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Home >> Subaru >> 2006 >> Baja Turbo, Automatic >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 11 (Engine Controls - Engine (Diagnostics) (H4SO)) >> Diagnostic Procedure with Diagnostic Trouble Code (DTC) >> DTC P0304 - Cylinder 4 Misfire Detected -

DTC P0304 - Cylinder 4 Misfire Detected -

WARNING: This page is about a different variant/trim than selected.
DIAGNOSTIC PROCEDURE

Step Check Yes No
1 CHECK ANY OTHER DTC ON DISPLAY.  Is any other DTC displayed? Inspect the relevant DTC using "List of Diagnostic Trouble Code (DTC)". < Ref. to LIST OF DIAGNOSTIC TROUBLE CODE (DTC) . >
NOTE: In this case, it is not necessary to inspect DTC P0301, P0302, P0303 and P0304.
 Go to step 2. 
2 CHECK OUTPUT SIGNAL FROM ECM. 
  1. Turn ignition switch to ON.
  2. Measure voltage between ECM connector and chassis ground on malfunctioning cylinders.

    Connector & terminal 

    #1 (B134) No. 34 (+) - Chassis ground (-) 

    #2 (B134) No. 23 (+) - Chassis ground (-) 

    #3 (B134) No. 22 (+) - Chassis ground (-) 

    #4 (B134) No. 8 (+) - Chassis ground (-) 

 Is the measured value more than 10 V? Go to step 7.  Go to step 3. 
3 CHECK HARNESS BETWEEN FUEL INJECTOR AND ECM CONNECTOR. 
  1. Turn ignition switch to OFF.
  2. Disconnect connector from fuel injector on malfunctioning cylinders.
  3. Measure voltage between ECM connector and engine ground on malfunctioning cylinders.

    Connector & terminal 

    #1 (ES) No. 1 - Engine ground: 

    #2 (E16) No. 1 - Engine ground: 

    #3 (E6) No. 1 - Engine ground: 

    #4 (E17) No. 1 - Engine ground: 

 Is the measured value less than 10 Ω? Repair ground short circuit in harness between fuel injector and ECM connector. Go to step 4. 
4 CHECK HARNESS BETWEEN FUEL INJECTOR AND ECM CONNECTOR. 
Measure resistance of harness connector between ECM connector and fuel injector on malfunctioning cylinders.
Connector & terminal 
#1 (B134) No. 34 - (E5) No. 1: 
#2 (B134) No. 23 - (E16) No. 1: 
#3 (B134) No. 22 - (E6) No. 1: 
#4 (B134) No. 18 - (E17) No. 1: 		 Is the measured value less than 1 Ω? Go to step 5.  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
5 CHECK FUEL INJECTOR. 
Measure resistance between fuel injector terminals on malfunctioning cylinder.
Terminals 
No. 1 - No. 2: 		 Is the measured value within 5 to 20 Ω? Go to step 6.  Replace faulty fuel injector. < Ref. to FUEL INJECTOR . >
6 CHECK POWER SUPPLY LINE. 
  1. Turn ignition switch to ON.
  2. Measure voltage between fuel injector and engine ground on malfinctioning cylinders.

    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 (-): 

 Is the measured value more than 10 V? Repair poor contact in all connectors in fuel injector circuit. Repair harness and connector.
NOTE: In this case, repair the following:
  • Open circuit in harness between main relay and fuel injector connector on malfunctioning cylinders
  • Poor contact in coupling connector
  • Poor contact in main relay connector
  • Poor contact in fuel injector connector on malfunctioning cylinders
7 CHECK HARNESS BETWEEN FUEL INJECTOR AND ECM CONNECTOR. 
  1. Turn ignition switch to OFF.
  2. Disconnect connector from fuel injector on malfunctioning cylinder.
  3. Turn ignition switch to ON.
  4. Measure voltage between ECM connector and chassis ground on malfunctioning cylinders.

    Connector & terminal 

    #1 (B134) No. 34 (+) - Chassis ground (-) 

    #2 (B134) No. 23 (+) - Chassis ground (-) 

    #3 (B134) No. 22 (+) - Chassis ground (-) 

    #4 (B134) No. 8 (+) - Chassis ground (-) 

    Does the measured value exceed the specified value?

 Is the measured value more than 10 V? Repair battery short circuit in harness between ECM and fuel injector. After repair, replace ECM. < Ref. to ENGINE CONTROL MODULE . > Go to step 8. 
8 CHECK FUEL INJECTOR. 
  1. Turn ignition switch to OFF.
  2. Measure resistance between fuel injector terminals on malfunctioning cylinder.

    Terminals No. 1 - No. 2: 

 Is the measured value less than 1 Ω? Replace malfunctioning fuel injector < Ref. to FUEL INJECTOR > and ECM < Ref. to ENGINE CONTROL MODULE . > Go to step 9. 
9 CHECK INSTALLATION OF CAMSHAFT POSITION SENSOR/CRANKSHAFT POSITION SENSOR.  Is camshaft position sensor or crankshaft position sensor loosely installed? Tighten camshaft position sensor or crankshaft position sensor. Go to step 10  .
10 CHECK CRANKSHAFT SPROCKET. 
Remove timing belt cover.		 Is crankshaft sprocket rusted or does it have broken teeth? Replace crankshaft sprocket. < Ref. to CRANKSHAFT SPROCKET . > Go to step 11  .
11 CHECK INSTALLATION CONDITION OF TIMING BELT. 
Turn crankshaft using ST, and align alignment mark on crankshaft sprocket with alignment mark on cylinder block.		 Is timing belt dislocated from its proper position? Repair installation condition of timing belt. < Ref. to TIMING BELT . > Go to step 12  .
12 CHECK FUEL LEVEL.  Is the fuel meter indication higher than the "Lower" level? Go to step 13  . Replenish fuel so fuel meter indication is higher than the "Lower" level. After replenishing fuel, Go to step 13. 
13 CHECK STATUS OF CHECK ENGINE MALFUNCTION INDICATOR LAMP (MIL). 
  1. Clear memory using Subaru Select Monitor.

    < Ref. to CLEAR MEMORY MODE . >

  2. Start engine, and drive the vehicle more than 10 minutes.
 Is the MIL coming on or blinking? Go to step 15  . Go to step 14  .
14 CHECK CAUSE OF MISFIRE DIAGNOSED. 
NOTE: Disconnected spark plug code, etc.
 Was the cause of misfire diagnosed when the engine is running? Finish diagnostics operation, if the engine has no abnormality.
  1. 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 malfunctioning cylinders
    • Poor contact in ECM connector
    • Poor contact in coupling connector
  2. If there is no poor contact, contact SOA (distributor). Before contacting, the following items must be checked:
    • Fuel for condition
    • Fuel additives
    • Spark plug for condition
    • Plug code for condition
    • Engine oil for condition
15 CHECK AIR INTAKE SYSTEM.  Is there any malfunction in air intake system? Repair air intake system.
NOTE: Check the following items:
  • Are there air leaks or air suction caused by loose or dislocated nuts and bolts?
  • Are there cracks or any disconnection of hoses?
 Go to step 16  .
16 CHECK MISFIRE SYMPTOM. 
  1. Turn ignition switch to ON.
  2. Read diagnostic trouble code (DTC).

  • Subaru Select Monitor

    < Ref. to SUBARU SELECT MONITOR . >

  • General scan tool

    For detailed operation procedures, refer to the General Scan Tool Operation Manual.

NOTE: Perform diagnosis according to the items listed below.
 Does the Subaru Select Monitor or general scan tool indicate only one DTC? Go to step 21  . Go to step 17  .
17 CHECK DIAGNOSTIC TROUBLE CODE (DTC) ON DISPLAY.  Does the Subaru Select Monitor or general scan tool indicate DTC P0301 and P0302? Go to step 22  . Go to step 18  .
18 CHECK DIAGNOSTIC TROUBLE CODE (DTC) ON DISPLAY.  Does the Subaru Select Monitor or general scan tool indicate DTC P0303 and P0304? Go to step 23  . Go to step 19  .
19 CHECK DIAGNOSTIC TROUBLE CODE (DTC) ON DISPLAY.  Does the Subaru Select Monitor or general scan tool indicate DTC P0301 and P0303? Go to step 24  . Go to step 20  .
20 CHECK DIAGNOSTIC TROUBLE CODE (DTC) ON DISPLAY.  Does the Subaru Select Monitor or general scan tool indicate DTC P0302 and P0304? Go to step 25  . Go to step 26  .
21 ONLY ONE CYLINDER  Is there any malfunction in that cylinder? Repair or replace malfunctioning parts.
NOTE: Check the following items.
  • Spark plug
  • Spark plug cord
  • Fuel injector
  • Compression ratio
 Go to DTC P0171. < Ref. to DTC P0171 - SYSTEM TOO LEAN (BANK 1) - , Diagnostic Procedure with Diagnostic Trouble Code (DTC). >
22 GROUP OF #1 AND #2 CYLINDERS  Are there malfunctions in #1 and #2 cylinders? Repair or replace malfunctioning parts.
NOTE:
  • Check the following items.
    • Spark plugs
    • Fuel injectors
    • Ignition coil
    • Compression ratio
  • If no abnormal is discovered, check for "IGNITION CONTROL SYSTEM" of #1 and #2 cylinders side. < Ref. to IGNITION CONTROL SYSTEM , Diagnostics for Engine Starting Failure. >
 Go to DTC P0171. < Ref. to DTC P0171 - SYSTEM TOO LEAN (BANK 1) - , Diagnostic Procedure with Diagnostic Trouble Code (DTC). >
23 GROUP OF #3 AND #4 CYLINDERS  Are there malfunctions in #3 and #4 cylinders? Repair or replace malfunctioning parts.
NOTE:
  • Check the following items.
    • Spark plugs
    • Fuel injectors
    • Ignition coil
  • If no abnormal is discovered, check for "16. D: IGNITION CONTROL SYSTEM" of #3 and #4 cylinders side. < Ref. to IGNITION CONTROL SYSTEM , Diagnostics for Engine Starting Failure. >
 Go to DTC P0171. < Ref. to DTC P0171 - SYSTEM TOO LEAN (BANK 1) - , Diagnostic Procedure with Diagnostic Trouble Code (DTC). >
24 GROUP OF #1 AND #3 CYLINDERS  Are there malfunctions in #1 and #3 cylinders? Repair or replace malfunctioning parts.
NOTE: Check the following items.
  • Spark plugs
  • Fuel injectors
  • Skipping timing belt teeth
 Go to DTC P0171. < Ref. to DTC P0171 - SYSTEM TOO LEAN (BANK 1) - , Diagnostic Procedure with Diagnostic Trouble Code (DTC). >
25 GROUP OF #2 AND #4 CYLINDERS  Are there malfunctions in #2 and #4 cylinders? Repair or replace malfunctioning parts.
NOTE: Check the following items.
  • Sparkplugs
  • Fuel injectors
  • Compression ratio
  • Skipping timing belt teeth
 Go to DTC P0171. < Ref. to DTC P0171 - SYSTEM TOO LEAN (BANK 1) - , Diagnostic Procedure with Diagnostic Trouble Code (DTC). >
26 CYLINDER AT RANDOM  Is the engine idle unstable? Go to DTC P0171. < Ref. to DTC P0171 - SYSTEM TOO LEAN (BANK 1) - , Diagnostic Procedure with Diagnostic Trouble Code (DTC). > Repair or replace malfunctioning parts.
NOTE: Check the following items.
  • Sparkplugs
  • Fuel injectors
  • Compression ratio

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