P0304
AA: DTC P0304 - CYLINDER 4 MISFIRE DETECTEDDTC DETECTING CONDITION:
- Two consecutive driving cycles with fault.
- Immediately at fault recognition (A misfire which could damage catalyst occurs.)
TROUBLE SYMPTOM:
- Engine stalls.
- Erroneous idling
- Rough driving
CAUTION: After repair or replacement of faulty parts, conduct CLEAR MEMORY MODE and INSPECTION MODE. Refer to How To Clear Diagnostic Trouble Codes. Clearing Diagnostic Trouble Codes
WIRING DIAGRAM
10AA1: CHECK ANY OTHER DTC ON DISPLAY.
CHECK: Does the Subaru Select Monitor or OBD-II general scan tool indicate DTC P0101, P0102, P0103, P0116, P0117 or P0125?
YES: Inspect DTC P0101, P0102, P0103, P0116, P0117 or P0125 using "10. Diagnostics Chart with Trouble Code". P0101 P0102 P0103 P0116 P0117 P0125
NOTE: In this case, it is not necessary to inspect DTC P0301, P0302, P0303 and P0304.
NO: Go to step 10AA2.
10AA2: CHECK OUTPUT SIGNAL FROM ECM.
1. Turn ignition switch to ON.
Connector & Terminal#1 (B134) No.4 (+) - Chassis ground (-): #2 (B134) No.13 (+) - Chassis ground (-): #3 (B134) No.14 (+) - Chassis ground (-): #4 (B134) No.15 (+) - Chassis ground (-)::
2. Measure voltage between ECM connector and chassis ground on faulty cylinders.
CHECK: Is the voltage more than 10 V?
YES: Go to step 10AA7.
NO: Go to step 10AA3.
10AA3: CHECK HARNESS BETWEEN FUEL INJECTOR AND ECM CONNECTOR.
1. Turn ignition switch to OFF
2. Disconnect connector from fuel injector on faulty cylinders.
Connector & Terminal#1 (E5) No.1 - Engine ground:#2 (E16) No.1 - Engine ground:#3 (E6) No.1 - Engine ground:#4 (E17) No.1 - Engine ground::
3. Measure voltage between ECM connector and engine ground on faulty cylinders.
CHECK: Is the resistance less than 10 ohms?
YES: Repair ground short circuit in harness between fuel injector and ECM connector.
NO: Go to step 10AA4.
10AA4: CHECK HARNESS BETWEEN FUEL INJECTOR AND ECM CONNECTOR.
Connector & Terminal #1 (B134) No.4 - (E5) No.1: #2 (B134) No.13 - (E16) No.1: #3 (B134) No.14 - (E6) No.1: #4 (B134) No. 15 - (E17) No.1::
Measure resistance of harness connector between ECM connector and fuel injector on faulty cylinders.
CHECK: Is the resistance less than 1 ohm?
YES: Go to step 10AA5.
NO: Repair harness and connector.
NOTE:
In this case, repair the following:
- Open circuit in harness between ECM and fuel injector connector
- Poor contact in coupling connector (B21)
10AA5: CHECK FUEL INJECTOR.
Terminals No.1 - No.2:
Measure resistance between fuel injector terminals on faulty cylinder.
CHECK: Is the resistance between 5 and 20 ohms?
YES: Go to step 10AA6.
NO: Replace faulty fuel injector.
10AA6: CHECK POWER SUPPLY LINE.
1. Turn ignition switch to ON.
Connector & Terminal#1 (E5) No.2 (+) - Engine ground (-):#2 (E16) No.2 (+) - Engine ground (-):#3 (E6) No.2 (+) - Engine ground (-):#4 (E17) No.2 (+) - Engine ground (-)::
2. Measure voltage between fuel injector and engine ground on faulty cylinders.
CHECK: Is the voltage more than 10 V?
YES: Repair poor contact in all connectors in fuel injector circuit.
NO: Repair harness and connector.
NOTE:
In this case, repair the following:
- Open circuit in harness between main relay and fuel injector connector on faulty cylinders.
- Poor contact in coupling connector (B21).
- Poor contact in main relay connector.
- Poor contact in fuel injector connector on faulty cylinders.
10AA7: CHECK HARNESS BETWEEN FUEL INJECTOR AND ECM CONNECTOR.
1. Turn ignition switch to OFF.
2. Disconnect connector from fuel injector on faulty cylinder.
3. Turn ignition switch to ON.
Connector & Terminal#1 (B134) No.4 (+) - Chassis ground (-):#2 (B134) No.13 (+) - Chassis ground (-):#3 (B134) No.14 (+) - Chassis ground (-):#4 (B134) No.15 (+) - Chassis ground (-)::
4. Measure voltage between ECM connector and chassis ground on faulty cylinders.
CHECK: Is the voltage more than 10 V?
YES: Repair battery short circuit in harness between ECM and fuel injector. After repair, replace ECM.
NO: Go to step 10AA8.
10AA8: CHECK FUEL INJECTOR.
1. Turn ignition switch to OFF.
Terminals No.1 - No.2:
2. Measure resistance between fuel injector terminals on faulty cylinder.
CHECK: Is the resistance less than 1 ohm?
YES: Replace faulty fuel injector and ECM.
NO: Go to step 10AA9.
1OAA9: CHECK FUEL LEVEL.
CHECK: Is fuel meter indication (in combination meter) higher than the "Lower" level?
YES: Go to step 10AA10.
NO: Replenish fuel so fuel meter indication is higher than the "Lower" level. After refuel, Go to step 10AA10.
10AA10: CHECK STATUS OF CHECK ENGINE MALFUNCTION INDICATOR LAMP (MIL).
1) Turn ignition switch to OFF
2) Connect Subaru Select Monitor to the data link connector.
3) Clear memory using Subaru Select Monitor.
4) Start engine, and drive the vehicle more than 10 minutes.
CHECK: Is the MIL coming on or blinking?
YES: Go to step 10AA12.
NO: Go to step 10AA11.
10AA11: CHECK CAUSE OF MISFIRE DIAGNOSED.
CHECK: Was the cause of misfire diagnosed when the engine is running?
YES: Finish diagnostics operation, if the engine has no abnormality.
NOTE:
Ex. Remove spark plug cord, etc.
NO: Repair poor contact.
NOTE:
In this case, repair the following:
- Poor contact in ignitor connector
- Poor contact in ignition coil connector
- Poor contact in fuel injector connector on faulty cylinders
- Poor contact in ECM connector
- Poor contact in coupling connector (B21)
10AA12: CHECK AIR INTAKE SYSTEM.
CHECK: Is there a fault in air intake system?
YES: Repair air intake system.
NOTE:
Check the following items:
- Are there air leaks or air suction caused by loose or dislocated nuts and bolt.?
- Are there cracks or any disconnection of hoses?
NO: Go to step 10AA13.
10AA13: CHECK MISFIRE SYMPTOM.
1) Turn ignition switch to OFF.
2) Connect the Subaru Select Monitor or the OBD-II general scan tool to data link connector.
3) Turn ignition switch to ON, and turn Subaru Select Monitor or 080-II general scan tool switch to ON.
4) Read diagnostic trouble code (DTC).
- Subaru Select Monitor
- OBD-II general scan tool
For detailed operation procedures, refer to the OBD-II General Scan Tool Operation Manual.
NOTE:
Perform diagnosis according to the items listed below.
CHECK: Does the Subaru Select Monitor or OBD II general scan tool indicate only one DTC?
YES: Go to step 10AA18.
NO: Go to step 10AA14.
10AA14: CHECK DIAGNOSTIC TROUBLE CODE (DTC) ON DISPLAY.
CHECK: Does the Subaru Select Monitor or OBD II general scan tool indicate DTC P0301 and P0302?
YES: Go to step 10AA19.
NO: Go to step 10AA15.
10AA15: CHECK DIAGNOSTIC TROUBLE CODE (DTC) ON DISPLAY.
CHECK: Does the Subaru Select Monitor or OBD II general scan tool indicate DTC P0303 and P0304?
YES: Go to step 10AA20.
NO: Go to step 10AA16.
10AA16: CHECK DIAGNOSTIC TROUBLE CODE (DTC) ON DISPLAY.
CHECK: Does the Subaru Select Monitor or OBD-II general scan tool indicate DTC P0301 and P0303?
YES: Go to step 10AA21.
NO: Go to step 10AA17.
10AA17: CHECK DIAGNOSTIC TROUBLE CODE (DTC) ON DISPLAY.
CHECK: Does the Subaru Select Monitor or OBD II general scan tool indicate DTC P0302 and P0304?
YES: Go to step 10AA22.
NO: Go to step 10AA18.
10AA18: ONLY ONE CYLINDER
CHECK: Is there a fault in that cylinder?
YES: Repair or replace faulty parts.
NOTE:
Check the following items.
- Spark plug
- Spark plug cord
- Fuel injector
- Compression ratio
NO: Go to DTC P0170. P0170
10AA19: GROUP OF #1 AND #2 CYLINDERS
CHECK: Are there faults in #1 and #2 cylinders?
YES: Repair or replace faulty parts.
NOTE:
- Check the following items.
- Spark plugs
- Fuel injectors
- Ignition coil
- Compression ratio
- If no abnormal is discovered, check for "8. D: IGNITION CONTROL SYSTEM" of #1 and #2 cylinders side.
NO: Go to DTC P0170. P0170
10AA20: GROUP OF #3 AND #4 CYLINDERS
CHECK: Are there faults in #3 and #4 cylinders?
YES: Repair or replace faulty parts.
NOTE:
- Check the following items.
- Spark plugs
- Fuel injectors
- Ignition coil
- If no abnormal is discovered, check for "8. D: IGNITION CONTROL SYSTEM" of #3 and #4 cylinders side.
NO: Go to DTC P0170. P0170
10AA21: GROUP OF #1 AND #3 CYLINDERS
CHECK: Are there faults in #1 and #3 cylinders?
YES: Repair or replace faulty parts.
NOTE:
Check the following items.
- Spark plugs
- Fuel injectors
- Skipping timing belt teeth
NO: Go to DTC P0170. P0170
10AA22: GROUP OF #2 AND #4 CYLINDERS
CHECK: Are there faults in #2 and #4 cylinders?
YES: Repair or replace faulty parts.
NOTE:
Check the following items.
- Spark plugs
- Fuel injectors
- Compression ratio
- Skipping timing belt teeth
NO: Go to DTC P0170. P0170
10AA23: CYLINDER AT RANDOM
CHECK: Is the engine idle rough?
YES: Go to DTC P0170. P0170
NO: Repair or replace faulty parts.
NOTE:
Check the following items.
- Spark plugs
- Fuel injectors
- Compression ratio