Toyota Pre-Collision System Malfunction Meaning, Causes

Toyota Pre-Collision System Malfunction Meaning, Causes

Pre-collision System will alert the driver with audio and warning red lights if it detects the vehicle is about to collide with an object. If the driver fails to react, the system will apply the brakes and try to stop the vehicle to avoid an accident. Your Toyota or Lexus will likely remain drivable even if a pre-collision system malfunction occurs on the instrument cluster.

While it is not recommended to drive with the pre-collision system malfunctioning, at minimum, you should visually inspect all vehicle conditions to ensure the vehicle will be safe to operate. If you suspect your PCS is malfunctioning, diagnosing and repairing the issue as soon as possible is essential. Continuing to drive with a malfunctioning PCS can leave you at a higher risk of being involved in a collision, so it is important to address the issue as soon as possible. Use the YOUCANIC full system scanner to run a full vehicle scan and pay attention to fault codes that show ACTIVE status.

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“If the Pre-Collision System determines that there is a high risk of a frontal collision, it will sound a buzzer and display a warning message on the multi-information display, encouraging the driver to take action to avoid the collision.” Toyota’s Pre-Collision System (PCS) is a safety feature that is designed to help reduce the severity of a collision or potentially even help the driver avoid a collision altogether. It uses a combination of radar and camera technology to detect when the vehicle is at risk of colliding with another object in its paths, such as another car or pedestrian. When the system detects a potential collision, it can alert the driver and automatically apply the brakes to help reduce the impact—the specific details of how the system works can vary depending on the Toyota model’s specific features.

What does pre-collision system malfunction mean on a Toyota?

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If you ignore this warning, an avoidable accident may not be avoided. The pre-collision dashboard warning light and message will flash for different reasons, including the system not working even temporarily or if the Pre-Collision System has been disabled. As obvious as it may sound, this feature’s failure will impact the vehicle’s overall safety. Pre-collision system malfunction and issues may also affect the operation of cruise control or lane departure assist features. Toyota’s Pre-collision System is a complex system that relies on forward-facing radar and a camera sensor for its operation; fixing it is not always a simple task. The following video shows how to run a full system scan on a Toyota vehicle using the YOUCANIC scanner

On Toyota vehicles, the Pre-Collision System (PCS) utilizes a radar sensor and front camera to identify objects in front of the vehicle, such as vehicles, pedestrians, and bicycles. PCS determines if there is a significant likelihood of a frontal collision with an object. In that case, it will trigger a warning to encourage the driver to take evasive action and increase the potential brake pressure to assist the driver in avoiding the collision. If the PCS determines that the risk of a collision is extremely high, in that case, it will automatically apply the brakes to avoid the collision either or reduce its impact. The PCS can be enabled or disabled, and the warning timing can be modified. If Pre-Collision System (PCS) in your Toyota vehicle is malfunctioning, the vehicle may not be able to detect a potential collision or take appropriate action to help prevent or mitigate the impact of a collision. There are several potential causes for a PCS malfunction, such as a problem with the radar or camera sensors, an issue with the system’s software or programming, or a problem with the system’s hardware components.

Common causes for Toyota’s Pre-collision System malfunction

Front Radar Sensor Distronic

“If the Pre-Collision System (PCS) is not functioning properly, the PCS warning light will turn on, and the message “VSC Turned OFF Pre-Collision Brake System Unavailable” will be displayed on the multi-information display.

  • Dirt and debris on the radar sensor and radar sensor cover
  • VSC (Vehicle Stability Control) system is disabled by the driver or has malfunctioned
  • Defective ABS wheel speed sensor
  • Front camera malfunction radar sensor not working properly
  • Low battery voltage
  • Charging system fault Blown fuse Defective ABS pump.

Broken forward-facing radar

  • The Pre-collision System relies on a forward-facing laser radar, which sits behind the radiator grille. Because of its exposed position, this radar sensor is vulnerable to mechanical damage. This happens either during an accident or if it gets hit by road debris. In addition, constant exposure to harsh weather and moisture doesn’t favor it either. This can lead to a sensor failure; the Pre-collision system light will be on.

Dirty forward-facing radar sensor

  • While driving, radars’ front side may get coated with all sorts of contaminants, which offsets its readings. This includes anything from mud and snow to leaves and dead insects. In most cases, a thorough cleaning will solve the problem. The warning light may also appear during heavy downpours, as the wall of rain acts an obstruction.

Aftermarket grilles

  • Aftermarket grilles, a popular modification, can cause interference with the Pre-collision System even if the new product has mounting points for the radar. In most cases, this happens if the sensor’s position on the aftermarket front grille differs from the original one. The consequent radar misalignment will cause incorrect readings and confuse the Pre-collision system. Although recalibrating the sensor should be possible, visiting a Toyota dealer will usually yield no results. Instead, many Tacoma and Tundra owners found that installing a couple of washers solves the problem.

Lift kits

  • Similar misalignment may occur on some Toyota trucks with lift kits and oversized wheels. An increased distance from the road causes the radar not to adequately see the area in front of it, which offsets the Pre-collision system. Again, the solution to the problem is to realign the radar using several washers. This video explains in detail how to perform this modification.

Faulty brake switch

  • The PCS system uses a signal from the brake sensor to see if the driver is pressing the brake pedal. With time, internal wear may cause this sensor to malfunction. Without the signal about the brakes being pressed or not, the system will malfunction. The brake switch sensor is an inexpensive part, and it is also easy to replace.

Aftermarket brake controllers

  • Some owners equip their Toyota with an aftermarket brake controller, which is used to activate the brakes on the trailer. As it taps into the vehicle’s electrical wiring, this electronic device may interfere with the operation of the Pre-collision system. The solution to the problem is the addition of an extra relay, which triggers the controller only when braking.

Radar sensor recall

  • Some 18-19 Tacoma and Tundra trucks have been affected by a recall issued by Toyota Motor Corporation in March 2019. The problem here was caused by moisture getting inside incorrectly installed radar sensors. As a part of the remedy program, a Toyota dealership would have the vehicle inspected and, if needed, replace the laser sensor.

Damaged wiring and blow fuses

  • Some Toyota models will likely suffer from damaged wiring connecting the radar to the car’s harness. Apart from being mechanically damaged, this issue can also be caused by rodents. This interferes with its signal and may even interrupt it whatsoever. Damaged wiring and consequent electrical shorts can also cause blown fuses.

How to deactivate the Toyota Pre-Collision System?

There are situations where the Pre-Collision System will not work as it should, which is when you want to turn its warning lights off. One of the most common scenarios happens when driving for a long time through a blizzard.

As the falling snow covers the radar, it offsets its readings, consequently causing Pre-Collision System malfunction. A similar will happen during offroad driving, as this safety system sees tall grass as an obstacle.

To turn off the Pre-Collision System, you will need to do the following:

  1. Locate the Meter Control Switch on the steering wheel
  2. Press the UP or DOWN button until the Settings menu appears on the central multi-information display
  3. Using the LEFT or RIGHT button, scroll through menus and find the Pre-Collision System feature
  4. Hold the OK button for 2 seconds to enter the system settings menu
  5. Inside the settings menu, press the OK button once more to deactivate the Pre-Collision System.

If there is a problem with the vehicle, you will not be able to turn on and off the pre-collision system. Instead, use the YOUCANIC scanner to run a full system scan and find out what is wrong. Toyota pre-collision system warning typically comes on along with many other systems that are disabled at the same time:

  • PCS (Pre-Collision system)
  • LTA (Lane Tracing Assist)
  • Automatic High Beam
  • RSA (Road Sign Assist) (if equipped)
  • Dynamic radar cruise control with full-speed range

Frequently Asked Questions

Can I drive my Toyota with the Pre-collision system unavailable?

Unlike things like the check engine light, issues with the Pre-collision system will not affect your Toyota’s driveability. This safety feature only kicks in when the driver is not fully alert. Still, PCS issues can also affect cruise control and other special features. So, if driving a car with a malfunctioning Pre-collision system, you should consider these limitations. Although you don’t have to visit your Toyota dealer immediately because of this, have the PCS system fixed as soon as possible.

Which sensors does the Toyota Pre-collision system use?

The Toyota Pre-collision system uses two separate sensors to gain information about conditions in front of the vehicles. The first is the laser radar, which sits behind the radiator grille and scans the road ahead. There is also a front camera sensor located on the internal mirror.


The Pre-collision system is a safety feature in modern Toyota vehicles that monitor the road ahead for potential obstacles. If it spots anything, this safety system will alert the driver with an appropriate warning message and, if needed, apply the brakes.

Typical issues that cause this system to malfunction include a faulty or misaligned laser sensor and a malfunctioning brake switch. In addition, aftermarket trailer brake controllers can interfere with the operation of the Pre-collision system. To find out, diagnose the vehicle using a YOUCANIC full system scanner.

Additional Resources

  1. How to Fix (Reset) Toyota Pre-Collision System (PCS) Malfunction –
  2. Toyota Pre Collision System Malfunction Reset: the Easiest Method –
  3. Pre-Collision System (PCS) warning light –
  5. TSS/Pre Collision System Malfunction – Forum –

We hope you find the Toyota Pre-Collision System Malfunction Meaning, Causes guide helpful. Check these troubleshooting and repair guides for more help on your Toyota.


  • Rushit Hila • ASE Certified

    Rushit Hila, an ASE-certified engineer (G1 Automotive Maintenance and Repair), brings over two decades of hands-on experience in the automotive world to his writing. With a strong educational background, including a Master of Science in Engineering and a Bachelor of Science in Engineering, he has honed his skills and expertise through years of practical work. As a respected authority in the field, Mr. Hila is dedicated to offering insightful and valuable content that resonates with both vehicle owners and mechanics.

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  1. angel alvarado says:

    how to diagnostic if goog or bad pre collision sensor in toyota corrolla 2019 tanks you

    1. You can use the YOUCANIC scanner to run a health check. If there is any faulty sensor it will show as current fault codes.