Toyota Tundra Service Manual: Master Cylinder Pressure Sensor Malfunction (C1246)

DESCRIPTION

The master cylinder pressure sensor is connected to the skid control ECU in the brake actuator assembly.

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

C1246

Master Cylinder Pressure Sensor Malfunction

When the skid control ECU receives a master cylinder pressure sensor power source malfunction signal.

  • Stop light switch assembly circuit
  • Master cylinder pressure sensor circuit
  • Master cylinder pressure sensor (brake actuator assembly)

WIRING DIAGRAM

Refer to DTC C1249.

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CAUTION / NOTICE / HINT

NOTICE:

When replacing the skid control ECU (brake actuator assembly), perform system variant learning and acceleration sensor zero point calibration.

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PROCEDURE

1.

READ VALUE USING TECHSTREAM (STOP LIGHT SWITCH ASSEMBLY)

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch to ON.

(c) Enter the following menus: Chassis / ABS/VSC/TRAC / Data List.

ABS/VSC/TRAC

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

Stop Light SW

Stop light switch assembly

ON or OFF

ON: Brake pedal depressed

OFF: Brake pedal released

-

(d) Check that the stop light switch assembly display observed on the Techstream changes according to brake pedal operation.

OK:

The Techstream displays on or off according to brake pedal operation.

NG

GO TO STEP 4

OK

2.

READ VALUE USING TECHSTREAM (MASTER CYLINDER PRESSURE SENSOR)

(a) Start the engine.

(b) Enter the following menus: Chassis / ABS/VSC/TRAC / Data List.

ABS/VSC/TRAC

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

Master Cylinder Sensor

Master cylinder pressure sensor reading

Min.: 0.00 V, Max.: 5.00 V

Brake pedal released: 0.20 to 0.40 V

Reading increases when brake pedal is depressed

(c) Check that the value of the master cylinder pressure sensor observed on the Techstream changes when the brake pedal is depressed.

OK:

When the brake pedal is depressed, the voltage displayed on the Techstream increases.

NG

REPLACE BRAKE ACTUATOR ASSEMBLY

OK

3.

RECONFIRM DTC

(a) Clear the DTCs.

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(b) Turn the ignition switch off.

(c) Start the engine.

(d) Drive the vehicle at a speed 6 km/h (3.7 mph) or more and depress the brake pedal several times to test the stop light circuit.

(e) Check if the same DTC is output.

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Result

Proceed to

C1246 is not output

A

C1246 is output

B

A

USE SIMULATION METHOD TO CHECK

B

REPLACE BRAKE ACTUATOR ASSEMBLY

4.

CHECK HARNESS AND CONNECTOR (STP TERMINAL)

(a) Turn the ignition switch off.

*a

Front view of wire harness connector

(to Skid Control ECU (Brake Actuator Assembly))

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

OK:

The connector is securely connected.

(c) Disconnect the A57 skid control ECU (brake actuator assembly) connector.

(d) Check both the connector case and the terminals for deformation and corrosion.

OK:

No deformation or corrosion.

(e) Measure the voltage according to the value(s) in the table below.

Standard Voltage:

Tester Connection

Condition

Specified Condition

A57-2 (STP) - Body ground

Stop light switch assembly on (Brake pedal depressed)

8 to 14 V

A57-2 (STP) - Body ground

Stop light switch assembly off (Brake pedal released)

Below 1.5 V

OK

REPLACE BRAKE ACTUATOR ASSEMBLY

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (STP CIRCUIT)

    Acceleration Sensor Stuck Malfunction (C1243)

    Open in Stop Light Switch Circuit (C1249)

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