Toyota Pre-Collision System Malfunction Warning Meaning & Causes

Many newer Toyota vehicles have a Pre-Collision System (PCS) that uses a radar sensor and front camera to detect objects in front of the car in the direction of travel, such as vehicles, pedestrians, and bicycles, and determine if there is a risk of a frontal collision with a similar object. In this case, PCS will cause a warning to prompt the driver to take evasive action and increase the brake pressure to assist the driver in avoiding the collision. If the PCS senses that the risk of collision is very high, it can automatically apply the brakes to avoid a collision or reduce the impact of a crash. PCS can be turned on and off, and the timing of the warning can be adjusted. Suppose your Toyota vehicle is malfunctioning in the Pre-Collision System (PCS). In that case, the car may not be able to detect an imminent collision or perform any action to assist you in avoiding or reducing the impact of a crash. A possible cause of a PCS malfunction can be a problem in the radar or camera sensors, a software or programming issue, or a situation in PCS hardware components.

Although it would not be advisable to drive with a malfunctioning pre-collision system, we recommend that you, at minimum, inspect key vehicle elements visually to ensure they are intact, not damaged, or covered with dirt. As soon as you identify that your PCS is malfunctioning, you must diagnose and repair it as quickly as possible because driving with a malfunctioning PCS can expose you to a potential collision. Use the YOUCANIC whole system scanner for a system-wide scan, and refer to any fault codes that read ACTIVE or PRESENT.

If the Pre-Collision System determines a risk of a frontal collision, the buzzer sounds and the warning message ‘BRAKE’ or ‘BRAKE NOW’ are displayed on the multi-information display. It is your responsibility to take evasive action to help avoid a collision.’ Toyota’s PCS is a type of vehicle safety feature designed to reduce the collision impact or prevent a collision by warning or aiding the driver in avoiding a collision with another car or person who may be in the vehicle’s path. It employs the functions of radar and a camera to detect that the vehicle it is installed is about to collide with another object, such as another car or a pedestrian.

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

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 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; 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.

Common causes for Toyota’s Pre-collision System malfunction

If the PCS is malfunctioning, the PCS warning light will illuminate, and the multi-information display will display ‘VSC Turned OFF Pre-Collision Brake System Unavailable.’

• 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
• The charging system fault blown the fuse of the 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 during an accident or if it is 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, the radar’s front side may become coated with contaminants, which offset its readings. These include 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 as an obstruction.

Aftermarket grilles

• Aftermarket grilles were a widespread alteration, particularly for the late Tacoma, and those who had installed new products into the pickup’s front end were also reporting issues with the Pre-collision System remaining un-deployed until the very last second, if at all. This condition arose when the new product did not include mounting points for the radar, but it mostly happened when the sensor’s orientation wasn’t the same as it had been in the original grille. The explanation is simple: when the sensor is misaligned, it can no longer take proper readings from its surroundings, and its inability to do so will confound the ECU that controls the Pre-collision system. Of course, the sensor could be recalibrated, and some owners visited their Toyota dealer and found that the system was operating correctly. In many other cases, the owners discovered that the problem arose because the mounting points on the front of the vehicle that supported the sensor array hadn’t been appropriately fitted with washers. The most straightforward remedy (which worked and served to improve the mounting points so that all the sensors were better supported in suspension) was to install two washers on both sides of the bracket.

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 determine whether the driver is pressing the brake pedal. Over time, internal wear may cause this sensor to malfunction. The system will malfunction without a signal about whether the brakes are pressed. The brake switch sensor is an inexpensive part that is also easy to replace.

Aftermarket brake controllers

• Some owners equip their Toyota with an aftermarket brake controller, activating the trailer brakes. 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

• A March 2019 recall issued by Toyota Motor Corporation affected some 18-19 Tacoma and Tundra trucks. The problem was caused by moisture getting inside incorrectly installed radar sensors. As part of the remedy program, a Toyota dealership would inspect the vehicle 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. Rodents interfere with the radar’s signal and may even interrupt it. 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, such as 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, 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. Scroll through menus using the LEFT or RIGHT button 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 cannot turn the pre-collision system on and off. Instead, use the YOUCANIC scanner to run a full system scan and determine 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

Conclusion

The Pre-collision system is a safety feature in modern Toyota vehicles that monitors 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 – cartipsdaily.com
2. Toyota Pre Collision System Malfunction Reset: the Easiest Method – Madisonrising.com
3. Pre-Collision System (PCS) warning light – hybridbatteryrepairtoyota.com
4. HOW DOES THE TOYOTA PRE-COLLISION SYSTEM WORK? –  mossytoyota.com
5. TSS/Pre Collision System Malfunction – Forum – tundras.com

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