Monitor Description

C139A: 

1. After the power switch is turned off, the skid control ECU (brake booster with master cylinder assembly) automatically performs a pressure increase check to detect malfunctions that would be difficult to detect during normal braking.

   During the current trip when the vehicle is being driven at a certain speed or more and the following sequence is met, if the skid control ECU (brake booster with master cylinder assembly) judges that there is a malfunction in a brake line in either of 2 systems, the MIL is illuminated and this DTC is stored.

   1. When the switching solenoid (SSA) and switching solenoid (SGH) are closed and the linear solenoid (SLA) is operating to increase servo pressure, the reaction force pressure rises simultaneously. When there is a malfunction in 1 system, the stroke amount increases because the amount of increase in reaction force pressure is proportional to the output piston stroke amount; therefore, when the reaction force pressure is a specific value or more for a certain amount of time, the system judges that there is a malfunction.

      Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

C139D: 

1. When the brake pedal is depressed, the skid control ECU (brake booster with master cylinder assembly) monitors the servo pressure and increases the servo pressure by driving the linear solenoid (SLA).

   When the brake pedal is depressed, if the actual servo pressure does not change even when the target servo pressure increases for a certain amount of time, the skid control ECU (brake booster with master cylinder assembly) judges that the linear solenoid (SLA) is stuck closed (the pressure increase during initial braking is abnormal) and illuminates the MIL and stores this DTC.

C13CD and C13CE: 

1. The skid control ECU (brake booster with master cylinder assembly) monitors the relationship between the specified increase or decrease in servo pressure and the target brake fluid pressure.

   When the brake pedal is depressed and the relationship between the servo pressure and the target brake fluid pressure is outside of the normal range, the skid control ECU (brake booster with master cylinder assembly) judges that the increasing pressure is abnormal and illuminates the MIL and stores a DTC.

   Furthermore, when the brake pedal is released or while braking is being performed and the relationship between the servo pressure and the target brake fluid pressure is outside of the normal range, the skid control ECU (brake booster with master cylinder assembly) judges that the decreasing pressure is abnormal and illuminates the MIL and stores a DTC.

C1400: 

1. After the power switch is turned off, the skid control ECU (brake booster with master cylinder assembly) automatically performs a pressure increase check to detect malfunctions that would be difficult to detect during normal braking.

   During the current trip when the vehicle is being driven at a certain speed or more and the following sequence is met, the skid control ECU (brake booster with master cylinder assembly) judges that the ABS reduction solenoid valve is leaking and illuminates the MIL and stores this DTC.

   HINT: 

   Although the following sequence is related to the front left and front right, an identical sequence is performed to check for leaks in the rear left and rear right.

   1. The brake fluid pressure at the front left and front right wheel cylinders is equal to that of the brake booster with master cylinder assembly. No brake fluid pressure is applied to the rear wheel cylinders.
   2. The ABS holding solenoid valves of the 4 wheels are closed to isolate the brake booster with master cylinder assembly and each wheel cylinder, and the rear left and rear right ABS reduction solenoids are opened. At this time, the pressure does not change if there is no leak; however, if a front left or front right ABS reduction solenoid valve is leaking, because both wheel cylinders of the system that is leaking (front right and rear left, or front left and rear right) are connected, the pressure of the front wheel cylinder of the leaking system falls lower than that of the brake booster with master cylinder assembly.
   3. When the front right and front left ABS holding solenoid valves are opened, because brake fluid flows from the brake booster with master cylinder assembly to the leaking system, the servo pressure temporarily drops. At this time, if the drop in servo pressure is at a specific value or more and the servo pressure decreases at a specific value or less, it is temporarily judged that there is a leak malfunction.
   4. In the case of (c), if the pressure temporarily drops (temporarily judged as a leak malfunction), the ABS reduction solenoid valves are opened and closed repeatedly to eliminate the leak.

      Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   5. Because the ABS reduction solenoid valve is leaking, brake fluid leaks to the reservoir inside the brake actuator assembly, such as in the case of (a). When the ABS pump motor is operated in this situation, brake fluid in the reservoir is pumped to the brake booster with master cylinder assembly and the servo pressure increases. As the increase in servo pressure loads the ABS pump motor, a rapid voltage drop is produced when the pump motor is stopped. Because of that, if the increase in servo pressure when the ABS pump motor is operating is above a specific value, and the time taken for the ABS pump motor voltage to drop when the ABS pump motor stops operating is shorter than normal, it is judged that there is a malfunction.

      Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

C14EE and C14F7: 

1. After the power switch is turned off, the skid control ECU (brake booster with master cylinder assembly) automatically performs a pressure increase check to detect malfunctions that would be difficult to detect during normal braking.

   During the current trip when the vehicle is being driven at a certain speed or more and the following sequence is met, the skid control ECU (brake booster with master cylinder assembly) judges that the switching solenoid (SSA) or switching solenoid (SGH) is stuck closed and illuminates the MIL and stores a DTC.

   1. When the linear solenoid (SLR) is being operated to reduce servo pressure and the switching solenoid (SSA) and switching solenoid (SGH) are both closed, when the output piston is released, the volume of the reaction chamber expands, and because brake fluid is not introduced, a negative pressure is created.
   2. In the case of (a), if the negative pressure does not change for a certain amount of time, the skid control ECU (brake booster with master cylinder assembly) repeatedly opens and closes the switching solenoid (SSA) and switching solenoid (SGH).
   3. After (b) is performed, the linear solenoid (SLA) is operated to increase servo pressure and the reaction force pressure rises. When the switching solenoid (SSA) is instructed to be off (open) or the switching solenoid (SGH) is instructed to be on (open) and there is a stuck closed malfunction, because the reaction force pressure does not reduce, when the reaction pressure exceeds a specific value for a certain amount of time, the skid control ECU (brake booster with master cylinder assembly) judges that there is a malfunction.

      Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

      Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002