Hino P20E9 Fault Code: Back flow line and pressure line pressure check

TECHNICAL DESCRIPTION

• DEF line pressure depends on flow quantity of DEF pump.
• DEF pump flow quantity is determined by the value supplied from the DEF pressure sensor which is integrated with the DEF pump.

DESCRIPTION OF MALFUNCTION

Abnormal pressure in the DEF pipe is detected.

DTC SET CONDITION

DTC Detection Condition:

• Exhaust gas temperature (SCR inlet) > 150°C {302°F}
• Defrosting DEF is done.
• DEF pressure build up-to 650 kPa {94 psi} is successfully completed.

Judgment Criteria:

During “Detection Mode”: 

• DEF line pressure does not decrease or is stable at more than 1,000 kPa {145.0 psi} for 2 seconds at 7% of DEF pump opening. 
• DEF pressure was not stable for 8 seconds from 850 to 950 kPa {123.3 to 137.8 psi} in detection mode (300 seconds). 

After “DEF Injection Start”: 

DEF line pressure is more than 1,250 kPa {181.3 psi} for 5 sec.

RESET CONDITION

After having restored to the normal conditions.

INDICATION, WARNING OR SYSTEM CONTROL REGULATION WHEN THE DTC IS SET

• MIL: ON 
• SCR malfunction light: ON 
• DEF injection is stopped. 
• NOx reduction quantity monitoring is aborted. 
• If malfunction does not improve within 500 miles: engine output is restricted. 
• If malfunction does not improve within 2,000 miles: vehicle speed is restricted.

SYMPTOMS ON THE VEHICLE WHEN THE DTC IS SET

Symptoms on the Vehicle Due to Backup Control (Fail Safe Function):

• NOx reduction function is prevented. 
• Engine output is insufficient (when malfunction does not improve within 500 miles) 
• Vehicle does not speed up (when malfunction does not improve within 2,000 miles)

PRE-INSPECTION WORK

• Check that the battery voltage is in the normal range.

AFTER-INSPECTION WORK

• Clear all past DTCs.
• Reset “Ure SCR related memory”
• Check that no DTC is detected after test drive.

POSSIBLE CAUSES

• DEF in the DEF tank is empty. 
• Strainer in the DEF sensor is clogged. 
• Air is entering into DEF suction line. 
• DEF suction line is clogged (frozen), or DEF leaks from DEF suction line. 
• DEF pump filter element is clogged. 
• DEF pump inlet connector is clogged. 
• DEF pump back flow connector is clogged. 
• DEF back flow line is clogged. 
• Leak from DEF pump. 
• DEF pump malfunction. 
• Clogged DEF tank breather hose.

NOTE: DEF-SCR system can be damaged by Diesel filling up to the tank. If DEF pump main filter has a yellow slime, it is an evidence of biodiesel filled to the tank.

INSPECTION PROCEDURE

TROUBLESHOOTING STEPS

Step 1) Check the DEF pressure ramping up curve.

1. Set the starter switch to the “LOCK” position.
2. Connect the vehicle to the diagnostic tool.
3. Set the starter switch to the “ON” position.
4. Select [Engine].
5. Select “DPR deposition quantity” from the customization items and change the PM deposition quantity to [3.0 g/L].
6. Exit from [Engine] and connect to [DCU] on the diagnostic tool menu.
7. Select [DEF pump pressure] in [Data monitor Setting] and read (record) the data (values) during DPR manual regeneration. (Start the monitor and then push the DPR manual regeneration button.)
8. After manual regeneration completed, stop monitoring and save the data.
9. Using the data collected for the DEF pressure, check for the following conditions:

• Condition (1): Pressure raises over 1,000 kPa {145.0 psi} for more than 2 seconds. 
• Condition (2): Pressure raises up and does not drop. 
• Condition (3): Pressure raises over 1,250 kPa {181.3} for more than 5 seconds.

Is the condition (1), (2) or (3) found in the corrected data?

Step 2) Inspect the DEF backflow line.

1. Set the starter switch to the “LOCK” position.
2. Disconnect the DEF hose (backflow line) between the DEF tank and the DEF pump.
3. Blow air from upstream side (DEF pump side) of the DEF hose and check if the hose is clogged.
4. Remove the DEF pick-up unit (DEF sensor) from the DEF tank.
5. Blow air from upstream side (DEF hose side) of the DEF connector on the DEF sensor and check if the connector/pipe is clogged.

Was any failure found?

Step 3) Inspect the DEF backflow line.

• Replace the DEF pump backflow connector to new one, then perform same test with Step 1 again.
• Tightening Torque for Connector: 4.0 – 5.0 N·m {41 – 51 kgf·cm, 3.0 – 3.6 lbf·ft}.

Is the condition (1), (2) or (3) found in the corrected data?

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