Lexus NX: Hydraulic Control System Malfunction (C1214)

DESCRIPTION

The skid control ECU (brake booster with master cylinder assembly) controls braking force according to the hybrid control system regenerative braking force and provides the hydraulic pressure necessary for operating each wheel cylinder according to the wheel cylinder pressure sensor.

DTCs may be stored if one of the following occurs:

DTC No.	Detection Item	INF Code	DTC Detection Condition	Trouble Area	Note
C1214	Hydraulic Control System Malfunction	431 432 433 434 435 436 437 438	INF Code: 431 Decrease in hydraulic pressure control performance. (Pressure increase malfunction) INF Code: 432 Decrease in hydraulic pressure control performance. (Pressure decrease malfunction) INF Code: 433 Malfunctions such as leaks occur in the SLA valve. INF Code: 434, 435 Malfunctions such as leaks occur in the SLR valve. INF Code: 436, 437 Decrease in hydraulic pressure control performance. INF Code: 438 Malfunctions such as leaks occur in a hydraulic circuit valve.	INF Code: 431, 432, 433, 434, 435, 436, 437 Brake fluid leaks Brake disc rotor excessive wear Brake actuator (Brake booster with master cylinder assembly) INF Code: 438 Brake actuator (Brake booster with master cylinder assembly)	-

CAUTION / NOTICE / HINT

NOTICE:

When replacing the brake actuator (brake booster with master cylinder assembly), perform initialization and calibration of the linear solenoid valve.

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HINT:

When C1364 is output together with C1214, inspect and repair the trouble areas indicated by C1364 first.

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PROCEDURE

1.	CHECK FOR FLUID LEAK

(a) Check that there are no fluid leaks in the brake lines between the brake actuator (brake booster with master cylinder assembly) and the wheel cylinders.

(b) Check that the brakes are not dragging.

OK:

There are no fluid leaks or dragging.

NG

REPAIR OR REPLACE APPLICABLE PART

OK

2.	CHECK BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY (ACTUATOR SIDE)

(a) Make sure that there is no looseness at the locking part and the connecting part of the connector.

(b) Disconnect the A57 skid control ECU (brake booster with master cylinder assembly) connector 2 minutes after the power switch is turned off.

(c) Check both the connector body and the terminals for deformation and corrosion.

OK:

No deformation or corrosion.

NG

REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY

OK

3.	PERFORM AIR BLEEDING

(a) Reconnect the A57 skid control ECU (brake booster with master cylinder assembly) connector.

(b) Clear the DTCs.

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Chassis > ABS/VSC/TRAC > Clear DTCs

(c) Perform the air bleeding procedure in Bleed Brake System.

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NEXT

4.	CHECK HARNESS AND CONNECTOR (VEHICLE SIDE)

(a) Disconnect the A57 skid control ECU (brake booster with master cylinder assembly) connector.

(b) Measure the voltage and resistance on the wire harness side.

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OK:

Voltage and resistance readings are all normal.

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

5.	READ VALUE USING TECHSTREAM (WHEEL CYLINDER PRESSURE SENSOR)

(a) Reconnect the A57 skid control ECU (brake booster with master cylinder assembly) connector.

(b) Connect an LSPV gauge set.

(c) Connect the Techstream to the DLC3.

(d) Turn the power switch on (IG).

(e) Select the Data List on the Techstream.

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Chassis > ABS/VSC/TRAC > Data List

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

Chassis > ABS/VSC/TRAC > Data List

Tester Display
Wheel Cylinder Pressure Sensor

(f) Check the output values of the wheel cylinder pressure sensor at each hydraulic pressure level during electronically controlled brake system control.

Standard Voltage:

for Front Wheel Cylinder LH

Hydraulic Pressure (MPa (kgf/cm2, psi))	Wheel Cylinder Pressure Sensor (V)
2.0 (20.4, 290)	0.53 to 1.33
5.0 (51.0, 725)	1.12 to 1.92
7.0 (71.4, 1015)	1.52 to 2.32
10.0 (102.0, 1451)	2.14 to 2.94

for Front Wheel Cylinder RH

Hydraulic Pressure (MPa (kgf/cm2, psi))	Wheel Cylinder Pressure Sensor (V)
2.0 (20.4, 290)	0.53 to 1.33
5.0 (51.0, 725)	1.12 to 1.92
7.0 (71.4, 1015)	1.52 to 2.32
10.0 (102.0, 1451)	2.14 to 2.94

NG

REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY

OK

6.	CHECK BRAKE DISC

(a) Turn the power switch off.

(b) Disconnect the A53 brake pedal stroke sensor assembly connector.

(c) 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.

NG

REPLACE BRAKE DISC

OK

7.	RECONFIRM DTC

(a) Reconnect the A53 brake pedal stroke sensor assembly connector.

(b) Clear the DTCs.

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Chassis > ABS/VSC/TRAC > Clear DTCs

(c) Perform a road test under the same malfunction conditions recreated based on the Freeze Frame Data or customer problem analysis.

(d) Check if the same DTC is output.

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Chassis > ABS/VSC/TRAC > Trouble Codes

Result	Proceed to
DTC C1214 is not output.	A
DTC C1214 is output.	B

HINT:

If the DTC is no longer output, it can be suspected that it was output due to an improperly connected connector.

A

USE SIMULATION METHOD TO CHECK

B

REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY

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