This article will address the commonly encountered warning alert in Ford vehicles, the “Park Brake Limited Function Service Required.”
I will explain its meaning, primary causes, and how to go about fixing and resetting the message.
Let’s get into it!
Parking Brake System Overview
Before we dive deep into what is causing this warning message,
It’s important to understand what a parking brake is and why it is important on your Ford.
In simple terms, the parking brake is commonly known as a hand brake (on older models). It is a mechanical device that locks the rear wheels of your vehicle, preventing it from rolling when parking.
On newer models, Ford introduced an electric parking brake.
Ford Electric Parking Brake Explained
The Ford electric parking brake replaces the old mechanical parking brake or handbrake. It works by electrically holding the rear brakes when you want to keep the vehicle stationary.
You operate the electric parking brake using a switch in the center console, usually near the gear shifter.
To apply the parking brake, just pull up on the switch. The brake system warning light will flash to let you know it’s set.
To release the parking brake, press the switch down while your foot is on the brake pedal.
Or it will automatically release when you press the accelerator to drive away (as long as the driver’s door is closed).
The electric parking brake has a few advantages over the old handbrake.
It frees up space between the seats by removing the mechanical brake handle. And it can automatically release when you drive off, which makes starting on hills easier.
The downside of this type of parking brake is the fact that it is electronically controlled, and a lot can go wrong compared to the traditional hand brake.
What Does “Park Brake Limited Function Service Required” Mean?
Now that you are up to speed on what a parking brake on your Ford is
Let’s look at what the “park brake limited function service required” message means.
Simply put, This message indicates there is a problem with the electric parking brake system in your Ford vehicle.
The electric parking brake relies on electrical power and the braking system to operate.
If there is an issue detected with the parking brake motors, ABS, or Battery voltage, the system goes into a limited functionality mode (Leading causes below)
When this message appears, it means the parking brake may not be functioning properly.
Park Brake Limited Function Service Required Causes
Since your vehicle uses an electric park brake, technically, a lot cause this alert,
However, based on my experience as a mechanic, I have narrowed it down to the following:
1. Bad Parking Brake Wiring Harness:
The leading cause of the Park brake limited function message is a bad wiring harness.
The parking brake system on your Ford is electric, so any issues with the wire can cause this alert to appear.
When the wire is damaged or corroded due to age, moisture, or other factors,
it won’t be able to send a signal from the Park brake back to your vehicle’s computer for processing.
Fortunately, the wiring harness is relatively inexpensive. You can get both sides for $120-150.
2. Damaged Parking Brake Actuator Switch:
The second common cause of the message is a bad parking brake actuator switch.
The parking brake actuator switch is the button or lever you manually press to turn the parking brake on and off.
This switch can fail internally due to wear, contaminants getting inside, or electrical issues.
For example, the contacts inside the switch can get dirty or burned, preventing them from properly closing the circuit when pressed.
A damaged parking brake switch will not be able to properly send activation signals to the parking brake control module.
3. Faulty Parking Brake Motor:
Ford’s electric parking brake system uses a small electric motor at each rear brake caliper to actuate the parking brake pads.
These motors can fail over time due to normal wear or internal damage.
Issues like burned windings, stripped gears, stuck rotors, or excessive friction will cause the motors not to function properly.
When one or both parking brake motors fail, the system goes into limited functionality. The parking brake may not fully engage or release.
4. Low Battery Voltage:
The fourth reason for the park brake limited function warning is a weak battery.
The electric parking brake motors and control module require a minimum battery voltage (about 12.6 volts) to operate correctly.
Weak battery connections, a failing alternator, a defective battery, or a parasitic electrical drain can cause low system voltage.
If the supply voltage drops too low, the parking brake components may not work normally.
5. Failing ABS Module:
The anti-lock brake system (ABS) module has built-in control logic that operates the electric parking brake function.
If the ABS module is defective, communication errors will occur between it and the parking brake motors.
The ABS module should be scanned for diagnostic trouble codes to identify issues with its internal circuitry.
A faulty ABS module can sometimes be repaired or reprogrammed. Otherwise, it will need replacement.
6. Brake Calipers Going Bad:
The sixth and final leading cause of the “Park brake limited function service required” is damaged brake calipers.
Problems inside the rear brake calipers can prevent the electric parking brake from fully engaging.
Sticky caliper pistons, contaminated friction pads, damaged seals, and caliper springs losing tension can all contribute to parking brake issues.
How to Fix and Reset the Park Brake Limited Function Warning
Now that we discussed the potential causes of this problem let’s now look at the things you can do to fix and reset the alert.
Test and Charge Battery
The first thing that I recommend that you do is to check your battery.
Start with a simple battery test to check for adequate voltage and cold cranking amps.
Recharge or replace the battery if it is weak.
This is an inexpensive first step that can potentially resolve low voltage issues that affect the parking brake.
Check Wiring Harness
Since a damaged park brake wiring harness is the most common cause of this warning,
The next thing you want to look at is the wiring harness.
Visually inspect the parking brake wiring harness and connectors for damage, corrosion, or loose pins. Repair or replace damaged wiring as needed.
Diagnose ABS Module
Have the dealer or repair shop scan the ABS module for trouble codes.
Diagnostic trouble codes can help isolate the root issue. Reprogramming or replacing the ABS module may be required.
Replace Actuator Switch
If determined to be faulty, replace the parking brake actuator switch. This may include recalibrating the new switch if required.
Repair Parking Brake Motors
If one or both parking brake motors are defective, they must be repaired or replaced. This may include adjusting the brake calipers after the new motor installation.
Additional Sources
https://www.fordservicecontent.com/Ford_Content/vdirsnet/OwnerManual/Home/electric-parking-brake
https://www.fordedgeforum.com/topic/28321-parking-brake-limited-function/
https://www.caranddriver.com/news/a44690504/ford-f-150-parking-brake-recall/