are working fine, but the marker lights are the only ones that are not working.

The solution to this problem is to reset the circuit breaker. That would solve the problem.

Exposed Pigtail Problem

Sometimes the rear pigtail can cause problems. You will find bulbs on the side of your truck, and then there will be LED bulbs on the pigtail of your vehicle.

If you’re running your truck in snow, cold, or rain, that could create a problem. When the pigtails are exposed, that thing could get wet. And we all know what happens after that, fuse bulbs or led bulbs are not working.

When you’re riding the truck on an icy road, it sometimes negatively affects your wiring. As those are made of copper, that can go wrong.

But, you need to electrical contact cleaner. There is a bulkhead plug. You need to pull that out. Don’t forget to clean the pigtail connection.  After that, You just need to buy a new one if the bulb is gone.

Cord Problem

There is a bulb cord or light cord you will find. Pull that out. When you inspect it, you will find a problem with the wiring or the trailer itself.

There’s a problem if there’s a short in the cord area, even when it’s unplugged. You must pull out the entire system and replace it with the new one.

Wiring Problem

Sometimes wiring in the camper is the main culprit for this to happen. If there was a shortage in the system, and the wiring got affected somehow, you need to change that part.

Corroded wires could be the most common place to look for splices inside the wiring harness. With a multimeter, it will be easy to test the bulb and the wiring system if anything is wrong. The wires could sometimes be in lousy shape and corroded against each other.

The wiring could go wrong; if someplace got fried, that part needs to change immediately. If not, you could also affect the other part of the wiring system. So, you must get it fixed ASAP.

Turn Signal Switch Problem

The turn signal switch can go wrong sometimes. You need to fix it if it’s broken, faulty, or gone bad.

Sometimes it might not fix the problem at first. But it will calibrate the problem and fix the circuit itself. Besides, you might need to sand down the electric connection a bit. 

There are electric connections at the tractor side. If there is a wiring or connection problem, you need to fix that.


Are Running Lights The Same As Marker Lights?

No, technically, the running lights and the marker lights are not the same. The running lights are for when you’re driving to see the road. On the other hand, the marker lights are for other drivers from far to see that a truck or vehicle is coming.

What Color Do Marker Lights Need To Be?

Marker lights need to be red, mostly. But bright or dark colors that can be seen from far away are recommended. The lights can also be deep blue, the color you see on police vehicles.

What Are Marker Lights On A Semi Truck?

The marker lights on a semi-truck are meant to send a signal, just like any other truck. From afar, other drivers can understand what types of vehicles are approaching.

Last Words

We hope this article gave you the answer to why the Peterbiltlt 389 marker lights are not working. Hopefully, you will be able to fix your problem.

It’s ok if it feels difficult to resolve this problem at first. Let us know if you have any other questions regarding these issues.

Good luck!

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