MALFUNCTION OF DIFFERENTIAL PRESSURE SENSOR [LO]
(DTC CODE P1427 / DIAGNOSIS MONITOR CODE 28)

1. Set the starter key to the "LOCK" position and disconnect the differential pressure sensor connector.
2. Measure resistance between the 1st and 3rd terminals of the differential pressure sensor connector (component side).

   
   

   
   

   Standard value: 2 Ω or less

3. Measure resistance between the 1st and 2nd terminals of the differential pressure sensor conne ctor (component side).

Standard value: 2 Ω or less

NO Fault in DPR differential pressure sensor	YES Proceed to [2] Measuring resistance between terminals

1. Set the starter key to the "LOCK" position and disconnect the engine ECU connector.
2. Measure resistance between the chassis GND and the 3rd terminal of the DPR differential pressure sensor connector (vehicle harness side).

   
   

   
   

   Standard value: ∞ Ω

3. Measure resistance between the chassis GND and the 2nd terminal of the DPR differential pressure sensor connector (vehicle harness side).

Standard value: ∞ Ω

NO Faulty harness	YES Proceed to [3] Measuring resistance between terminals

1. Connect the signal check harness and measure resistance between the terminal V71 and the chassis GND.

   

    

   ECU terminal No.	Description of terminal
   V71	Sensor +B

   Standard value: ∞ Ω

2. Measure resistance between the terminal V70 and the chassis GND.

ECU terminal No.	Description of terminal
V70	Differential pressure sensor SIG

Standard value: ∞ Ω

NO Faulty harness	YES Proceed to [4] Measuring resistance between terminals

1. Disconnect the signal check harness connectors from the ECU.
2. Measure resistance between the terminals V71 and V79.

   

   ECU terminal No.	Description of terminal
   V71	Sensor +B
   V80	Sensor GND

   Standard value: 2 Ω or less

3. Measure resistance between the terminals V70 and V80.

   

   ECU terminal No.	Description of terminal
   V70	Differential pressure sensor SIG
   V80	Sensor GND

   Standard value: ∞ Ω

NO Faulty harness or irregular contact of connector	YES Proceed to [5] Measuring resistance between terminals

1. Set the starter key to the "LOCK" position and connect the signal check harness connectors to the ECU.
2. Measure resistance between the terminals V70 and V71.
   

   

   ECU terminal No.	Description of terminal
   V70	Differential pressure sensor SIG
   V71	Sensor +B

   Standard value: 200-250 kΩ

NO Fault in engine ECU	YES Proceed to [6] Measuring voltage between terminals

1. Turn the starter key ON.
2. Measure voltage between the terminals V71 and V80.
   

   

   ECU terminal No.	Description of terminal
   V71	Sensor +B
   V80	Sensor GND

   Standard value: 4.5-5.5 V

NO Fault in engine ECU	YES Use HINO-DX to delete past malfunctions and then output diagnosis codes again.

1. Confirm the DTC P1427 is inactive

   • Start the engine and let it idling condition.
   • Verify the DTC P1427 is inactive.

   

2. DTC Clear

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

   

P1427 is reoccur: Return to first process Other DTC appear: Refer to concerned Trouble shooting

Complete