DESCRIPTION
INSPECTION PROCEDURE
RECONFIRM DTC
INSPECT HYDRAULIC BRAKE BOOSTER ASSEMBLY FUNCTION
READ VALUE USING GTS (ACCUMULATOR SENSOR)
RECONFIRM DTC
INSPECT BRAKE BOOSTER PUMP ASSEMBLY
DTC C1256 Accumulator Low Pressure
DESCRIPTION
Refer to DTC C1254 ().
| DTC Code | DTC Detection Condition | Trouble Area |
| C1256 | The fluid pressure inside the accumulator is below the standard value. | Brake booster with accumulator pump assembly
Master cylinder solenoid (Accumulator pressure sensor)
Hydraulic brake booster assembly
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INSPECTION PROCEDURE
- After replacing the master cylinder solenoid, perform zero point calibration and store the system information ().
- When DTC C1251, C1253 or C1254 is output together with DTC C1256 inspect and repair the trouble area indicated by DTC C1251, C1253 or C1254 first.
Turn the ignition switch off.
Depress the brake pedal 20 times or more.
Turn the ignition switch to ON.
Check if the same DTC is output ().
Result| Result | Proceed to |
| DTC is output | A |
| DTC is not output | B |
- Excessive brake pedal operation results in abnormal accumulator pressure consumption. This is normal.
| | CHECK FOR INTERMITTENT PROBLEMS ()
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| 2.INSPECT HYDRAULIC BRAKE BOOSTER ASSEMBLY FUNCTION |
Inspect brake booster pump power supply system function.
Turn the ignition switch off.
Depress the brake pedal 20 times or more to release the pressure in the accumulator.
- When the pressure is released, the brake pedal stroke becomes longer.
Check that the brake fluid level is at the MAX level.
Chock the 4 wheels and release the parking brake.
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).
Start the engine after the brake boost pump stops.
Check that the ABS warning light and slip indicator light are not illuminated.
Turn off the engine, and then turn the ignition switch to ON.
Check that the brake boost pump operates and then stops when the brake pedal is depressed 4 or 5 times.
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).
Check that the brake warning light illuminates and the buzzer sounds when the brake pedal is fully depressed continuously 15 to 20 times.
- Wait 120 seconds or more after turning the ignition switch to ON before performing this inspection.
Check brake booster operation.
Turn the ignition switch off.
Depress the brake pedal 20 times or more to release the pressure in the accumulator.
- When the pressure is released, the brake pedal stroke becomes longer.
Depress the brake pedal, start the engine, and check the change in the brake pedal height.
- OK:
- The brake pedal moves slightly inward.
Inspect brake master cylinder fluid pressure change (for LHD: , for RHD: ).
| 3.READ VALUE USING GTS (ACCUMULATOR SENSOR) |
Connect the GTS to the DLC3.
Turn the ignition switch to ON.
Enter the following menus: Chassis / ABS/VSC/TRC / Data List.
ABS/VSC/TRC| 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. |
Check that the accumulator output value is normal.
- OK:
- Accumulator pressure sensor value is normal.
Result| Result | Proceed to |
| OK | A |
| NG (for LHD) | B |
| NG (for RHD) | C |
| | REPLACE MASTER CYLINDER SOLENOID ()
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| | REPLACE MASTER CYLINDER SOLENOID ()
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Check if the same DTC is output ().
Result| Result | Proceed to |
| DTC is not output | A |
| DTC is output (for LHD) | B |
| DTC is output (for RHD) | C |
| | REPLACE MASTER CYLINDER SOLENOID ()
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| | REPLACE MASTER CYLINDER SOLENOID ()
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| A | |
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| CHECK FOR INTERMITTENT PROBLEMS ()
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| 5.INSPECT BRAKE BOOSTER PUMP ASSEMBLY |
Remove the hydraulic brake booster assembly (for LHD: , for RHD: ).
Using a screwdriver, remove the 2 screws and pull out the wire harness from the master cylinder solenoid.
Measure the resistance according to the value(s) in the table below.
- 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 |
Install the pump motor wire harness to the master cylinder solenoid with the 2 screws (for LHD: , for RHD: ).
Result| Result | Proceed to |
| OK (for LHD) | A |
| OK (for RHD) | B |
| NG (for LHD) | C |
| NG (for RHD) | D |
| | REPLACE HYDRAULIC BRAKE BOOSTER ASSEMBLY ()
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| | REPLACE BRAKE BOOSTER WITH ACCUMULATOR PUMP ASSEMBLY ()
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| | REPLACE BRAKE BOOSTER WITH ACCUMULATOR PUMP ASSEMBLY ()
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| A | |
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| REPLACE HYDRAULIC BRAKE BOOSTER ASSEMBLY ()
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