“EPB Activation Stopped Incompletely” in Lexus RX – What Does It Mean?

The EPB (Electronic Parking Brakes) button made things easier. You only need a single button push to command the motor to lock or release the rear brakes. It takes up a smaller space on your console when put side to side with the traditional handbrake system. Also, it automatically disengages without a lift or a shove.

EPB activation stopped incompletely message highlights

• Common reasons:EPB switch problems, EPB control module glitch, EPB motor problems
• How to fix:play the EPB switch, disconnect the battery for some time
• Possible consequences:EPB may not engage or disengage
• Priority level:High
• Can you drive?Yes
• DIY repair:Impossible
• Repair price range:$150-$950

Electronic Parking Brake Overview

Technology brings convenience close. Most car owners will always pick convenience over other features. 

That's why auto manufacturers introduced the electric parking brake. The braking system is safer, more capable, and more convenient than the traditional handbrake. It's also more accurate than the handbrake system due to its automated operations.

The parking brakes or EPB securely hold the car when you engage the parking gears (P) or when the vehicle detects that it's driving through a steep incline. The brakes work by controlling the rear brakes. A press of the EPB button signals the ECU (Electronic Control Unit) to activate the "locking effect" on the rear brakes and wheels.

A set of electronically controlled motors and a clamping force emerging from the actuator will tighten the wires. Therefore, locking the rear brakes and wheels. The EPB on your Lexus RX will engage the parking gears to prevent backward motion while driving through a steep incline. The "hill-hold" function will prevent your vehicle from rolling down the hill. It also gives you more control as you maneuver a steep descent.

Your parking brakes also act as emergency brakes. It will put your car on auto-hold, supposing an emergency occurs.

It's a vital component. Therefore, don't ignore the display on your multi-information display or resort to a DIY fix.  

"EPB Activation Stopped Incompletely" on Lexus RX

The "EPB Activation Stopped Incompletely" may appear on your Lexus RX's multi-information display when the parking brake develops a fault. Turn the parking brake switch on and off multiple times while checking the multi-information display.

The warning should disappear after several turns. 

 If it doesn't, it means the EPB has developed an activation fault. You may also notice an odd noise each time you try to engage and deactivate the parking brakes. Don't ignore the warning. Take your automobile to the dealer for further assessment. 

What Causes the "EPB Activation Stopped Incompletely" on Lexus RX?

The push-button braking system is an electronically operated component in your car. Hence, it's prone to electronically related faults. Most of these faults may affect wires and switches. The EPB is also prone to non-electronically issues. Here are the common reasons why the "EPB Activation Stopped Incompletely" popped up on your multi-information display. 

• Low Voltage 

Your car's EPB will need electric power to engage or disengage. It's an electronically operated system. Therefore, a low voltage will trigger an EPB warning on your display. 

You'll need to verify your car's voltage before accusing it of triggering the EPB warning on your multi-information display.   

Here's how to examine your car's voltage level:

• Bring your car to a stop.
• Switch off the ignition. Ensure to turn off the headlights before testing the battery.
• Set up your multimeter.
• Connect the probes to the battery terminals. (Red connects to the positive terminal, while black is to the negative terminal). Begin with the red, followed by the black probe.Note:You'll need to interchange the probes if you see a negative reading.
• Read the voltage while the engine is off. Ideally, you should see 12.4V to 12.9V when it is off. Anything less than that means you're dealing with low voltage. Recharge it if the gauge goes below 12.2V.
• Crank your engine. Ask a friend to do it. You can also use a remote starter if you have one. Record the readings. You may notice a quick drop in your voltage. But the gauge shouldn't fall below 9.6V. A lower voltage is an indication that the battery lacks sufficient turnover strength.
• Don't turn off the engine. Let it idle for a short period. You can also engage the park brakes and read the voltage while the engine is on. The alternator will charge your battery. You may see a figure between 13.7V to 14.7V on the multimeter.

A dead module, broken actuators, damaged cables, or a weakened battery cause a low power supply within the EPB system.  

• Corroded Braking Cables

The EPB system will need cables to engage or disengage. They should be operable for the EPB to function as expected. However, they may age as your car ages. 

Therefore, you'll need to assess the cables' condition if the battery supplies enough power to your car's components. Look for exposed parts, cuts, or any signs of deterioration. Check whether the cables running through the switches, actuators, or the module are damaged, open, or shortened. Also, when the EPB cables acquire high resistance, they cause issues within the EPB system. Hence, activating the "EPB Activation Stopped Incompletely" message on the multi-information display. 

• Blown Fuse  

Your car's EPB system needs sufficient voltage for the entire system to function as expected. However, there are instances when the car's power system delivers more current than required. The EPB's fuse will sieve the excess current to protect all the electrical components within your EPB. 

So, you endanger the entire EPB system when you have a shuttered fuse. The openness will limit its ability to control the current flowing through the EPB. Therefore, check the EPB fuse. 

It's easy to assess the fuse. You can do it visually. 

Pull the fuse and assess the element. Check whether there are any signs of wear on the terminals. You'll need to reset the fuse if it's blown.   

• A faulty Brake Switch 

The brake switch sends commands to the ECU and other controllers to activate or disengage the parking brakes. The control module will decipher the command and send a signal to the control motor to initiate the braking process. Therefore, you'll also need to check the switch if you continuously see the "EPB Activation Stopped Incompletely" warning.

A bad switch impacts the brake lights, torque converter control systems within the EPB, and the shift interlock. Apart from the "EPB Activation Stopped Incompletely" you may notice that the parking brakes may fail to release or engage if you have a damaged brake switch. 

You'll need a scanning tool to examine the EPB switch and get live voltage. The scan tool shows you what other controllers within the EPB system see. Connect the scan tool to the switch and check the voltage reading. Visually scan it for any damage or wear. It is prone to dust collection or moisture retention. Therefore, it may suffer physical damage.  

• Miscommunication Between the ECU and the EPB

Your car's EPB connects to the ECU. The actuator will work jointly with the ECU to generate the clamping force the EPB will need to hold the vehicle once you activate the parking gears.   

Therefore, inconsistencies between the ECU and the EPB may trigger the "EPB Activation Stopped Incompletely" warning. You'll need to evaluate if there is a fault with the ECU or the actuator. 

Examine if your vehicle has a broken actuator. You can do it visually. A broken actuator can cause miscommunication between the EPB system and the ECU. If you don't observe any issues, use a scan tool. Using the tool will let you see the errors the control module sees. 

You'll have to check the ECU's condition if the actuator has no damage. 

Check the ECU's voltage because a low voltage can cause data inconsistency. Reset the multimeter and connect the red terminal with the wire you'd wish to test. Let the black end connect to the ground. It's advisable to test every component on the ECU. Therefore, test the fuse, relay, and wires running through the ECU.

An OBD-II scanner will pinpoint the exact issues through error codes. Also, use the scan tool to examine the control module. The ECU must communicate continuously with the control module for a proper braking process. Therefore, you may experience EPB activation issues if the ECU fails to communicate with the control module.  

Final Thoughts

Different EPB-related issues often trigger the "EPB Activation Stopped Incompletely" on your display. Don't ignore the warning because you may end up jamming or locking the parking brakes. Besides, the electronic parking brake is a vital component of your Lexus RX.  

Therefore, take your Lexus RX to a trusted dealer or mechanic before replacing or fixing anything on the EPB system. We recommend a thorough assessment before fixing any EPB-related issues. Consider getting a full EPB diagnostic.

But in most cases, the solution to the "EPB Activation Stopped Incompletely" troubles will largely depend on the damaged component within the EPB system. The diagnostic will save your pockets hundreds of dollars you might have spent fixing an unrelated issue.