ENGINE (DIAGNOSTICS)(H4DOTC DIESEL) > Diagnostic Procedure with Diagnostic Trouble Code (DTC)

DTC P0304 CYLINDER 4 MISFIRE DETECTED

DTC DETECTING CONDITION:

Detected when two consecutive driving cycles with fault occur.

TROUBLE SYMPTOM:

• Improper idling

• Engine speed does not rise.

• Poor acceleration

CAUTION:

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

WIRING DIAGRAM:

STEPCHECKYESNO

1.CHECK FOR ANY OTHER DTC ON DISPLAY.

Are DTCs other than P0301, P0302, P0303 and P0304 displayed?

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

2.CHECK FUEL DELIVERY LINE.

Check fuel delivery line using Subaru Select Monitor.

WARNING:

When checking fuel delivery line during engine operation, be very careful so that one's hair, body and clothes do not touch the rotating part in the engine compartment.

NOTE:

For detailed procedures, refer to “High Pressure Fuel Inspection”.

Are there leaks from the fuel delivery line?

Replace the faulty fuel delivery line.

3.CHECK COMPRESSION PRESSURE.

Check the compression pressure of each cylinder.

NOTE:

For detailed procedures, refer to “Compression”.

Is the compression pressure normal?

Repair the faulty cylinder.

4.CHECK FUEL INJECTOR.

1) Turn the ignition switch to OFF.

2) Disconnect the connector from fuel injector on faulty cylinders.

3) Measure the resistance between fuel injector terminals.

Terminals

No. 1 — No. 2:

Is the resistance 0.2 — 1 Ω?

Even if DTC is detected, the circuit has returned to a normal condition at this time. Reproduce the failure, and then perform the diagnosis again.

NOTE:

In this case, temporary poor contact of connector may be the cause.

Replace the faulty fuel injector.