DTC C1256: Accumulator Low Pressure [08/2015 - ]: Procedure

1. Clear the DTCs (Refer to DTC CHECK / CLEAR [08/2015 - 08/2019] , or refer to DTC CHECK / CLEAR [08/2019 - ] ).
2. Turn the ignition switch off.
3. Depress the brake pedal 20 times or more.
4. Turn the ignition switch to ON.
5. Wait for 99 seconds.
6. Check if the same DTC is output (Refer to DTC CHECK / CLEAR [08/2015 - 08/2019] , or refer to DTC CHECK / CLEAR [08/2019 - ] ).
   RESULT
   
   

   Result	Proceed to
   DTC is output	A
   DTC is not output	B

   HINT: 

   Excessive brake pedal operation results in abnormal accumulator pressure consumption. This is normal.

Result: 

B 

USE SIMULATION METHOD TO CHECK 

(Refer to HOW TO PROCEED WITH TROUBLESHOOTING [08/2015 - 08/2019] , or refer to HOW TO PROCEED WITH TROUBLESHOOTING [08/2019 - ] )

Result: 

A 

See step  2

1. Inspect brake booster pump power supply system function.
   1. Turn the ignition switch off.
   2. Depress the brake pedal 20 times or more to release the pressure in the accumulator.

      HINT: 

      When the pressure is released, the brake pedal stroke becomes longer.

   3. Check that the brake fluid level is at the MAX level.
   4. Chock the 4 wheels and release the parking brake.
   5. Turn the ignition switch to ON and measure the brake booster pump operating time (the time from when the brake booster pump starts operating until it stops).

      OK

      20 to 80 seconds

   6. Start the engine after the brake boost pump stops.
   7. Check that the ABS warning light and slip indicator light are not illuminated.
   8. Turn off the engine, and then turn the ignition switch to ON.
   9. Check that the brake boost pump operates and then stops when the brake pedal is depressed 4 or 5 times.
   10. Depress the brake pedal 4 or 5 times and measure the brake booster pump operating time (the time from when the brake booster pump starts operating until it stops).

       OK

       2 to 11 seconds

   11. Check that the brake warning light illuminates and the buzzer sounds when the brake pedal is fully depressed continuously 15 to 20 times.
       NOTE:

       Wait 120 seconds or more after turning the ignition switch to ON before performing this inspection.

2. Check brake booster operation.
   1. Turn the ignition switch off.
   2. Depress the brake pedal 20 times or more to release the pressure in the accumulator.

      HINT: 

      When the pressure is released, the brake pedal stroke becomes longer.

   3. Depress the brake pedal, start the engine, and check the change in the brake pedal height.

      OK

      The brake pedal moves slightly inward.

3. Inspect brake master cylinder fluid pressure change (Refer to PROCEDURE - Step 1 ).

Result: 

NG 

See step  5

Result: 

OK 

See step  3

1. Turn the ignition switch off.
2. Connect the Techstream to the DLC3.
3. Turn the ignition switch to ON.
4. Turn the Techstream on.
5. Enter the following menus: Chassis / ABS/VSC/TRAC / Data List.
   ABS/VSC/TRAC
   
   

   Tester Display	Measurement Item/Range	Normal Condition	Diagnostic Note
   Accumulator Sensor	Accumulator pressure sensor reading/ Min.: 0.00 V, Max.: 5.00 V	3.58 to 5 V	If the value is constant regardless of the pump operation, an accumulator pressure sensor malfunction is suspected.

6. Check that the accumulator output value is normal.

   OK

   Accumulator pressure sensor value is normal.

Result: 

NG 

REPLACE MASTER CYLINDER SOLENOID 

(Refer to DISASSEMBLY [08/2015 - ] )

Result: 

OK 

See step  4

1. Clear the DTCs (Refer to DTC CHECK / CLEAR [08/2015 - 08/2019] , or refer to DTC CHECK / CLEAR [08/2019 - ] ).
2. Turn the ignition switch off.
3. Check if the same DTC is output (Refer to DTC CHECK / CLEAR [08/2015 - 08/2019] , or refer to DTC CHECK / CLEAR [08/2019 - ] ).
   RESULT
   
   

   Result	Proceed to
   DTC is output	A
   DTC is not output	B

Result: 

A 

REPLACE MASTER CYLINDER SOLENOID 

(Refer to DISASSEMBLY [08/2015 - ] )

Result: 

B 

USE SIMULATION METHOD TO CHECK 

(Refer to HOW TO PROCEED WITH TROUBLESHOOTING [08/2015 - 08/2019] , or refer to HOW TO PROCEED WITH TROUBLESHOOTING [08/2019 - ] )

1. Remove the hydraulic brake booster assembly (Refer to REMOVAL [08/2015 - ] ).
2. Using a screwdriver, remove the 2 screws and pull out the wire harness from the master cylinder solenoid.
3. Measure the resistance according to the value(s) in the table below.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   Red wire terminal - Black wire terminal	Always	Below 2 Ω

   TEXT IN ILLUSTRATION
   
   

   *1	Pump motor wire harness
   *a	Red wire
   *b	Black wire

4. Install the pump motor wire harness to the master cylinder solenoid with the 2 screws.

   Torque: 2.9 N*m (30 kgf*cm, 26 in.*lbf) 

Result: 

OK 

REPLACE HYDRAULIC BRAKE BOOSTER ASSEMBLY 

(Refer to REMOVAL [08/2015 - ] )

Result: 

NG 

REPLACE BRAKE BOOSTER WITH ACCUMULATOR PUMP ASSEMBLY 

(Refer to DISASSEMBLY [08/2015 - ] )