DTC Code | DTC Name |
---|---|
C120F | Open in Master Reservoir Level Switch Circuit |
DESCRIPTION
If the skid control ECU (brake booster with master cylinder assembly) detects that the brake fluid level is low or there is an open in the brake fluid level warning switch signal circuit, DTC C120F is stored.
DTC No. | Detection Item | INF Code | DTC Detection Condition | Trouble Area | Note |
---|---|---|---|---|---|
C120F | Open in Master Reservoir Level Switch Circuit | 371 | The brake fluid level warning switch (brake booster with master cylinder assembly) circuit is open for 2 seconds or more. |
|
Electronically controlled brake system DTC |
CAUTION / NOTICE / HINT
Note
After replacing the skid control ECU (brake booster with master cylinder assembly), perform linear solenoid valve offset learning, ABS holding solenoid valve learning, yaw rate and acceleration sensor zero point calibration and system information memorization after performing "Reset Memory".
PROCEDURE
CHECK BRAKE FLUID LEVEL
Check that the brake fluid level is sufficient.
Tech Tips
If the fluid level is low, check for fluid leaks, and repair as necessary.
Check for brake fluid leaks (connection between the brake booster pump assembly, brake actuator assembly, brake booster with master cylinder assembly and wheel cylinders).
Check that the DTC is not output again.
Check that there are no leaks from the connections between the brake booster pump assembly, brake actuator assembly and brake booster with master cylinder assembly.
Tech Tips
As a visual check is very difficult, perform the check with the following procedure.
Bleed the air from the brake system.
Turn the power switch off.
Disconnect the A36 brake pedal stroke sensor assembly connector.
Select the Data List on the GTS.
Tester Display | Measurement Item | Range | Normal Condition | Diagnostic Note |
---|---|---|---|---|
MT Voltage Value | MT voltage value | Min.: 0.00 V, Max.: 20.00 V | Pump motor off: 0.00 V Pump motor on: 12.00 V |
- |
Accumulator Pressure | Accumulator pressure output value | Min.: 0.00 MPa, Max.: 24.48 MPa | 15.00 to 21.00 MPa (Pressure stable and pump motor stopped) |
When brake fluid is stored in the accumulator: Accumulator pressure changes in accordance with volume of fluid stored in the accumulator |
Tester Display |
---|
MT Voltage Value |
Accumulator Pressure |
Depress the brake pedal several times to operate the pump motor, then wait until it stops.
After the pump motor stops, wait for 30 seconds, then check the drop in the accumulator pressure sensor output value and the state of the pump motor.
Result | ||||||
---|---|---|---|---|---|---|
|
B |
CHECK AND REPAIR BRAKE FLUID LEAKS OR ADD FLUID |
A |
INSPECT BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY (BRAKE FLUID LEVEL WARNING SWITCH)
*a | Component without harness connected (Brake Fluid Level Warning Switch (Brake Booster with Master Cylinder Assembly)) |
Turn the power switch off.
Reconnect the A36 brake pedal stroke sensor assembly connector.
Remove the brake master cylinder reservoir filler cap assembly.
Make sure that there is no looseness at the locking part and the connecting part of the connector.
OK |
---|
The connector is securely connected. |
Disconnect the A35 brake fluid level warning switch (brake booster with master cylinder assembly) connector.
Check both the connector case and the terminals for deformation and corrosion.
OK |
---|
No deformation or corrosion. |
Measure the resistance according to the value(s) in the table below.
Tech Tips
A float is located inside the brake master cylinder reservoir assembly (brake booster with master cylinder assembly). Its position changes according to the level of brake fluid.
Standard Resistance | |||||||||
---|---|---|---|---|---|---|---|---|---|
|
Tech Tips
If there are no problems after completing the preceding inspection, adjust the brake fluid to the MAX level with the power switch on (IG).
Result | |||
---|---|---|---|
|
NG |
REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY for LHD: Click here |
OK |
CHECK HARNESS AND CONNECTOR (BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY - BRAKE FLUID LEVEL WARNING SWITCH (BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY))
Turn the power switch off.
Make sure that there is no looseness at the locking part and the connecting part of the connector.
OK |
---|
The connector is securely connected. |
Disconnect the A32 skid control ECU (brake booster with master cylinder assembly) connector.
Check both the connector case and the terminals for deformation and corrosion.
OK |
---|
No deformation or corrosion. |
Measure the resistance according to the value(s) in the table below.
Standard Resistance | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
|
Result | |||
---|---|---|---|
|
NG |
REPAIR OR REPLACE HARNESS OR CONNECTOR |
OK |
CHECK BRAKE DISC
Reconnect the A32 skid control ECU (brake booster with master cylinder assembly) connector.
Reconnect the A35 brake fluid level warning switch (brake booster with master cylinder assembly) connector.
Disconnect the A36 brake pedal stroke sensor assembly connector.
Perform a road test according to Freeze Frame Data or customer problem analysis. While driving, check for abnormal brake pedal vibration caused by brake discs that are worn or have excess runout.
OK |
---|
Brake pedal does not vibrate during braking. |
Tech Tips
An unevenly worn disc may vibrate the caliper pistons and cause fluctuations in brake line pressure, triggering a malfunction detection condition.
The brake pedal does not kick back due to caliper piston vibration during electronically controlled brake system control.
If the brake pedal stroke sensor assembly connector is disconnected, the fail-safe function will prohibit electronically controlled brake system control.
The Active Test does not prohibit electronically controlled brake system control when the vehicle is being driven, so disconnect the brake pedal stroke sensor assembly connector before continuing with inspection.
Uneven disc wear can be checked by measuring the disc thickness variation.
for Front Brake: Click here
for Rear Brake: Click here
Result | |||
---|---|---|---|
|
NG |
REPLACE BRAKE DISC |
OK |
RECONFIRM DTC
Turn the power switch off.
Reconnect the A36 brake pedal stroke sensor assembly connector.
Clear the DTCs.
Turn the power switch off.
Turn the power switch on (READY).
Perform a road test.
Check if the same DTC is output.
Result | ||||||
---|---|---|---|---|---|---|
|
A |
USE SIMULATION METHOD TO CHECK Click here |
B |
REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY for LHD: Click here |