DTC C1256/56: Accumulator Low Pressure [10/2014 - ]: Procedure

1. Ask the customer if frequent braking was performed while the brake warning light / yellow (minor malfunction) was on.

   OK

   Result	Proceed to
   Frequent braking was not performed.	A
   Frequent braking was performed.	B

   HINT: 

   This DTC may be stored even if the accumulator pressure drops only temporarily due to frequent braking.

Result: 

B 

END 

Result: 

A 

See step  2

1. Make sure that there is no looseness at the locking part and the connecting part of the connectors.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

2. Disconnect the A56 and A57 brake booster pump assembly connectors.
3. Measure the resistance according to the value (s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   A56-2 (BM1) - A56-4 (GND1)	Always	Below 10 Ω
   A57-2 (BM2) - A57-1 (GND2)	Always	Below 10 Ω
   A56-2 (BM1) - A57-2 (BM2)	Always	Below 1 Ω
   A56-4 (GND1) - A57-1 (GND2)	Always	Below 1 Ω

   TEXT IN ILLUSTRATION
   
   

   *a	Component without harness connected (Brake Booster Pump Assembly)

Result: 

NG 

REPLACE BRAKE BOOSTER PUMP ASSEMBLY 

(Refer to REMOVAL [10/2014 - ] )

Result: 

OK 

See step  3

1. Reconnect the A56 and A57 brake booster pump assembly connectors.
2. Connect the Techstream to the DLC3.
3. Turn the power switch on (IG).
4. Select the Data List on the Techstream (Refer to DATA LIST / ACTIVE TEST [10/2014 - 10/2015] or DATA LIST / ACTIVE TEST [10/2015 - ] ).
   ABS/VSC/TRAC
   
   

   Tester Display	Measurement Item/Range	Normal Condition	Diagnostic Note
   Accumulator Sensor	Accumulator pressure sensor / Min.: 0.00 V, Max.: 5.00 V	Specified value: 2.90 to 4.20 V	When brake fluid is stored in the accumulator: Accumulator pressure changes in accordance with volume of fluid stored in the accumulator

5. Wait for 30 seconds without depressing the brake pedal.
6. Check that the accumulator pressure sensor output value change is within the specified range.

   OK

   Accumulator pressure sensor output value change is less than 0.55 V.

Result: 

OK 

USE SIMULATION METHOD TO CHECK 

(Refer to HOW TO PROCEED WITH TROUBLESHOOTING [10/2014 - 10/2015] or HOW TO PROCEED WITH TROUBLESHOOTING [10/2015 - ] )

Result: 

NG 

See step  4

1. Select the Active Test on the Techstream (Refer to DATA LIST / ACTIVE TEST [10/2014 - 10/2015] or DATA LIST / ACTIVE TEST [10/2015 - ] ).

   HINT: 

   The Active Test can be performed when the following conditions are met.

   • ABS main relay is on.
   • Shift lever is in P.
   • Parking brake is applied.
   • Vehicle speed is 0 km/h (0 mph).
   ABS/VSC/TRAC
   
   

   Tester Display	Test Part	Control Range	Diagnostic Note
   ECB* Solenoid (SMC/SRC/SCC)	Switching solenoid valve (SMC/SRC/SCC)	Solenoid ON/OFF	Operation sound of solenoid (clicking sound) can be heard

   *: Electronically Controlled Brake System

2. Perform the Active Test of the solenoid using the Techstream.
3. Select the Data List on the Techstream (Refer to DATA LIST / ACTIVE TEST [10/2014 - 10/2015] or DATA LIST / ACTIVE TEST [10/2015 - ] ).
   ABS/VSC/TRAC
   
   

   Tester Display	Measurement Item/Range	Normal Condition	Diagnostic Note
   Wheel Cylinder Pressure Sensor	Wheel cylinder pressure sensor / Min.: 0.00 V, Max.: 5.00 V	Brake pedal released: 0.10 to 0.90 V	Reading increases when brake pedal is depressed

4. Check that the output value of the wheel cylinder pressure sensor does not increase.

   OK

   The output value of the wheel cylinder pressure sensor does not increase.

   HINT: 

   If the output value increases, there may be brake fluid leaks in the brake actuator.

Result: 

OK 

REPLACE BRAKE BOOSTER PUMP ASSEMBLY 

(Refer to REMOVAL [10/2014 - ] )

Result: 

NG 

REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY 

(Refer to REMOVAL [10/2014 - ] )