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Hino P20D8 Fault Code: Exhaust fuel doser open/close stuck

07/11/2024

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TECHNICAL DESCRIPTION

− The engine ECU detected sticking of the fuel dosing valve (Fuel addition valve/aftertreatment fuel injector).

DTC SET CONDITION

DTC Detection Condition:

DPR regeneration is in process, or the following conditions remain for 3 seconds.

Engine revolution: 1,000 r/min or more
Exhaust gas temperature sensor 3 (DOC inlet): 260°C {500°F} or more.
Exhaust gas temperature sensor 4 (DPR inlet): 200°C {392°F} or more

Number of times of aftertreatment fuel injection (indicated times of engine ECU): 10 times.

Judgment Criteria:

The number of times of actual fuel injection falls below 30% against the indication of aftertreatment fuel injection.

RESET CONDITION

Immediately after normal status is resumed.

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

MIL: ON
SVS light: OFF

SYMPTOMS ON THE VEHICLE WHEN THE DTC IS SET

Symptoms on the Vehicle Due to Malfunction:

DPR regeneration failure.

PRE-INSPECTION WORK

Check that the battery voltage is in the normal range.

AFTER-INSPECTION WORK

Clear all past DTCs.
Check that no DTC is detected after test drive.

POSSIBLE CAUSES

Fuel leakage (loose joint bolt), clogging, crush, and wrong assembly in fuel pipe (for aftertreatment).
Malfunction of the fuel dosing valve (abnormality in fuel injection quantity).
Abnormality in characteristics of aftertreatment fuel injection line pressure sensor.

INSPECTION PROCEDURE

TROUBLESHOOTING STEPS

Step 1) Check the DTC detected [Diagnostic Tool].

Set the starter switch to the “LOCK” position.
Connect the diagnostic tool to the vehicle.
Set the starter switch to the “ON” position.
Select [Engine] on the screen of the diagnostic tool and check if the DTC P20D8, P20CD, P20CE has been detected.

Has a DTC other than P20D8 been detected?

Yes – Perform the relevant DTC-specific troubleshooting.

No – Go to Step 2.

Step 2) Inspect the fuel pipe (for aftertreatment).

Check if any of the following defects is found in the pipe between the fuel pump and the fuel dosing valve.

− Fuel leakage (loose joint bolt). − Crush. − Wrong assembly.

Bleed air from the fuel pipe and also check that there is no clogging in the pipe.

Inspection Procedure:

Set the starter switch to the “ON” position.
Loosen the joint bolt.
Slowly push the feed pump until fuel comes out.

CAUTION: Use care, as a large amount of fuel may come out if the feed pump is pushed excessively. Were any failures found?

Yes – Repair or replace the defective part. After repair or replacement, bleed air from the pipe and perform DPR manual regeneration.

No – Go to Step 3.

Step 3) Inspect the fuel dosing valve.

Remove the fuel dosing valve and clean the injection hole.

CAUTION:

For details of the cleaning steps, refer to the engine workshop information.
Do not use cloth, etc. for cleaning to prevent clogging.

Install the fuel dosing valve and inspect operation of the fuel dosing valve by using the diagnostic tool.

For detailed procedure, refer to the separate sheet Inspecting operation of the fuel dosing valve. Were any failures found?

Yes – Replace the fuel dosing valve. Clear all past DTCs. Check that no DTC is detected after test drive.

No – Procedure completed. Clear all past DTCs. Check that no DTC is detected after test drive.

INSPECTING OPERATION OF THE FUEL DOSING VALVE

1) Test method.

Connect the diagnostic tool to the vehicle.
Warm up the engine. (Coolant temperature: 80ºC {176 ºF} or more).
Stop the engine and set the starter switch to the “ON” position.
Select [Engine] on the screen of the diagnostic tool, select [Customization] and check [DPR deposit volume].

When the [DPR deposit volume] is 2.5 or more: The value remains unchanged.
When the [DPR deposit volume] is less than 2.5: The value is changed to 2.5.

Start the engine.
On the screen of the diagnostic tool, select [Data monitor setting] and set [DPR exhaust gas temperature (IN)] and [Additional quantity of fuel] (Additive amount of fuel dosing valve) for monitoring.
Turn ON the DPR manual regeneration switch. − The idle r/min increases, and the exhaust brake is actuated. Then, check that the exhaust brake is released and the idle r/min decreases.
Save the values on the “Data monitor” and draw a similar graph by referring to Figure 1.
Read the following from the graph:

Indication of injection for the fuel dosing valve (point A) – With injection indication: Normal, Without injection indication: Abnormal.
Temperature of Exhaust Temperature (IN) (point B) — Single-stage rise: Normal, Two-stage rise: Abnormal