C1246 Master Cylinder Pressure Sensor Malfunction

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	Illumination Condition
   Brake pedal depressed	ON
   Brake pedal released	OFF

INSPECT STOP LIGHT CIRCUIT

[2] RECONFIRM DTC

1. Turn the ignition switch off.
2. Clear the DTC (See Pub. No. S1-YXZE05A, page 05-108).
3. Start the engine.
4. At a speed of 10 km/h (6 mph) 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 Pub. No. S1- YXZE05A, page 05-108).
   
   Result: 　

   Result	Proceed to
   DTC (C1246) is not output	A
   DTC (C1246) is output	B

A CHECK FOR INTERMITTENT PROBLEMS (SYMPTOM SIMULATION) (See DIAGNOSIS SYSTEM)

B REPLACE SKID CONTROL ECU

1. Measure the voltage according to the value (s) in the table below.
   
   Standard voltage:

   Tester Connection	Switch Condition	Specified Condition
   3 (VCM) - 1 (E2)	Ignition switch ON	4.75 to 5.25 V

2. Install the hydro LSPV gauge (SST) and bleed air.
3. Start the engine.
4. Measure the voltage according to the value (s) in the table below.
   
   Standard voltage:

   Tester Connection	Fluid Pressure MPa (kgf/cm2, psi)	Specified Condition
   2 (PMC) - 1 (E2)	0 (0, 0)	0.5 V
   2 (PMC) - 1 (E2)	9.8 (100, 1422)	2.5 V
   2 (PMC) - 1 (E2)	19.6 (200, 2844)	4.5 V

   
   
   Check the master cylinder pressure sensor signal after replacement (See TEST MODE PROCEDURE)
   

REPLACE MASTER CYLINDER PRESSURE SENSOR

[4] CHECK HARNESS AND CONNECTOR (SKID CONTROL ECU - MASTER CYLINDER PRESSURE SENSOR)

1. Turn the ignition switch off.
2. Disconnect the skid control ECU connector and the master cylinder pressure sensor connector.
3. Measure the resistance according to the value (s) in the table below.
   
   
   Standard resistance: 　

   Tester Connection	Condition	Specified Condition
   S12-24 (VCM) - M1-3 (VCM)	Always	Below 1 Ω
   S12-24 (VCM) - Body ground	Always	10 kΩ or higher
   S12-25 (PMC1) - M1-2 (PMC)	Always	Below 1 Ω
   S12-25 (PMC1) - Body ground	Always	10 kΩ or higher
   S12-15 (E2) - M1-1 (E2)	Always	Below 1 Ω
   S12-15 (E2) - Body ground	Always	10 kΩ or higher

REPAIR OR REPLACE HARNESS OR CONNECTOR

[5] INSPECT SKID CONTROL ECU (SENSOR INPUT)

1. Reconnect the skid control ECU connector.
2. Turn the ignition switch to the ON position.
3. Measure the voltage according to the value (s) in the table below.
   
   Standard: 　

   Tester Connection	Switch Condition	Specified Condition
   S12-24 (VCM) - Body ground	Ignition switch ON	4.75 to 5.25 V

REPLACE SKID CONTROL ECU

[6] INSPECT SKID CONTROL ECU (SENSOR OUTPUT)

1. Turn the ignition switch off.
2. Reconnect the master cylinder pressure sensor connector.
3. Turn the ignition switch to the ON position.
4. Measure the voltage according to the value (s) in the table below.
   
   Standard voltage:
   　

   Tester Connection	Condition	Specified Condition
   S12-25 (PMC1) - Body ground	Ignition switch ON, brake pedal released	0.3 to 0.7 V

   
   
   Check the master cylinder pressure sensor signal after replacement (See TEST MODE PROCEDURE)
   

REPLACE MASTER CYLINDER PRESSURE SENSOR

[7] RECONFIRM DTC

1. Turn the ignition switch off.
2. Clear the DTC (See Pub. No. S1-YXZE05A, page 05-108).
3. Start the engine.
4. At a speed of 10 km/h (6 mph) 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 Pub. No. S1- YXZE05A, page 05-108).
   
   Result: 　

   Result	Proceed to
   DTC (C1246) is not output	A
   DTC (C1246) is output	B

A CHECK FOR INTERMITTENT PROBLEMS (SYMPTOM SIMULATION) (See DIAGNOSIS SYSTEM)

B REPLACE SKID CONTROL ECU

1. Turn the ignition switch off.
2. Disconnect the skid control ECU connector.
3. Measure the voltage according to the value (s) in the table below.
   
   
   Standard voltage: 　

   Tester Connection	Condition	Specified Condition
   S13-1 (STP) - Body ground	Stop light switch ON (Brake pedal depressed)	16 to 32 V
   S13-1 (STP) - Body ground	Stop light switch OFF (Brake pedal released)	Below 3 V

REPAIR OR REPLACE HARNESS OR CONNECTOR (STP CIRCUIT)

REPLACE SKID CONTROL ECU

1. Confirm the DTC C1246 is inactive

   • Start the engine and let it idling condition.
   • Verify the DTC C1246 is inactive.

   

2. DTC Clear

   • Clear the DTC with Hino DX
   • Confirm the same DTC is not reoccurred

   

C1246 is reoccur: Return to first process Other DTC appear: Refer to concerned Trouble shooting

Complete