Fixing False Low Air Pressure Alarms in Freightliner Cascadia Truck

Provided by: DIY Semi

If you're driving a Freightliner Cascadia and getting that annoying brake drag warning—even when your air pressure is full—don’t panic. This is a common issue with a surprisingly easy fix. In this guide, we’ll walk you through how to replace the brake drag switch and eliminate the alert for good.

This repair can save you time, money, and a trip to the shop. Whether you're a seasoned driver or just getting started, this is a DIY job you can handle.

What You'll Need

Before you begin, make sure you have the right parts and tools on hand.

Parts:

• Brake Drag Switch
  
  

• Updated Wiring Harness
  Some trucks will require this harness to match the new switch. It bridges the gap between old connectors and the newer version.

Tools:

• T25 Torx Driver
  
  
• 1-1/8” Wrench or deep socket
  
  
• Flashlight or work light
  
  
• Clean rag or shop towel
  
  

Step-by-Step Instructions

1. Remove the Dashboard Trim

Start by removing the dash trim to reach the switch:

• Take out three screws holding the upper panel using a T25 Torx.
  
  
• Remove two additional screws on the center section.
  
  
• Loosen nearby trim slightly to get everything out cleanly.

Keep track of all your screws and store them in a cup or container to avoid losing them.

2. Find the Brake Drag Switch

Once the panel is off, you’ll see a small cluster of sensors behind the dash. The brake drag switch is usually located at the top and may have a blue mark for easy ID.

There’s not a lot of room, so you may need to use an open-end wrench instead of a socket. Carefully unplug the existing wires before unscrewing the switch.

3. Install the New Switch

Take a look at the old and new switches. If the plugs don’t match, use the new wiring harness.

• Thread the new switch in by hand until it’s snug.
  
  
• Give it a gentle turn with your wrench to tighten—don’t overdo it. The threads go into a brass fitting and over-tightening could cause serious damage.
  
  

If you’re not sure, it’s better to under-tighten slightly than risk a cracked fitting.

4. Connect the Wiring

• Connect the old wiring harness to one end of the adapter.
  
  
• Connect the other end to the new sensor.
  
  
• Double-check for dirt, oil, or pet hair near the sensors—these can interfere with performance.
  
  

Yes, dog hair inside dashboards is more common than you think, and it’s a big reason shops charge a cleaning deposit.

5. Reassemble and Test

Once the sensor and harness are installed, reattach the panels and screws.

To test:

• Turn on the ignition.
  
  
• Build full air pressure.
  
  
• Push in the yellow brake button.
  
  

If everything is working, the alarm will stay off. That means your brake drag issue is fixed.

Save Time and Money

By doing this yourself, you’ll avoid:

• At least an hour of labor charges
  
  
• Shop supply and environmental fees
  
  
• Diagnostic and “miscellaneous” shop charges
  
  

This fix can easily save you $200 or more, and now you know how to handle it in the future.

Quick Recap

• Order the correct brake drag switch
  
  
• Install the adapter harness if needed
  
  
• Remove and replace the switch
  
  
• Test for proper function
  
  
• Save time, money, and avoid a shop visit
  
  

Get Everything You Need at FindItParts.com

This repair was made easy with help from Find It Parts, where you’ll find:

• A massive inventory of OEM and aftermarket parts
  
  
• Expert help finding part numbers
  
  

Need replacement seats or accessories? FinditParts offers a wide selection of seats, bolts, and other Freightliner-compatible parts-both OEM and aftermarket. Browse today for competitive pricing and fast shipping.

And don't forget to watch DIYSEMI's video for exclusive discounts on truck parts and tools to make your next DIY project even easier!

Fixing a brake drag warning may seem intimidating at first, but it's an easy win for any DIY truck owner. With the right tools and parts from FinditParts, you can get back on the road safely and confidently—without paying a shop to do what you just did yourself.

Do you buy parts online often? Check out our blog Costly Mistakes to Avoid When Buying Semi Truck Parts. Check out more How-To Guides at FindItParts.com for clear, simple steps anyone can follow.