“Trailer Lighting Module Fault” in Ford Trucks: Fixes

Trailer lighting module fault message highlights

• Common reasons:trailer module software problems, 4-pin connector issues
• How to fix:install new software for trailer module, use 7-pin connector
• Possible consequences:distracting message popping up on your dash
• Priority level:Low
• Can you drive?Yes
• DIY repair:Possible
• Repair price range:$100-$250

Also, check my article about the trailer brake module fault in Ford trucks. This may answer several of your questions.

Here's what I will tell you today:

• What does it mean when you see "Trailer Lighting Module Fault"?
• What are the common reasons for this problem?
• What should you immediately do when you see this message?
• Can you drive without properly working trailer lights?

Let's get started!

What does this message mean?

Well, it means that the trailer control module (or the special computer that controls all the functions of the connected trailer) found the problem with the trailer lights. Sometimes, it's just because there is some short circuit in the trailer's electrical system. Or just because one of the light bulbs isn't working.

But, in most cases, your trailer is completely OK. It only means that there are some possible problems with your truck.

When it comes to trailer connection, there are several modules and parts that can cause this message. But later I will tell you more about it.

The important thing to notice is that one or several lights aren't working in your trailer right now. This is important to understand and make possible adjustments to your route or driving style. Sometimes, you will not be able to continue driving at night just because it may not be really safe for you and for other vehicles on the road.

What are the possible causes of trailer light problems?

So, in Ford trucks, these problems can come from the trailer and also from the truck. The first thing you can do is to check whether the trailer is in charge. For example, you can connect another trailer to the socket and see if its lights are working and the vehicle doesn't throw the annoying message.

But let's first look at the possible reasons for this problem:

1. Short circuit in your trailer

If yesterday everything was OK with this trailer, it doesn't mean that today it can't develop a problem. Bad connections, problems with fuses, issues with wet wiring, and some other factors may contribute to problems with electrical chains. Checking the trailer's wiring system is one of the first things you should do to make sure the problem isn't there. You may use a multimeter to check resistance between different pins and see if the trailer's wiring is OK.

It's worth checking the light bulbs because sometimes the trailer control module in your Ford truck may go mad and just throw this error message.

2. Trailer socket in your truck

4-pin connectors are faulty. If you have the 4-pin connector, just buy the 7-pin one and install it. They are interchangeable and any car electrician can install this thing for half an hour. You can even do it yourself after watching a proper tutorial video.

The 4-pin connectors are known to be pretty faulty, lose contact, and throw all kinds of different problems. Actually, in about 90% of cases when truck owners reported the problem with the "Trailer Lighting Module Fault" message, this was connected to the bad connector.

3. Software issues in your Ford truck

There was one serious software update that fixed several problems with the trailer modules. I strongly recommend you go and check the possible updates for the software in your vehicle. If your dealer may offer a newer version, just have it installed.

But if the trailer control module already has the latest version of the software in it, it's most likely you will need some other solutions from my list.

4. Trailer control module issues

One more problem that may cause issues with your trailer lighting is the trailer control module. This is the small computer that operates all the needed functions of the trailer and gets the proper information about your vehicle's operation when the trailer is connected. If this module doesn't work properly, the trailer lights and other functions will not be available.

It's impossible to repair this module if it's broken. But I should say that it's rarely broken. Sometimes, it may develop a glitch and it will be cured by just completely resetting the truck. One of the possible ways to do that is to disconnect the battery for 10 minutes.

5. Other minor issue in your truck

Also, I've seen this problem happen when the truck has issues with the brake switch or blinker stalk. When something is wrong with anything that sends the information to the trailer's lighting system, this message may pop up.

Also, I've seen people turning on headlights and everything worked properly. With headlights off, the trailer lights weren't working. When the lights were on again, everything started working properly and the message disappeared. Maybe, you should try this first.

What should you do when you see the trailer lighting problem?

Well, first of all, you should do the following:

• try turning on or off your headlights and see if this solves your problem;
• check if all the light bulbs are OK in your trailer;
• ask someone to check which lights don't work on your trailer;
• pay attention to blinkers and stoplights because they are crucial for safety;
• try disconnecting the trailer and connecting it back;
• look at the connector and see if it's oxidized;
• check the fuses that control the trailer lighting and other trailer-connected things;
• disconnect the battery in your 12V battery for 10 minutes to reset the trailer control module and other modules in your truck.

These are free and simple things you may try doing. At least, you may try all of them before you go to get some professional help and pay some dollars from your pocket. This will help you understand what's happening with your trailer or truck before you take out your wallet.

But if these simple things don't help, I strongly recommend the following:

• go to the dealer and ask if they have a fresh update for the software in your truck;
• the only software that can help is the software for the trailer control module, so no need to pay for an entire update if everything else works fine;
• if this doesn't help, ask them to install the 7-pin connector or have it installed elsewhere;
• if this doesn't help, ask the dealer to diagnose the trailer control module and other possible units that can influence the work of the system.

This will eventually help you solve the problem. There is just nothing else that can potentially cause this problem.

Can you drive with this error message?

If your dash in the Ford truck says "Trailer Light Module Fault", it means that one or several lights on your trailer may not be working right now. If it's daytime and you are driving on the empty highway with just no other cars around, this is considered pretty safe.

But if you are driving in the city and stop lights fail to work on your trailer or there is one blinker that doesn't activate, this may lead to accidents and you will eventually be in charge of them.

It's not uncommon to get a ticket for poorly working trailer lights, so I don't recommend driving with this message on your dash. At least, you need to learn which lights don't work and how you can solve this issue right there and then.

Final thoughts

Be careful and avoid driving with your trailer lights failing to work. This may lead to unpleasant situations on the road and eventually cause serious problems. Naturally, you will want to stop and check which lights fail to work. Also, you may try all the DIY solutions that I listed in this article.

If nothing helps you get your lights back, it's time to go to the dealer or to a very good and trusted repair shop. Be careful when the dealer offers you expensive ways to solve the problem and tell them that you will only pay for this if their work will result in a solution for this problem. Otherwise, you will pay thousands for unnecessary software updates without any good results.