DTC C1246/46 Master Cylinder Pressure Sensor Malfunction; DTC C1281/81 Master Cylinder Pressure Sensor Output Malfunction (Test Mode DTC): Wiring Diagram

1. Check that the stop light comes on when the brake pedal is depressed, and goes off when the brake pedal is released.

   OK 

   CONDITION CHART
   
   

   Condition	Illumination Condition
   Brake pedal depressed	ON
   Brake pedal released	OFF

NG : INSPECT STOP LIGHT CIRCUIT 

OK : GO TO NEXT STEP 

1. Connect the intelligent tester to the DLC3.
2. Start the engine.
3. Select the Data List mode on the intelligent tester.

   ABS / VSC: 

   NORMAL CONDITION CHART
   
   

   Item (Display)	Measurement Item / Range (Display)	Normal Condition
   STOP LAMP SW	Stop light switch / ON or OFF	ON: Brake pedal depressed OFF: Brake pedal released

4. Check that the stop light display observed on the intelligent tester changes when the brake pedal is depressed.

   OK: When the brake pedal is depressed, the intelligent tester displays "ON". 

OK : Go to step   4 

NG : GO TO NEXT STEP 

1. Disconnect the skid control ECU connector.
2. Measure the voltage according to the value(s) in the table below.

   Standard voltage 

   TESTER CONNECTION AND SPECIFIED CONDITION CHART
   
   

   Tester Connection	Condition	Specified Condition
   J77-10 (STP11) - Body ground	Stop light switch ON (Brake pedal depressed)	8 to 14 V
   J77-10 (STP11) - Body ground	Stop light switch OFF (Brake pedal released)	Below 1.5 V

   Fig 2: Inspecting Skid Control ECU (STP1 Terminal)

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

NG : REPAIR OR REPLACE HARNESS OR CONNECTOR (STP1 CIRCUIT) 

OK : REPLACE SKID CONTROL ECU 

1. Select the Data List mode on the intelligent tester.

   ABS / VSC: 

   NORMAL CONDITION CHART
   
   

   Item (Display)	Measurement Item / Range (Display)	Normal Condition
   MAS CYL PRESS 1	Master cylinder pressure sensor 1 reading / min.: 0 V, max.: 5 V	When brake pedal is released: 0.3 to 0.9 V

2. Check that the brake fluid pressure value of the master cylinder pressure sensor observed on the intelligent tester changes when the brake pedal is depressed.

   OK: When the pedal is depressed, voltage displayed on the intelligent tester increases. 

OK : Go to step   8 

NG : GO TO NEXT STEP 

1. Turn the engine switch off.
2. Disconnect the skid control ECU connector and the brake actuator connector.
3. Measure the resistance according to the value(s) in the table below.

   Standard resistance 

   TESTER CONNECTION AND SPECIFIED CONDITION CHART
   
   

   Tester Connection	Condition	Specified Condition
   J78-18 (VCM) - A13-20 (VCM)	Always	Below 1 Ω
   J78-18 (VCM) - Body ground	Always	10 kΩ or higher
   J78-4 (PMC) - A13-17 (PMC)	Always	Below 1 Ω
   J78-4 (PMC) - Body ground	Always	10 kΩ or higher
   J78-6 (E2) - A13-19 (E2)	Always	Below 1 Ω
   J78-6 (E2) - Body ground	Always	10 kΩ or higher

   Fig 3: Checking Harness And Connector (Skid Control ECU - Brake Actuator Assembly)

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

NG : REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK : GO TO NEXT STEP 

1. Reconnect the skid control ECU connector.
2. Turn the engine switch on (IG).
3. Measure the voltage according to the value(s) in the table below.

   Standard voltage 

   TESTER CONNECTION AND SPECIFIED CONDITION CHART
   
   

   Tester Connection	Condition	Specified Condition
   J78-18 (VCM) - Body ground	Engine switch on (IG)	4.5 to 5.5 V

   Fig 4: Inspecting Skid Control ECU (Sensor Input)

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

NG : REPLACE SKID CONTROL ECU 

OK : GO TO NEXT STEP 

1. Reconnect the brake actuator connector.
2. Remove either the right or left front brake cylinder bleeder plug.
3. Install the pressure gauge via the attachment, and bleed the gauge of air (See BLEEDING ).
4. Measure the voltage according to the value(s) in the table below.

   Standard voltage 

   TESTER CONNECTION AND SPECIFIED CONDITION CHART
   
   

   Tester Connection	Fluid Pressure MPa (kgf/cm2 , psi)	Specified Condition
   J78-4 (PMC) - Body ground	0 (0, 0)	0.37 to 0.63 V
   J78-4 (PMC) - Body ground	5.88 (60, 853)	1.57 to 1.83 V
   J78-4 (PMC) - Body ground	11.8 (120, 1,707)	2.77 to 3.03 V

   Fig 5: Inspecting Skid Control ECU (Sensor Output)

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

NG : REPLACE BRAKE ACTUATOR ASSEMBLY 

OK : GO TO NEXT STEP 

1. Turn the engine switch off.
2. Clear the DTC (See DTC CHECK / CLEAR  ).
3. Start the engine.
4. At a speed of 18 mph (30 km/h) or more, drive the vehicle and perform braking test (decelerate the vehicle by depressing the brake pedal).
5. Check if the same DTC is recorded (See DTC CHECK / CLEAR  ).

   Result 

   CONDITION CHART
   
   

   Condition	Proceed to
   DTC (C1246/46) is not output	A
   DTC (C1246/46) is output	B

B : REPLACE SKID CONTROL ECU 

A : USE SIMULATION METHOD TO CHECK