3Ur-Fe Engine Control. Dtc P0300 Random / Multiple Cylinder Misfire Detected

When the engine misfires, high concentrations of hydrocarbons (HC) enter the exhaust gas. Extremely high HC concentration levels can cause increases in exhaust emission levels. High concentrations of HC can also cause increases in the Three-Way Catalytic Converter (TWC) temperature, which may cause damage to the TWC. To prevent these increases in emissions and to limit the possibility of thermal damage, the ECM monitors the misfire rate. When the temperature of the TWC reaches the point of thermal degradation, the MIL blinks. To monitor misfires, the ECM uses both the Camshaft Position (CMP) sensor and the Crankshaft Position (CKP) sensor. The CMP sensor is used to identify any misfiring cylinders and the CKP sensor is used to measure variations in the crankshaft rotation speed. Misfires are counted as when the crankshaft rotation speed variations exceed predetermined thresholds.
If the misfire rate exceeds the threshold level, the ECM stores DTC(s).

DTC Code	DTC Detection Condition	Trouble Area
P0300	Simultaneous misfiring of several cylinders occurs and one of the following conditions below is detected (2 trip detection logic): A high temperature misfire occurs in the Three-Way Catalytic Converter (TWC). An emission deterioration misfire occurs.	Open or short in engine wire harness Connector connection Vacuum hose connections Ignition system Fuel injector Fuel pressure Mass Air Flow (MAF) meter Engine Coolant Temperature (ECT) sensor Compression pressure Valve timing PCV valve and hose PCV hose connections Air induction system ECM
P0301 P0302 P0303 P0304 P0305 P0306 P0307 P0308	Misfiring of a specific cylinder occurs and one of the following conditions below is detected (2 trip detection logic): A high temperature misfire occurs in the Three-Way Catalytic Converter (TWC). An emission deterioration misfire occurs.

HINT:

When multiple DTCs for misfiring cylinders are stored, but DTC P0300 is not stored, it indicates that misfires have been detected in different cylinders at different times. DTC P0300 is only stored when several misfiring cylinders are detected at the same time.

MONITOR DESCRIPTION

The ECM stores a DTC when either one of the following conditions, which could cause emission deterioration, is detected (2 trip detection logic).

Within the first 1000 crankshaft revolutions of the engine starting, an excessive misfiring rate (approximately 30 to 110 misfires per 1000 crankshaft revolutions) occurs once.
An excessive misfiring rate (approximately 30 to 110 misfires per 1000 crankshaft revolutions) occurs a total of 4 times.

The ECM flashes the MIL (immediate detection logic) and stores a DTC (2 trip detection logic) when either one of the following conditions, which could cause the Three-Way Catalytic Converter (TWC) damage, is detected.

At a high engine speed, a catalyst damage misfire, which monitored every 200 crankshaft revolutions, occurs once.
At a normal engine speed, a catalyst damage misfire, which monitored every 200 crankshaft revolutions, occurs 3 times.

WIRING DIAGRAM

Refer to DTC P0351 (Click here).
Refer to Fuel Injector Circuit (Click here).

CONFIRMATION DRIVING PATTERN

Connect the intelligent tester to the DLC3.
Turn the engine switch on (IG).
Turn the tester on.
Record the DTC(s) and freeze frame data.
Using the tester, switch the ECM from normal mode to check mode (Click here).
Read the misfire counts of each cylinder (cylinder No. 1 to No. 8) with the engine in an idling condition. If any misfire count is displayed, skip the following confirmation driving pattern.
Drive the vehicle several times with the conditions, such as engine speed and engine load, shown in Misfire RPM and Misfire Load in the Data List.

HINT:
In order to store misfire DTCs, it is necessary to operate the vehicle for the period of time shown in the table below, with the Misfire RPM and Misfire Load in the Data List.

Engine Speed
Duration
Idling
8 minutes or more
1000
4.5 minutes or more
2000
2.5 minutes or more
3000
1.5 minute or more
Check whether misfires have occurred by checking DTCs and freeze frame data.
HINT:
Do not turn the engine switch off until the stored DTC(s) and freeze frame data have been recorded. When the ECM returns to normal mode (default), the stored DTC(s), freeze frame data and other data will be cleared.
Record the DTC(s), freeze frame data and misfire counts.
Turn the engine switch off and wait for at least 5 seconds.

INSPECTION PROCEDURE

HINT:

DTC P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307 and P0308 are for Euro-OBD only.
If any DTCs other than misfire DTCs are output, troubleshoot those DTCs first.
Read freeze frame data using the intelligent tester. Freeze frame data records the engine condition when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data from the time the malfunction occurred.
If the misfire does not recur when the vehicle is brought to the workshop, reproduce the conditions stored in the freeze frame data.
If the misfire still cannot be reproduced even though the conditions stored in the freeze frame data have been duplicated, one of the following factors is considered to be a possible cause of the problem:

The fuel level is low.
Improper fuel is used.
The spark plugs are dirty.

After finishing repairs, check that no misfires occur in each cylinder (cylinder No. 1, No. 2, No. 3, No. 4, No. 5, No. 6, No. 7 and No. 8).
Be sure to confirm that no misfiring cylinder DTCs are output again by conducting the confirmation driving pattern after the repairs.
For 6 and 8 cylinder engines, the ECM intentionally does not store the specific misfiring cylinder DTCs at high engine speed. If misfires only occur during high engine speed driving, only DTC P0300 is stored.
In the event of DTC P0300 being present, perform the following operations:

Clear the DTC (Click here).
Start the engine and conduct the confirmation driving pattern.
Read the misfiring rates of each cylinder or DTC(s) using the intelligent tester.
Repair the cylinder(s) that has a high misfiring rate or is indicated by the DTC.
After finishing repairs, conduct the confirmation driving pattern again, in order to verify that DTC P0300 is not output.

When either Short FT #1, Long FT #1, Short FT #2 or Long FT #2 in the freeze frame data is outside the range of +/-20%, the air-fuel ratio may be rich (-20% or less) or lean (+20% or more).
When the Coolant Temp in the freeze frame data is below 75°C (167°F), the misfires occurred only while warming up the engine.
An extremely imbalanced drive wheel which causes body vibration may cause misfire DTCs to be detected.

1.CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO MISFIRE CODES)

Connect the intelligent tester to the DLC3.

Turn the engine switch on (IG).

Turn the tester on.

Enter the following menus: Powertrain / Engine and ECT / DTC.

Read DTCs.

Result
Result
Proceed to
P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307 and/or P0308 are output
A
P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307 and/or P0308 and other DTCs are output
B

Result
Result	Proceed to
P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307 and/or P0308 are output	A
P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307 and/or P0308 and other DTCs are output	B

HINT:

If any DTCs other than P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307 and P0308 are output, troubleshoot those DTCs first.

GO TO DTC CHART (Click here)

A

2.CHECK PCV HOSE CONNECTIONS

Check the PCV hose connections.
OK:
PCV hose is connected correctly and is not damaged.

REPAIR OR REPLACE PCV HOSE (Click here)

OK

3.READ VALUE USING INTELLIGENT TESTER (MISFIRE RPM AND MISFIRE LOAD)

Connect the intelligent tester to the DLC3.

Turn the engine switch on (IG) and turn the tester on.

Enter the following menus: Powertrain / Engine and ECT / Data List / Misfire / Misfire RPM and Misfire Load.

Read and note the Misfire RPM and Misfire Load values.
HINT:
The Misfire RPM and Misfire Load values indicate the vehicle conditions under which the misfire occurred.

NEXT

4.READ VALUE USING INTELLIGENT TESTER (MISFIRE COUNT)

Connect the intelligent tester to the DLC3.

Turn the engine switch on (IG).

Turn the tester on.

Clear DTCs (Click here).

Enter the following menus: Powertrain / Engine and ECT / Data List / Misfire / Cylinder #1 Misfire Count, #2, #3, #4, #5, #6, #7 and #8.

Allow the engine to idle.

Read each value for Cylinder #1 Misfire Count to #8 displayed on the tester. If no misfire counts occur in any cylinders, perform the following procedures:
1. Move the shift lever to D.
2. Check the Cylinder #1 Misfire Count to #8.
3. If misfire counts are still not displayed, perform procedure "A" and "B" and then check the misfire counts again.

Drive the vehicle with the Misfire RPM and Misfire Load noted in the "Read Value Using tester (Misfire RPM and Misfire Load)" procedures above (Procedure "A").

Read the Cylinder #1 Misfire Count to #8 or DTCs displayed on the tester (Procedure "B").

Result
Misfire Count
Proceed to
Most misfires occur in only 1 or 2 cylinders
A
3 cylinders or more have equal misfire counts
B
HINT:
1. If it is difficult to reproduce misfires for each cylinder, check the Data List item called Misfire Margin. Try to find vehicle driving conditions that lower the Misfire Margin value. Values above 30% are considered normal.
2. If the freeze frame data record of the ECT is below 75°C (167°F), the misfire may be detected only when the engine is cold.
3. If the freeze frame data record of the Engine Run Time is below 120 seconds, the misfire may be detected immediately after the engine is started.

Result
Misfire Count	Proceed to
Most misfires occur in only 1 or 2 cylinders	A
3 cylinders or more have equal misfire counts	B

Go to step 16

A

5.INSPECT SPARK PLUG

Inspect the spark plug of the misfiring cylinder (Click here).

REPLACE SPARK PLUG (Click here)

OK

6.CHECK FOR SPARKS AND IGNITION

Disconnect the injector connectors to prevent the engine from starting.
CAUTION:
Always disconnect all injector connectors.
NOTICE:
Do not crank the engine for more than 2 seconds.

Remove the ignition coil from the cylinder head (Click here).

Install the spark plug onto the ignition coil.

Attach the spark plug assembly to the cylinder head.

Crank the engine for less than 2 seconds and check the spark.
OK:
Sparks jump across electrode gap.

Install the ignition coil.

Reconnect the injector connectors.

Go to step 32

OK

7.CHECK CYLINDER COMPRESSION PRESSURE

Measure the cylinder compression pressure of the misfiring cylinder (Click here).

CHECK ENGINE TO DETERMINE CAUSE OF LOW COMPRESSION

OK

8.CHECK FUEL INJECTOR OF MISFIRING CYLINDER

Check the injector injection [whether fuel volume is high or low, and whether injection pattern is poor] (Click here).

GO TO FUEL INJECTOR CIRCUIT (Click here)

OK

9.CHECK HARNESS AND CONNECTOR

Disconnect the fuel injector connector.

Disconnect the C45 ECM connector.

Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Cylinder	Tester Connection	Condition	Specified Condition
No. 1	a5-1 - Body ground	Always	10 kΩ or higher
No. 1	a5-1 - C45-86 (#10)	Always	Below 1 Ω
No. 2	a1-1 - Body ground	Always	10 kΩ or higher
No. 2	a1-1 - C45-109 (#20)	Always	Below 1 Ω
No. 3	a6-1 - Body ground	Always	10 kΩ or higher
No. 3	a6-1 - C45-85 (#30)	Always	Below 1 Ω
No. 4	a2-1 - Body ground	Always	10 kΩ or higher
No. 4	a2-1 - C45-108 (#40)	Always	Below 1 Ω
No. 5	a7-1 - Body ground	Always	10 kΩ or higher
No. 5	a7-1 - C45-84 (#50)	Always	Below 1 Ω
No. 6	a3-1 - Body ground	Always	10 kΩ or higher
No. 6	a3-1 - C45-107 (#60)	Always	Below 1 Ω
No. 7	a8-1 - Body ground	Always	10 kΩ or higher
No. 7	a8-1 - C45-83 (#70)	Always	Below 1 Ω
No. 8	a4-1 - Body ground	Always	10 kΩ or higher
No. 8	a4-1 - C45-106 (#80)	Always	Below 1 Ω

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

10.CHECK FUEL INJECTOR OF MISFIRING CYLINDER

Check the injector injection [whether fuel volume is high or low, and whether injection pattern is poor] (Click here).

REPLACE FUEL INJECTOR ASSEMBLY (Click here)

OK

11.CHECK AIR INDUCTION SYSTEM

Check the air induction system for vacuum leakage (Click here).
OK:
No leakage from air induction system.

REPAIR OR REPLACE AIR INDUCTION SYSTEM (Click here)

OK

12.CHECK FUEL PRESSURE

Check the fuel pressure (Click here).

Go to step 34

OK

13.READ VALUE USING INTELLIGENT TESTER (COOLANT TEMP)

Connect the intelligent tester to the DLC3.

Turn the engine switch on (IG).

Turn the tester on.

Enter the following menus: Powertrain / Engine and ECT / Data List / All Data / Coolant Temp.

Read the Coolant Temp twice, when the engine is both cold and warmed up.
Standard:
With cold engine:
Same as ambient air temperature.
With warm engine:
Between 75°C and 100°C (167°F and 212°F).

REPLACE ENGINE COOLANT TEMPERATURE SENSOR (Click here)

OK

14.INSPECT MASS AIR FLOW METER

Connect the intelligent tester to the DLC3.

Turn the engine switch on (IG).

Turn the tester on.

Enter the following menus: Powertrain / Engine and ECT / Data List / All Data / MAF and Coolant Temp.

Allow the engine to idle until Coolant Temp reaches 75°C (167°F) or higher.

Read MAF with the engine speed at 3000 rpm.
Standard:
Between 25.2 gm/s and 35.2 gm/s (shift lever: N; A/C: Off).

Go to step 27

OK

15.CHECK VALVE TIMING

Remove the cylinder head cover LH and RH.

Turn the crankshaft pulley, and align its groove with the timing mark "0" of the timing chain cover.

Check that the timing marks of the camshaft timing gears and camshaft timing exhaust gears are at the positions shown in the illustration.
OK:
Timing marks on camshaft timing gears are aligned as shown in the illustration.

Go to step 27

ADJUST VALVE TIMING (Click here)

16.CHECK AIR INDUCTION SYSTEM

Check the air induction system for vacuum leakage (Click here).
OK:
No leakage from air induction system.

REPAIR OR REPLACE AIR INDUCTION SYSTEM (Click here)

OK

17.CHECK FUEL PRESSURE

Check the fuel pressure (Click here).

Go to step 34

OK

18.READ VALUE USING INTELLIGENT TESTER (COOLANT TEMP)

Connect the intelligent tester to the DLC3.

Turn the engine switch on (IG) and turn the tester on.

Enter the following menus: Powertrain / Engine and ECT / Data List / All Data / Coolant Temp.

Read the Coolant Temp twice, when the engine is both cold and warmed up.
Standard:
With cold engine:
Same as ambient air temperature.
With warm engine:
Between 75°C and 100°C (167°F and 212°F).

REPLACE ENGINE COOLANT TEMPERATURE SENSOR (Click here)

OK

19.INSPECT MASS AIR FLOW METER

Connect the intelligent tester to the DLC3.

Turn the engine switch on (IG).

Turn the tester on.

Enter the following menus: Powertrain / Engine and ECT / Data List / All Data / MAF and Coolant Temp.

Allow the engine to idle until Coolant Temp reaches 75°C (167°F) or higher.

Read MAF with the engine speed at 3000 rpm.
Standard:
Between 25.2 gm/s and 35.2 gm/s (shift lever: N; A/C: Off).

Go to step 27

OK

20.CHECK VALVE TIMING

Remove the cylinder head cover LH and RH.

Turn the crankshaft pulley, and align its groove with the timing mark "0" of the timing chain cover.

Check that the timing marks of the camshaft timing gears and camshaft timing exhaust gears are at the positions shown in the illustration.
OK:
Timing marks on camshaft timing gears are aligned as shown in the illustration.

ADJUST VALVE TIMING (Click here)

OK

21.INSPECT SPARK PLUG

Inspect the spark plug of the misfiring cylinder (Click here).

REPLACE SPARK PLUG (Click here)

OK

22.CHECK FOR SPARKS AND IGNITION

Disconnect the injector connectors to prevent the engine from starting.
CAUTION:
Always disconnect all injector connectors.
NOTICE:
Do not crank the engine for more than 2 seconds.

Remove the ignition coil from the cylinder head (Click here).

Install the spark plug onto the ignition coil.

Attach the spark plug assembly to the cylinder head.

Crank the engine for less than 2 seconds and check the spark.
OK:
Sparks jump across electrode gap.

Install the ignition coil.

Reconnect the injector connectors.

Go to step 32

OK

23.CHECK CYLINDER COMPRESSION PRESSURE

Measure the cylinder compression pressure of the misfiring cylinder (Click here).

CHECK ENGINE TO DETERMINE CAUSE OF LOW COMPRESSION

OK

24.CHECK FUEL INJECTOR ASSEMBLY (POWER SOURCE)

Disconnect the fuel injector connector.

Measure the voltage according to the value(s) in the table below.

Standard Voltage:

Cylinder	Tester Connection	Switch Condition	Specified Condition
No. 1	a5-2 - Body ground	Engine switch on (IG)	11 to 14 V
No. 2	a1-2 - Body ground	Engine switch on (IG)	11 to 14 V
No. 3	a6-2 - Body ground	Engine switch on (IG)	11 to 14 V
No. 4	a2-2 - Body ground	Engine switch on (IG)	11 to 14 V
No. 5	a7-2 - Body ground	Engine switch on (IG)	11 to 14 V
No. 6	a3-2 - Body ground	Engine switch on (IG)	11 to 14 V
No. 7	a8-2 - Body ground	Engine switch on (IG)	11 to 14 V
No. 8	a4-2 - Body ground	Engine switch on (IG)	11 to 14 V

GO TO FUEL INJECTOR CIRCUIT (Click here)

OK

25.CHECK HARNESS AND CONNECTOR (FUEL INJECTOR - ECM)

Disconnect the fuel injector connector.

Disconnect the C45 ECM connector.

Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Cylinder	Tester Connection	Condition	Specified Condition
No. 1	a5-1 - Body ground	Always	10 kΩ or higher
No. 1	a5-1 - C45-86 (#10)	Always	Below 1 Ω
No. 2	a1-1 - Body ground	Always	10 kΩ or higher
No. 2	a1-1 - C45-109 (#20)	Always	Below 1 Ω
No. 3	a6-1 - Body ground	Always	10 kΩ or higher
No. 3	a6-1 - C45-85 (#30)	Always	Below 1 Ω
No. 4	a2-1 - Body ground	Always	10 kΩ or higher
No. 4	a2-1 - C45-108 (#40)	Always	Below 1 Ω
No. 5	a7-1 - Body ground	Always	10 kΩ or higher
No. 5	a7-1 - C45-84 (#50)	Always	Below 1 Ω
No. 6	a3-1 - Body ground	Always	10 kΩ or higher
No. 6	a3-1 - C45-107 (#60)	Always	Below 1 Ω
No. 7	a8-1 - Body ground	Always	10 kΩ or higher
No. 7	a8-1 - C45-83 (#70)	Always	Below 1 Ω
No. 8	a4-1 - Body ground	Always	10 kΩ or higher
No. 8	a4-1 - C45-106 (#80)	Always	Below 1 Ω

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

26.CHECK FUEL INJECTOR ASSEMBLY OF MISFIRING CYLINDER

Check the fuel injector injection [whether fuel volume is high or low, and whether injection pattern is poor] (Click here).

REPLACE FUEL INJECTOR ASSEMBLY (Click here)

OK

27.CHECK HARNESS AND CONNECTOR

Check the connection and terminal contact pressure of connectors and wire harnesses between the mass air flow meter and ECM (Click here).
HINT:
Repair any problems.

NEXT

28.CHECK WHETHER DTC OUTPUT RECURS

Connect the intelligent tester to the DLC3.

Turn the engine switch on (IG).

Turn the tester on.

Clear the DTCs (Click here).

Turn the engine switch off.

Turn the engine switch on (IG) and turn the tester on.

Start the engine and warm it up.

Drive the vehicle in accordance with the driving pattern described in Confirmation Driving Pattern.

Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.

Input the DTC: P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307 or P0308.

Check the DTC judgment result.

Result
Display (DTC Output)
Proceed to
ABNORMAL
(P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307 or P0308 output)
A
NORMAL
(No DTC output)
B

END

A

29.CHECK HARNESS AND CONNECTOR (MASS AIR FLOW METER - ECM)

Disconnect the mass air flow meter connector.

Disconnect the ECM connector.

Measure the resistance according to the value(s) in the table below.

Standard Resistance:

Tester Connection
Condition
Specified Condition
C50-3 (VG) - C45-68 (VG)
Always
Below 1 Ω
C50-2 (E2G) - C45-70 (E2G)
Always
Below 1 Ω
C50-3 (VG) or C45-68 (VG) - Body ground
Always
10 kΩ or higher

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

30.REPLACE MASS AIR FLOW METER

Replace the mass air flow meter assembly (Click here).

HINT:

If the results of the inspections performed in steps 14 and 21 indicated no problem, proceed to the next step without replacing the mass air flow meter assembly.

NEXT

31.CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED

Connect the intelligent tester to the DLC3.

Turn the engine switch on (IG).

Turn the tester on.

Clear the DTCs (Click here).

Turn the engine switch off.

Turn the engine switch on (IG) and turn the tester on.

Start the engine and warm it up.

Drive the vehicle in accordance with the driving pattern described in Confirmation Driving Pattern.

Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.

Input the DTC: P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307 or P0308.

Check the DTC judgment result.

Result
Display (DTC Output)
Proceed to
NORMAL
(No DTC output)
A
ABNORMAL
(P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307 or P0308 output)
B

REPLACE ECM (Click here)

END

32.CHANGE TO CHANGE TO NORMAL SPARK PLUG AND CHECK SPARK OF MISFIRING CYLINDER

Change the installed spark plug to a spark plug that functions normally.

Perform a spark test.
CAUTION:
Always disconnect all injector connectors.
NOTICE:
Do not crank the engine for more than 2 seconds.
1. Install the spark plug to the ignition coil and connect the ignition coil connector.
2. Disconnect the injector connector.
3. Ground the spark plug.
4. Check if sparks occur while the engine is being cranked.
  OK:
  Sparks jump across electrode gap.

Go to step 33

REPLACE SPARK PLUG (Click here)

33.CHANGE TO NORMAL IGNITION COIL AND CHECK SPARK OF MISFIRING CYLINDER

Change the ignition coil to an ignition coil that functions normally.

Perform a spark test.
CAUTION:
Always disconnect all injector connectors.
NOTICE:
Do not crank the engine for more than 2 seconds.
1. Install the spark plug to the ignition coil and connect the ignition coil connector.
2. Disconnect the injector connector.
3. Ground the spark plug.
4. Check if sparks occur while the engine is being cranked.
  OK:
  Sparks jump across electrode gap.

REPLACE ECM (Click here)

REPLACE IGNITION COIL (Click here)

34.CHECK FUEL LINE

Check the fuel lines for leaks or blockage.

REPAIR OR REPLACE FUEL LINE

REPLACE FUEL PUMP ASSEMBLY (Click here)

Engine Speed	Duration
Idling	8 minutes or more
1000	4.5 minutes or more
2000	2.5 minutes or more
3000	1.5 minute or more

Display (DTC Output)	Proceed to
ABNORMAL (P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307 or P0308 output)	A
NORMAL (No DTC output)	B