ENGINE (DIAGNOSTICS)(H4DOTC DIESEL) > Diagnostic Procedure without Diagnostic Trouble Code (DTC)

CAUTION:

After servicing or replacing faulty parts, perform Clear Memory Mode , and Inspection Mode .

WIRING DIAGRAM:

STEP

CHECK

YES

1.CHECK DTC.

Read DTC using Subaru Select Monitor or general scan tool.

NOTE:

• Subaru Select Monitor

Refer to “Read Diagnostic Trouble Code” for detailed operation procedure.

• General scan tool

For detailed operation procedures, refer to the general scan tool operation manual.

Is DTC displayed on Subaru Select Monitor or general scan tool?

Check DTC using “List of Diagnostic Trouble Code (DTC)”.

2.CHECK VEHICLE CONDITION.

Are properly-specified fuel filter, fuel hose, and fuel used?

Change the parts or fuel to properly-specified products.

3.CHECK FUEL DELIVERY LINE (HIGH PRESSURE LINE).

With the engine off, visually check the fuel delivery line (high pressure line).

Is there any leakage or trace of leakage on the fuel delivery line (high pressure line)?

Replace the faulty fuel delivery line.

4.CHECK ENGINE OIL AMOUNT.

Check the engine oil amount.

Does the engine oil amount increase significantly?

Check the fuel leaks into engine internal.

NOTE:

Using “Injector Control (Injection Stop Mode)”, identify the cylinder where fuel leaks is occurring to check intensively. In cylinder where the fuel leaks is occurring, the engine behavior change is small or does not change even when the injector is deactivated.

5.CHECK CURRENT DATA.

Read the data of “Common rail pressure” when the engine is off and cold, using the Subaru Select Monitor or a general scan tool.

NOTE:

• Subaru Select Monitor

For detailed operation procedures, refer to “READ CURRENT DATA FOR ENGINE”.

• General scan tool

For detailed operation procedures, refer to the general scan tool operation manual.

Is the data of “Common rail pressure” 15,000 kPa (112,528 mmHg, 4,430 inHg) or less?

6.CHECK COMMON RAIL PRESSURE SENSOR.

1) Turn the ignition switch to OFF.

2) Connect the CHECK BOARD to the ECM.

ST 18460AA010

CHECK BOARD

3) Turn the ignition switch to ON (engine OFF).

4) Measure the ECM connector terminal voltage using the CHECK BOARD.

Connector & terminal

(B134) No. 46 (+) — (B134) No. 76 (−):

Is the voltage 0.75 — 1.25 V?

Repair the poor contact of ECM connector.

Replace the common rail assembly.

7.CHECK COMMON RAIL PRESSURE.

Read the data of “Common rail pressure” following the common rail pressure inspection procedure when the engine is cold.

Is the data of “Common rail pressure” normal?

Replace the suction control valve. After replacing the part, go to the next step.

8.CHECK COMMON RAIL PRESSURE.

Read the data of “Common rail pressure” following the common rail pressure inspection procedure when the engine is warm.

Is the data of “Common rail pressure” normal?

9.CHECK COMMON RAIL PRESSURE.

Examine the check result in step 8 in detail.

Is the check result significantly below the lower limit of the Target Common Rail Pressure, with a waveform with cyclic down movements?

Replace the fuel pump.

• If the suction control valve has not been replaced in step 7: Replace the suction control valve.

• If the suction control valve has been replaced in step 7: Replace the fuel pump.

10.CHECK DTC.

Read DTC using Subaru Select Monitor or general scan tool.

NOTE:

• Subaru Select Monitor

Refer to “Read Diagnostic Trouble Code” for detailed operation procedure.

• General scan tool

For detailed operation procedures, refer to the general scan tool operation manual.

Is DTC displayed on Subaru Select Monitor or general scan tool?

• If the suction control valve has not been replaced in step 7: Replace the suction control valve.

• If the suction control valve has been replaced in step 7: Repair is complete.

11.CHECK REPLACEMENT HISTORY OF SUCTION CONTROL VALVE.

Has the suction control valve been replaced in step 7?

• If P0628, P0629, or P2635 was shown in step 10: Repair the poor contact of the suction control valve connector or coupling connector.

• If P0088, P0089, P1232, P1233, or P1234 was shown in step 10: Replace the fuel pump. After replacing the part, check DTC using “List of Diagnostic Trouble Code (DTC)”.

• If DTC other than the above was shown in step 10: Check DTC using “List of Diagnostic Trouble Code (DTC)”.

Check DTC using “List of Diagnostic Trouble Code (DTC)”.

1. COMMON RAIL PRESSURE INSPECTION PROCEDURE WHEN ENGINE IS COLD

CAUTION:

This inspection must be completed quickly before the engine coolant temperature reaches 60°C (140°F).

1. Turn off all the electric load.

2. In “Current Data Display & Save” on the Subaru Select Monitor, display the following items using the “data select display”.

Item	Unit
Coolant Temp.	°C or °F
Engine Speed	rpm
Common rail pressure	kPa, mmHg, inHg, or psig
Target Common Rail Pressure	kPa, mmHg, inHg, or psig

NOTE:

• If the “data select display” is not used, the measurement accuracy is degraded and correct measurement results cannot be obtained.

• Perform the measurement on the “digital data screen”.

• For detailed operation procedures, refer to “PC application help for Subaru Select Monitor”.

3. Start the engine when “Coolant Temp.” is less than 60°C (140°F), and measure each engine speed in Table 1 for approximately 10 seconds and save the measurement data.

If the “Common rail pressure” data at each engine speed is within the range shown in Table 1, it is normal.

NOTE:

• Perform the measurement quickly so that the “Coolant Temp.” does not become high.

• Examine the measurement data on the “Graph2 screen”. When doing so, change the range as necessary in order to examine the data in more detail.

• In Table 1, the actual “Target Common Rail Pressure” measurement value at each engine speed is shown as A, B, or C respectively.

Table 1 Common rail pressure change
Item	Engine speed
Item	Idling (Accelerator opening: 0%)	2,000 rpm (Accelerator opening: Constant)	4,000 rpm (Accelerator opening: Constant)
Common rail pressure (kPa)	A±3,000	B±3,000	C±3,000
Target Common Rail Pressure (kPa)	A	B	C

4. Start the engine when “Coolant Temp.” is less than 60°C (140°F), and measure each engine speed range in Table 2 three times consecutively and save the measurement data.

When the measurement is finished for all the engine speed ranges, repeat the measurement again and save the measurement data.

If the “Common rail pressure” data in each engine speed range is within the range shown in Table 2, it is normal.

NOTE:

• Perform the measurement quickly so that the “Coolant Temp.” does not become high.

• After keeping the accelerator pedal in the released state, bring the engine speed to the target speed with the accelerator opened to 100%. When the target speed is reached, release the accelerator pedal.

• Except when keeping the 2,000 rpm state, operate the accelerator pedal rapidly.

• Examine the measurement data on the “Graph2 screen”. When doing so, change the range as necessary in order to examine the data in more detail.

• In Table 2, the actual “Target Common Rail Pressure” measurement value in each engine speed range is shown as A, B, or C respectively.

Measurement image

Table 2 Common rail pressure following capacity
Item	Engine speed range
Item	Idling → 2,000 rpm (Accelerator opening: 0 → 100%)	Idling → 4,000 rpm (Accelerator opening: 0 → 100%)	2,000 → 4,000 rpm (Accelerator opening: Constant → 100%)
Common rail pressure (kPa)	≥ 20,000 and ≤ max. of A + 20,000 ≥ min. of A − 15,000	≥ 20,000 and ≤ max. of B + 20,000 ≥ min. of B − 15,000	≥ 20,000 and ≤ max. of C + 20,000 ≥ min. of C − 15,000
Target Common Rail Pressure (kPa)	A	B	C

2. COMMON RAIL PRESSURE INSPECTION PROCEDURE WHEN ENGINE IS WARM

1. Turn off all the electric load.

2. Perform the fuel pump compulsory learning mode.

3. In “Current Data Display & Save” on the Subaru Select Monitor, display the following items using the “data select display”.

Item	Unit
Coolant Temp.	°C or °F
Engine Speed	rpm
Common rail pressure	kPa, mmHg, inHg, or psig
Target Common Rail Pressure	kPa, mmHg, inHg, or psig

NOTE:

• If the “data select display” is not used, the measurement accuracy is degraded and correct measurement results cannot be obtained.

• Perform the measurement on the “digital data screen”.

• For detailed operation procedures, refer to “PC application help for Subaru Select Monitor”.

4. Measure each engine speed in Table 3 for approximately 10 seconds and save the measurement data.

If the “Common rail pressure” data at each engine speed is within the range shown in Table 3, it is normal.

NOTE:

• Examine the measurement data on the “Graph2 screen”. When doing so, change the range as necessary in order to examine the data in more detail.

• In Table 3, the actual “Target Common Rail Pressure” measurement value at each engine speed is shown as A, B, or C respectively.

Table 3 Common rail pressure change
Item	Engine speed
Item	Idling (Accelerator opening: 0%)	2,000 rpm (Accelerator opening: Constant)	4,000 rpm (Accelerator opening: Constant)
Common rail pressure (kPa)	A±3,000	B±3,000	C±3,000
Target Common Rail Pressure (kPa)	A	B	C

NOTE:

If the Common rail pressure is significantly below the lower limit of the Target Common Rail Pressure, with a waveform with cyclic down movements, the fuel pump needs to be replaced.

5. Measure each engine speed range in Table 4 three times consecutively and save the measurement data.

When the measurement is finished for all the engine speed ranges, repeat the measurement again and save the measurement data.

If the “Common rail pressure” data in each engine speed range is within the range shown in Table 4, it is normal.

NOTE:

• Except when keeping the 2,000 rpm state, operate the accelerator pedal rapidly.

• Examine the measurement data on the “Graph2 screen”. When doing so, change the range as necessary in order to examine the data in more detail.

• In Table 4, the actual “Target Common Rail Pressure” measurement value in each engine speed range is shown as A, B, or C respectively.

Measurement image

Table 4 Common rail pressure following capacity
Item	Engine speed range
Item	Idling → 2,000 rpm (Accelerator opening: 0 → 100%)	Idling → 4,000 rpm (Accelerator opening: 0 → 100%)	2,000 → 4,000 rpm (Accelerator opening: Constant → 100%)
Common rail pressure (kPa)	≥ 20,000 and ≤ max. of A + 20,000 ≥ min. of A − 15,000	≥ 20,000 and ≤ max. of B + 20,000 ≥ min. of B − 15,000	≥ 20,000 and ≤ max. of C + 20,000 ≥ min. of C − 15,000
Target Common Rail Pressure (kPa)	A	B	C