SFI SYSTEM, Diagnostic DTC:P0300, P0301, P0302, P0303, P0304, P0305, P0306

DTC Code	DTC Name
P0300	Random / Multiple Cylinder Misfire Detected
P0301	Cylinder 1 Misfire Detected
P0302	Cylinder 2 Misfire Detected
P0303	Cylinder 3 Misfire Detected
P0304	Cylinder 4 Misfire Detected
P0305	Cylinder 5 Misfire Detected
P0306	Cylinder 6 Misfire Detected

DESCRIPTION

When the engine misfires, high concentrations of hydrocarbons enter the exhaust gas. High hydrocarbons concentration levels can cause increase in exhaust emission levels. Extremely high concentrations of hydrocarbons can also cause increases in the three-way catalytic converter temperature, which may cause damage to the three-way catalytic converter. To prevent this increase in emissions and to limit the possibility of thermal damage, the ECM monitors the misfire rate. When the temperature of the three-way catalytic converter reaches the point of thermal degradation, the ECM blinks the MIL. To monitor misfires, the ECM uses both the VVT sensor and the crankshaft position sensor. The VVT sensor is used to identify any misfiring cylinders and the crankshaft position sensor is used to measure variations in the crankshaft rotation speed. Misfires are counted when the crankshaft rotation speed variations exceed predetermined thresholds. If the misfire count exceeds the threshold levels, the ECM illuminates the MIL and sets a DTC.

DTC No.	DTC Detection Condition	Trouble Area
P0300	Simultaneous misfiring of several cylinders occurs and one of following conditions below is detected (2 trip detection logic): High temperature misfire occurs in three-way catalytic converter (MIL blinks) Emission deterioration misfire occurs (MIL illuminates)	Open or short in engine wire harness Connector connection Vacuum hose connections Ignition system Injector Fuel pressure Mass air flow meter Engine coolant temperature sensor Compression pressure Valve clearance Valve timing PCV valve and hose PCV hose connections Air induction system ECM
P0301 P0302 P0303 P0304 P0305 P0306	Misfiring of specific cylinder occurs and one of following conditions below is detected (2 trip detection logic): High temperature misfire occurs in three-way catalytic converter (MIL blinks) Emission deterioration misfire occurs (MIL illuminates)

DTC No.

DTC Detection Condition

Trouble Area

P0300

Simultaneous misfiring of several cylinders occurs and one of following conditions below is detected (2 trip detection logic):

High temperature misfire occurs in three-way catalytic converter (MIL blinks)
Emission deterioration misfire occurs (MIL illuminates)

Open or short in engine wire harness
Connector connection
Vacuum hose connections
Ignition system
Injector
Fuel pressure
Mass air flow meter
Engine coolant temperature sensor
Compression pressure
Valve clearance
Valve timing
PCV valve and hose
PCV hose connections
Air induction system
ECM

P0301

P0302

P0303

P0304

P0305

P0306

Misfiring of specific cylinder occurs and one of following conditions below is detected (2 trip detection logic):

High temperature misfire occurs in three-way catalytic converter (MIL blinks)
Emission deterioration misfire occurs (MIL illuminates)

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

WIRING DIAGRAM

Wiring diagram of the ignition system.

CONFIRMATION DRIVING PATTERN

Connect the intelligent tester to the DLC3.
Turn the ignition 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 #1 Misfire Rate to Cylinder #6 Misfire Rate) 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 rpm and engine load, shown in, Misfire RPM and Misfire Load in the Data List.

Tech Tips

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

Engine RPM	Duration
Idling	3.5 minutes or more
1000	3 minutes or more
2000	1.5 minutes or more
3000	1 minute or more

Check whether misfires have occurred by checking DTCs and freeze frame data.

Tech Tips

Do not turn the ignition 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 erased.
Record the DTC(s), freeze frame data and misfire counts.
Turn the ignition switch off and wait for at least 5 seconds.

INSPECTION PROCEDURE

Tech Tips

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 ECM as freeze frame data.
If the misfire still cannot be reproduced even though the conditions stored in the ECM as freeze frame data have been reproduced, one of the following factors is considered to be a possible cause of the problem:

There was insufficient fuel volume in the tank.
Improper fuel is used.
The spark plugs have been contaminated.

After finishing repairs, check the misfire counts of the cylinders (Cylinder #1 Misfire Rate to Cylinder #6 Misfire Rate).
Be sure to confirm that no misfiring cylinder DTCs are set again by conducting the confirmation driving pattern after finishing repairs.
For 6 and 8 cylinder engines, the ECM intentionally does not set the specific misfiring cylinder DTCs at high engine RPM. If misfires occur only in high engine RPM areas, only DTC P0300 is set.

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 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 set.

When one of 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 less than 75°C (167°F), the misfire have occurred only while warming up the engine.

PROCEDURE

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

Connect the intelligent tester to the DLC3.
Turn the ignition switch on (IG).
Turn the tester on.
Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

Read DTCs.

Tech Tips

Write down the DTCs.

Result

Display (DTC Output)	Proceed to
P0300, P0301, P0302, P0303, P0304, P0305 and/or P0306	A
P0300, P0301, P0302, P0303, P0304, P0305 and/or P0306 and other DTCs	B

Tech Tips

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

GO TO DTC CHART Click here

READ VALUE USING INTELLIGENT TESTER (MISFIRE RPM AND MISFIRE LOAD)
1. Connect the intelligent tester to the DLC3.
2. Turn the ignition switch on (IG) and turn the tester on.
3. Enter the following menus: Powertrain / Engine and ECT / Data List / Misfire / Misfire RPM and Misfire Load.
4. Read and note the Misfire RPM and Misfire Load values.
  
  Tech Tips
  
  The Misfire RPM and Misfire Load values indicate the vehicle conditions under which the misfire occurred.
NEXT
CHECK PCV HOSE CONNECTIONS

OK

PCV hose is correctly connected and is not damaged.

NG
REPAIR OR REPLACE PCV HOSE

OK

OK
PCV hose is correctly connected and is not damaged.

READ VALUE USING INTELLIGENT TESTER

Enter the following menus: Powertrain / Engine and ECT / Data List / Misfire / Cylinder #1 Misfire Rate, #2, #3, #4, #5 and #6
Read each value for Cylinder #1 Misfire Rate to #6 displayed on the tester. If no misfire counts occur in any cylinders, perform the following procedures:
1. Start the engine and let it idle.
2. Move the shift lever to the D position.
3. Check the Cylinder #1 Misfire Rate to #6.
4. If misfire counts are still not displayed, perform steps (c) and (d).
Drive the vehicle with the Misfire RPM and MISFIRE LOAD (Misfire Load) noted in the "READ VALUE OF INTELLIGENT TESTER Misfire RPM AND Misfire Load)" procedures above.

Read the Cylinder #1 Misfire Rate to #6 or DTCs displayed on the tester.

Result

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

Tech Tips

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.
If the freeze frame data's record of the engine coolant temperature is below 75°C (167°F), the misfire may be detected only when the engine is cold.
If the freeze frame data's record of the Engine Run Time is below 120 seconds, the misfire may be detected immediately after the engine is started.

CHECK AIR INDUCTION SYSTEM Click here

CHECK SPARK PLUG

Remove the ignition coil and the spark plug of the misfiring cylinder.
Measure the spark plug electrode gap.

Maximum gap

1.3 mm (0.0512 in.)

Maximum gap
1.3 mm (0.0512 in.)

Check the electrode for carbon deposits.

Recommended spark plug:
Manufacturer	Product
DENSO	FK20HR11

Note

If the electrode gap is larger than standard, replace the spark plug. Do not adjust the electrode gap.

REPLACE SPARK PLUG Click here

CHECK FOR SPARKS AND IGNITION
1. Disconnect the injector connectors to prevent the engine from starting.
  
  CAUTION:
  
  Always disconnect all injector connectors.
  
  Note
  
  Do not crank the engine for more than 2 seconds.
2. Remove the ignition coil from the cylinder head.
3. Install the spark plug onto the ignition coil.
4. Attach the spark plug assembly to the cylinder head.
5. Crank the engine for less than 2 seconds and check the spark.
  
  OK
  
  Sparks jump across electrode gap.
6. Install the ignition coil.
7. Reconnect the injector connectors.
NG
CHANGE TO NORMAL SPARK PLUG AND CHECK SPARK OF MISFIRING CYLINDER Click here

OK
CHECK CYLINDER COMPRESSION PRESSURE
1. Measure the cylinder compression pressure of the misfiring cylinder Click here.
NG
CHECK ENGINE TO DETERMINE CAUSE OF LOW COMPRESSION

OK

OK
Sparks jump across electrode gap.

CHECK HARNESS AND CONNECTOR (INJECTOR OF MISFIRING CYLINDER POWER SOURCE)

Disconnect the injector connector (of the misfiring cylinder).

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

Standard voltage

Cylinder	Tester Connection	Switch Condition	Specified Condition
No. 1	B13-2 - Body ground	Ignition switch on (IG)	11 to 14 V
No. 2	B14-2 - Body ground	Ignition switch on (IG)	11 to 14 V
No. 3	B15-2 - Body ground	Ignition switch on (IG)	11 to 14 V
No. 4	B16-2 - Body ground	Ignition switch on (IG)	11 to 14 V
No. 5	B17-2 - Body ground	Ignition switch on (IG)	11 to 14 V
No. 6	B18-2 - Body ground	Ignition switch on (IG)	11 to 14 V

REPAIR OR REPLACE HARNESS OR CONNECTOR (INJ NO. 2 FUSE - INJECTOR)

CHECK HARNESS AND CONNECTOR (ECM - INJECTOR OF MISFIRING CYLINDER)

Turn the ignition switch off.

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

Standard resistance

Check for open

Cylinder	Tester Connection	Condition	Specified Condition
No. 1	B13-1 - B3-2 (#10)	Always	Below 1 Ω
No. 2	B14-1 - B3-3 (#20)	Always	Below 1 Ω
No. 3	B15-1 - B3-4 (#30)	Always	Below 1 Ω
No. 4	B16-1 - B3-5 (#40)	Always	Below 1 Ω
No. 5	B17-1 - B3-6 (#50)	Always	Below 1 Ω
No. 6	B18-1 - B3-7 (#60)	Always	Below 1 Ω

Check for short

Cylinder	Tester Connection	Condition	Specified Condition
No. 1	B13-1 - Body ground	Always	10 kΩ or higher
No. 2	B14-1 - Body ground	Always	10 kΩ or higher
No. 3	B15-1 - Body ground	Always	10 kΩ or higher
No. 4	B16-1 - Body ground	Always	10 kΩ or higher
No. 5	B17-1 - Body ground	Always	10 kΩ or higher
No. 6	B18-1 - Body ground	Always	10 kΩ or higher

REPAIR OR REPLACE HARNESS OR CONNECTOR (INJECTOR - ECM)

CHECK FUEL INJECTOR OF MISFIRING CYLINDER
1. Check the injector resistance Click here.
2. Check the injector injection (whether fuel volume is high or low, and whether injection pattern is poor) Click here.
NG
REPLACE FUEL INJECTOR ASSEMBLY Click here

OK
CHECK AIR INDUCTION SYSTEM
1. Check the air induction system for vacuum leakage Click here.
  
  OK
  
  No leakage from air induction system.
NG
REPAIR OR REPLACE AIR INDUCTION SYSTEM

OK

OK
No leakage from air induction system.

CHECK VALVE TIMING

Remove the cylinder head covers RH and LH.
Turn the crankshaft to align the matchmarks of the crankshaft.
Align the notch of the crankshaft pulley to the "0" position.
Check if the matchmarks of the camshaft pulley and camshaft bearing cap align.

Turn the crankshaft clockwise by 360° if the matchmarks do not align. Check if they align once again.

OK
The matchmarks of the camshaft pulley and the camshaft bearing cap align when the notch of the crankshaft pulley is in the "0" position.

ADJUST VALVE TIMING Click here

CHECK FUEL PRESSURE
1. Check the fuel pressure Click here.
NG
CHECK AND REPLACE FUEL PUMP, PRESSURE REGULATOR, FUEL PIPE LINE AND FILTER

OK

READ VALUE USING INTELLIGENT TESTER (COOLANT TEMP)

Connect the intelligent tester to the DLC3.
Turn the ignition switch on (IG).
Turn the tester on.
Select the following menu items: Powertrain / Engine and ECT / Data list / Coolant Temp.

Read the value displayed on the tester.

Standard
Between 80°C and 97°C (176°F and 207°F) with warm engine.

Result

Temperature Displayed	Proceed to
-40°C (-40°F)	A
140°C (284°F) or higher	B
Between 80°C and 97°C (176°F and 207°F)	C

Tech Tips

If there is an open circuit, the intelligent tester indicates -40°C (-40°F).
If there is a short circuit, the intelligent tester indicates 140°C (284°F) or higher.

REPLACE ENGINE COOLANT TEMPERATURE SENSOR Click here

INSPECT MASS AIR FLOW METER
1. Inspect the mass air flow meter Click here.
NG
REPLACE MASS AIR FLOW METER Click here

OK

REPLACE ECM Click here
CHECK AIR INDUCTION SYSTEM
1. Check the air induction system for vacuum leakage Click here.
  
  OK
  
  No leakage from air induction system.
NG
REPAIR OR REPLACE AIR INDUCTION SYSTEM

OK

CHECK VALVE TIMING

Remove the cylinder head covers RH and LH.
Turn the crankshaft to align the matchmarks of the crankshaft.
Align the notch of the crankshaft pulley to the "0" position.
Check if the matchmarks of the camshaft pulley and camshaft bearing cap align.

Turn the crankshaft clockwise by 360° if the matchmarks do not align. Check if they align once again.

OK
The matchmarks of the camshaft pulley and the camshaft bearing cap align when the notch of the crankshaft pulley is in the "0" position.

ADJUST VALVE TIMING Click here

CHECK FUEL PRESSURE
1. Check the fuel pressure Click here.
NG
CHECK AND REPLACE FUEL PUMP, PRESSURE REGULATOR, FUEL PIPE LINE AND FILTER

OK

READ VALUE USING INTELLIGENT TESTER (COOLANT TEMP)

Connect the intelligent tester to the DLC3.
Turn the ignition switch on (IG).
Turn the tester on.
Select the following menu items: Powertrain / Engine and ECT / Data list / Coolant Temp.

Read the value displayed on the tester.

Standard
Between 80°C and 97°C (176°F and 207°F) with warm engine.

Result

Temperature Displayed	Proceed to
-40°C (-40°F)	A
140°C (284°F) or higher	B
Between 80°C and 97°C (176°F and 207°F)	C

Tech Tips

If there is an open circuit, the intelligent tester indicates -40°C (-40°F).
If there is a short circuit, the intelligent tester indicates 140°C (284°F) or higher.

REPLACE ENGINE COOLANT TEMPERATURE SENSOR Click here

INSPECT MASS AIR FLOW METER
1. Inspect the mass air flow meter Click here.
NG
REPLACE MASS AIR FLOW METER Click here

OK

CHECK SPARK PLUG

Remove the ignition coil and the spark plug of the misfiring cylinder.
Measure the spark plug electrode gap.

Maximum gap

1.3 mm (0.0512 in.)

Check the electrode for carbon deposits.

Recommended spark plug:
Manufacturer	Product
DENSO	FK20HR11

Note

If the electrode gap is larger than standard, replace the spark plug. Do not adjust the electrode gap.

REPLACE SPARK PLUG Click here

CHECK FOR SPARKS AND IGNITION
1. Disconnect the injector connectors to prevent the engine from starting.
  
  CAUTION:
  
  Always disconnect all injector connectors.
  
  Note
  
  Do not crank the engine for more than 2 seconds.
2. Remove the ignition coil from the cylinder head.
3. Install the spark plug onto the ignition coil.
4. Attach the spark plug assembly to the cylinder head.
5. Crank the engine for less than 2 seconds and check the spark.
  
  OK
  
  Sparks jump across electrode gap.
6. Install the ignition coil.
7. Reconnect the injector connectors.
NG
CHANGE TO NORMAL SPARK PLUG AND CHECK SPARK OF MISFIRING CYLINDER Click here

OK
CHECK CYLINDER COMPRESSION PRESSURE
1. Measure the cylinder compression pressure of the misfiring cylinder Click here.
NG
CHECK ENGINE TO DETERMINE CAUSE OF LOW COMPRESSION

OK

CHECK HARNESS AND CONNECTOR (INJECTOR OF MISFIRING CYLINDER POWER SOURCE)

Disconnect the injector connector (of the misfiring cylinder).

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

Standard voltage

Cylinder	Tester Connection	Switch Condition	Specified Condition
No. 1	B13-2 - Body ground	Ignition switch on (IG)	11 to 14 V
No. 2	B14-2 - Body ground	Ignition switch on (IG)	11 to 14 V
No. 3	B15-2 - Body ground	Ignition switch on (IG)	11 to 14 V
No. 4	B16-2 - Body ground	Ignition switch on (IG)	11 to 14 V
No. 5	B17-2 - Body ground	Ignition switch on (IG)	11 to 14 V
No. 6	B18-2 - Body ground	Ignition switch on (IG)	11 to 14 V

REPAIR OR REPLACE HARNESS OR CONNECTOR (INJ NO. 2 FUSE - INJECTOR)

CHECK HARNESS AND CONNECTOR (ECM - INJECTOR OF MISFIRING CYLINDER)

Turn the ignition switch off.

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

Standard resistance

Check for open

Cylinder	Tester Connection	Condition	Specified Condition
No. 1	B13-1 - B3-2 (#10)	Always	Below 1 Ω
No. 2	B14-1 - B3-3 (#20)	Always	Below 1 Ω
No. 3	B15-1 - B3-4 (#30)	Always	Below 1 Ω
No. 4	B16-1 - B3-5 (#40)	Always	Below 1 Ω
No. 5	B17-1 - B3-6 (#50)	Always	Below 1 Ω
No. 6	B18-1 - B3-7 (#60)	Always	Below 1 Ω

Check for short

Cylinder	Tester Connection	Condition	Specified Condition
No. 1	B13-1 - Body ground	Always	10 kΩ or higher
No. 2	B14-1 - Body ground	Always	10 kΩ or higher
No. 3	B15-1 - Body ground	Always	10 kΩ or higher
No. 4	B16-1 - Body ground	Always	10 kΩ or higher
No. 5	B17-1 - Body ground	Always	10 kΩ or higher
No. 6	B18-1 - Body ground	Always	10 kΩ or higher

REPAIR OR REPLACE HARNESS OR CONNECTOR (INJECTOR - ECM)

CHECK FUEL INJECTOR OF MISFIRING CYLINDER
1. Check the injector resistance Click here.
2. Check the injector injection (whether fuel volume is high or low, and whether injection pattern is poor) Click here.
NG
REPLACE FUEL INJECTOR ASSEMBLY Click here

OK

REPLACE ECM Click here
CHANGE TO NORMAL SPARK PLUG AND CHECK SPARK OF MISFIRING CYLINDER
1. Change the installed spark plug to a spark plug that functions normally.
2. Perform a spark test.
  
  CAUTION:
  
  Always disconnect all injector connectors.
  
  Note
  
  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.
NG
CHANGE TO NORMAL IGNITION COIL AND CHECK SPARK OF MISFIRING CYLINDER Click here

OK

REPLACE SPARK PLUG Click here
CHANGE TO NORMAL IGNITION COIL AND CHECK SPARK OF MISFIRING CYLINDER
1. Change the installed ignition coil to a ignition coil that functions normally.
2. Perform a spark test.
  
  CAUTION:
  
  Always disconnect all injector connectors.
  
  Note
  
  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.
NG
REPLACE ECM Click here

OK

REPLACE IGNITION COIL Click here