Inspection Procedure

HINT:

When C1202/68, C1241/41, C1252/52, C1253/53 or C1391/69 are output together with C1256/57, inspect and repair the trouble areas indicated by C1202/68, C1241/41, C1252/52, C1253/53 or C1391/69 first.

1. INSPECT BRAKE ACCUMULATOR PUMP 
   Fig 1: Identifying A23 And A24 Accumulator Connectors
   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   1. Disconnect the A23 and A24 accumulator connectors.
   2. Measure the resistance according to the value (s) in the table below.

      Standard resistance 

      TESTER CONNECTION SPECIFIED CONDITION
      
      

      Tester Connection	Condition	Specified Condition
      A2 (BM1)-A4 (GND1)	Always	10 kΩ or higher
      B2 (BM2)-A4 (GND1)
      A2 (BM1)-B2 (BM2)	Always	Below 1 Ω
      A4 (GND1)-B1 (GND2)
      A2 (BM1)-A1 (MTT)	Always	950 to 1050 Ω
      B2 (BM2) - A1 (MTT)

   NG: REPLACE BRAKE ACCUMULATOR PUMP (See  REMOVAL   ) 

   OK: GO TO NEXT STEP 

2. READ VALUE OF INTELLIGENT TESTER OR TECHSTREAM (ACCUMULATOR PRESSURE SENSOR) 
   1. Connect the intelligent tester or Techstream to the DLC3.
   2. Turn the engine switch on (IG).
   3. Select the DATA LIST mode on the intelligent tester or Techstream.
      1. Intelligent tester

         Skid control ECU: 

         SKID CONTROL ECU
         
         

         Tester Display	Measurement Item/Range	Normal Condition	Diagnostic Note
         ACC PRESS SENS	Accumulator pressure sensor / min.: 0 V, max.: 5 V	Specified value: 2.6 to 3.8 V	-

      2. Techstream

         Skid control ECU: 

         SKID CONTROL ECU
         
         

         Tester Display	Measurement Item/Range	Normal Condition	Diagnostic Note
         Accumulator Sensor	Accumulator pressure sensor / min.: 0 V, max.: 5 V	Specified value: 2.6 to 3.8 V	-

   4. Depress the brake pedal 4 or 5 times to operate the pump motor, and check the output value on the intelligent tester with the motor stopped (not braking) for 30 seconds.

      OK: The accumulator pressure sensor voltage change is within 0.2 V. 

   NG: Go to step   4 

   OK: GO TO NEXT STEP 

3. RECONFIRM DTC 
   1. Clear the DTC (see DTC CHECK/CLEAR  ).
   2. Turn the engine switch on (IG).
   3. Check if the same DTC is recorded (see DTC CHECK/CLEAR  ).

      HINT:

      Reinstall the sensors, connectors, etc. and restore the vehicle to its prior condition before rechecking for DTCs.

      Result 

      RESULT REFERENCE
      
      

      Condition	Proceed to
      DTC (C1256/57) is not output	A
      DTC (C1256/57) is output	B

   B: REPLACE SKID CONTROL ECU (See  REMOVAL   ) 

   A: GO TO NEXT STEP 

   END 

4. PERFORM ACTIVE TEST BY INTELLIGENT TESTER (ELECTRONICALLY CONTROLLED BRAKE SYSTEM SOLENOID) 
   1. Move the shift lever to the P position.
   2. Apply the parking brake.
   3. Connect the intelligent tester or Techstream to the DLC3.
   4. Turn the engine switch on (IG).
   5. Select the ACTIVE TEST mode on the intelligent tester or Techstream.
      1. Intelligent tester

         Skid control ECU 

         SKID CONTROL ECU
         
         

         Tester Display	Test Part	Control Range	Diagnostic Note
         SMC1	Turns electronically controlled brake system solenoid (SMC1)	ON / OFF	Operation sound of solenoid (clicking sound) can be heard
         SMC2	Turns electronically controlled brake system solenoid (SMC2)	ON / OFF	Operation sound of solenoid (clicking sound) can be heard

      2. Techstream

         Skid control ECU 

         SKID CONTROL ECU
         
         

         Tester Display	Test Part	Control Range	Diagnostic Note
         Electronically Controlled Brake System Solenoid (SMC1)	Turns electronically controlled brake system solenoid (SMC1)	ON/OFF	Operation sound of solenoid (clicking sound) can be heard
         Electronically Controlled Brake System Solenoid (SMC2)	Turns electronically controlled brake system solenoid (SMC2)	ON / OFF	Operation sound of solenoid (clicking sound) can be heard

   6. Using the intelligent tester, turn SMC1 and SMC2 ON.
      Fig 2: Brake Actuator Inner Diagram

      Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   7. Check that each wheel cylinder's output value increases.

      OK: Each wheel cylinder's output value increases. 

      HINT:

      If each wheel cylinder's output value does not increase, there may be a brake fluid leak in the brake actuator.

   NG: REPLACE BRAKE ACTUATOR (See  REMOVAL   ) 

   OK: REPLACE BRAKE ACCUMULATOR PUMP (See  REMOVAL   )