C1285 Vacuum 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] CHECK VACUUM HOSE

1. Turn the ignition switch off.
2. Check the vacuum hose.
   　 OK: No cracks or damage on the vacuum hoses.
   

REPLACE VACUUM HOSE

[3] INSPECT VACUUM SENSOR

1. Remove the No. 1 and No. 2 vacuum sensors.
2. Connect 3 dry batteries of 1.5 V in series.
3. Connect the VC terminal to the battery's positive (+) terminal and the E2 terminal to the battery's negative (-) terminal. Then apply about 4.5 V between the VC and E2 terminals.
   
   
   Do not apply 6 V or more to terminals VC and E2.
   
   　
4. Connect a voltmeter to terminals PIM and E2 of the sensor, and measure the output voltage at atmospheric pressure.

5. Apply a vacuum to the vacuum sensor in 20 kPa (0.2 kgf/ cm2, 2.9 psi) in increments to 100 kPa (1.02 kgf/cm2, 14.51 psi).

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

   Tester Connection	Front Brake Pressure kPa (kgf/cm2, psi)	Specified Condition
   2 (PIM) - 1 (E2)	20 (0.2, 2.9)	0.5 V
   2 (PIM) - 1 (E2)	60 (0.61, 8.7)	2.4 V
   2 (PIM) - 1 (E2)	100 (1.02, 14.51)	3.6 V

7. Check the difference of voltage between the vacuum sensors.
   
   OK: Difference is 340 mV or more.
   
   Check the vacuum sensor signal after replacement (See TEST MODE PROCEDURE)

REPLACE VACUUM SENSOR

[4] CHECK HARNESS AND CONNECTOR (SKID CONTROL ECU - VACUUM SENSOR)

1. Install the vacuum sensor.
2. Disconnect the skid control ECU connector and the vacuum sensor connector.
3. Measure the resistance according to the value (s) in the table below.
   
   Standard resistance:

   Tester Connection	Condition	Specified Condition
   S12-11 (E4) - V1-1 (E2)	Always	Below 1Ω
   S12-11 (E4) - Body ground	Always	10 kΩ or higher
   S12-10 (PIM) - V1-2 (PIM)	Always	Below 1Ω
   S12-10 (PIM) - Body ground	Always	10 kΩ or higher
   S12-21 (VCP) - V1-3 (VC)	Always	Below 1Ω
   S12-21 (VCP) - Body ground	Always	10 kΩ or higher
   S12-13 (E3) - V2-1 (E2)	Always	Below 1Ω
   S12-13 (E3) - Body ground	Always	10 kΩ or higher
   S12-23 (PIM2) - V2-2 (PIM)	Always	Below 1Ω
   S12-23 (PIM2) - Body ground	Always	10 kΩ or higher
   S12-22 (VCP2) - V2-3 (VC)	Always	Below 1Ω
   S12-22 (VCP2) - 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 voltage:

   Tester Connection	Switch Condition	Specified Condition
   S12-21 (VCP) - Body ground	Ignition switch ON	4.75 to 5.25 V
   S12-22 (VCP2) - Body ground	Ignition switch ON	4.75 to 5.25 V

REPLACE SKID CONTROL ECU

[6] RECONFIRM DTC

1. Reconnect the vacuum sensor.
2. Clear the DTC (See Pub. No. S1-YXZE05A, page 05-108).
3. 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).
4. Check if the same DTC is recorded (See Pub. No. S1-YXZE05A, page 05-108).
   
   Result: 　

   Result	Proceed to
   DTC (C1265/65) is not output	A
   DTC (C1265/65) is output	B

   
   
   If troubleshooting has been carried out according to the Problem Symptoms Table, refer back to the table and proceed to the next step (See PROBLEM SYMPTOMS TABLE).
   

A REPLACE SKID CONTROL ECU

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

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

   Tester Connection	Switch 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

   
   
   If troubleshooting has been carried out according to the Problem Symptoms Table, refer back to the table and proceed to the next step (See PROBLEM SYMPTOMS TABLE).
   

REPAIR OR REPLACE HARNESS OR CONNECTOR (STP CIRCUIT)

REPLACE SKID CONTROL ECU

1. Confirm the DTC C1285 is inactive

   • Start the engine and let it idling condition.
   • Verify the DTC C1285 is inactive.

   

2. DTC Clear

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

   

C1285 is reoccur: Return to first process Other DTC appear: Refer to concerned Trouble shooting

Complete