SFI SYSTEM (w/o EGR 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 (HC) enter the exhaust gas. Extremely high hydrocarbon concentration levels can cause increases in exhaust emission levels. 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 these increases in emissions and to limit the possibility of thermal damage, the ECM monitors the misfire count. 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 level and could cause emission deterioration, 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 the following conditions 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 connections Vacuum hose connections Ignition system Fuel injector assembly Fuel pressure Mass air flow meter sub-assembly Engine coolant temperature sensor Compression pressure Valve timing PCV valve and hose PCV hose connections Intake system ECM
P0301 P0302 P0303 P0304 P0305 P0306	Misfiring of specific cylinder occurs and one of the following conditions 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 the following conditions 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 connections
Vacuum hose connections
Ignition system
Fuel injector assembly
Fuel pressure
Mass air flow meter sub-assembly
Engine coolant temperature sensor
Compression pressure
Valve timing
PCV valve and hose
PCV hose connections
Intake system
ECM

P0301

P0302

P0303

P0304

P0305

P0306

Misfiring of specific cylinder occurs and one of the following conditions is detected

(2 trip detection logic):

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

When DTCs for misfiring cylinders are randomly 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.

MONITOR DESCRIPTION

The ECM illuminates the MIL and sets 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 20 to 50 misfires per 1000 crankshaft revolutions) occurs once.
After the first 1000 crankshaft revolutions, an excessive misfiring rate (approximately 20 to 60 misfires per 1000 crankshaft revolutions) occurs 4 times in sequential crankshaft revolutions.

The ECM flashes the MIL and sets a DTC when either one of the following conditions, which could cause the three-way catalytic converter damage, is detected (2 trip detection logic).

In every 200 crankshaft revolutions at a high engine speed, the threshold misfiring percentage is recorded once.
In every 200 crankshaft revolutions at a normal engine speed, the threshold misfiring percentage is recorded 3 times.

WIRING DIAGRAM

CONFIRMATION DRIVING PATTERN

Connect the intelligent tester to the DLC3.
Turn the power switch on (IG).
Turn the tester on.
Put the engine in inspection mode Click here.
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 (to #6) Misfire Count) with the engine idling. 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.

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 Speed	Duration
Idling	5 minutes or more
1000	4 minutes or more
1500	3 minutes or more
2500	2 minutes or more

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

Tech Tips

Do not turn the power 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 power switch off and wait for at least 5 seconds.

INSPECTION PROCEDURE

Note

Inspect the fuses for circuits related to this system before performing the following 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. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. 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 Count to Cylinder #6 Misfire Count).
Be sure to confirm that no misfiring cylinder DTCs are set again by conducting the confirmation driving pattern after finishing repairs.
For 6 cylinder engine, the ECM intentionally does not set the specific misfiring cylinder DTCs at high engine speed. If misfires occur only in high engine speed areas, only DTC P0300 is set.

In the event of DTC P0300 being present, perform the following operations:

Clear the DTCs Click here.
Put the engine in inspection mode 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 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 misfires have occurred only while the engine is being warmed up.
An extremely imbalanced drive wheel which causes body vibration may cause misfire DTCs detection.

PROCEDURE

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

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

Read the DTCs.

Result

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

Tech Tips

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

GO TO DTC CHART Click here

CHECK PCV HOSE (HOSE CONNECTIONS)
1. Check the PCV hose connections Click here.
  
  OK
  
  PCV hose is connected correctly and is not damaged.
NG
REPAIR OR REPLACE PCV HOSE

OK
PERFORM ACTIVE TEST USING INTELLIGENT TESTER (MISFIRE RPM AND MISFIRE LOAD)
1. Connect the intelligent tester to the DLC3.
2. Turn the power switch on (IG).
3. Turn the tester on.
4. Put the engine in inspection mode Click here.
5. Enter the following menus: Powertrain / Engine and ECT / Data List / Misfire RPM and Misfire Load.
6. Read and note the Misfire RPM and Misfire Load values.
  
  Note
  
  The Misfire RPM and Misfire Load values indicate the vehicle conditions under which the misfire occurred.
NEXT

OK
PCV hose is connected correctly and is not damaged.

READ VALUE USING INTELLIGENT TESTER (CYLINDER #1 (TO #6) MISFIRE COUNT)

Connect the intelligent tester to the DLC3.
Turn the power switch on (IG).
Turn the tester on (Step "A").
Put the engine in inspection mode Click here.
Enter the following menus: Powertrain / Engine and ECT / Data List / Cylinder #1 Misfire Count, #2, #3, #4, #5 and #6.
Start the engine and allow the engine to idle.
Read each value for Cylinder #1 (to #6) Misfire Count displayed on the tester. If no misfire counts occur in any cylinders, perform steps [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 [A].

Read the Cylinder #1 Misfire Count to Cylinder #4 Misfire Count or DTCs displayed on the intelligent tester [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

Tech Tips

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

CHECK INTAKE SYSTEM Click here

INSPECT SPARK PLUG
1. Inspect the spark plug of the misfiring cylinder Click here.
NG
REPLACE SPARK PLUG Click here

OK
CHECK FOR SPARK AND IGNITION (SPARK TEST)
1. Perform a spark test Click here.
  
  CAUTION:
  
  During the test, disconnect all fuel injector assembly connectors.
  
  Note
  
  Do not crank the engine for more than 2 seconds.
  
  OK
  
  Spark jumps across electrode gap.
NG
CHANGE TO KNOWN GOOD SPARK PLUG AND CHECK SPARK OF MISFIRING CYLINDER Click here

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

OK

OK
Spark jumps across electrode gap.

INSPECT ECM TERMINAL OF MISFIRING CYLINDER (#10, #20, #30, #40, #50 AND/OR #60 VOLTAGE)

Text in Illustration

*1
Front view of wire harness connector

(to ECM)

Disconnect the ECM connector.
Turn the power switch on (IG).

Text in Illustration
*1	Front view of wire harness connector (to ECM)

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

Standard Voltage

Tester Connection	Switch Condition	Specified Condition
D1-19 (#10) - D1-57 (E01)	Power switch on (IG)	11 to 14 V
D1-20 (#20) - D1-57 (E01)	Power switch on (IG)	11 to 14 V
D1-53 (#30) - D1-57 (E01)	Power switch on (IG)	11 to 14 V
D1-49 (#40) - D1-57 (E01)	Power switch on (IG)	11 to 14 V
D1-21 (#50) - D1-57 (E01)	Power switch on (IG)	11 to 14 V
D1-52 (#60) - D1-57 (E01)	Power switch on (IG)	11 to 14 V

Reconnect the ECM connector.

CHECK FUEL INJECTOR CIRCUIT Click here

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

OK
INSPECT INTAKE SYSTEM
1. Check the intake system for vacuum leaks Click here.
  
  OK
  
  No leaks in intake system.
NG
REPAIR OR REPLACE INTAKE SYSTEM

OK
CHECK FUEL PRESSURE
1. Check the fuel pressure Click here.
NG
CHECK FUEL LINE Click here

OK

OK
No leaks in intake system.

READ VALUE USING INTELLIGENT TESTER (COOLANT TEMP)

Connect the intelligent tester to the DLC3.
Turn the power switch on (IG).
Turn the tester on.
Enter the following menus: Powertrain / Engine and ECT / Data List / All Data / Coolant Temp.

Read the Data List 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 95°C (167°F and 203°F)

REPLACE ENGINE COOLANT TEMPERATURE SENSOR Click here

READ VALUE USING INTELLIGENT TESTER (MAF)
1. Connect the intelligent tester to the DLC3.
2. Turn the power switch on (IG).
3. Turn the tester on.
4. Put the engine in inspection mode Click here.
5. Enter the following menus: Powertrain / Engine and ECT / Data List / All Data / MAF and Coolant Temp.
6. Allow the engine to idle until Coolant Temp reaches 75°C (167°F) or higher.
7. Read MAF with the engine speed at 2500 rpm.
  
  Standard
  
  Between 6 gm/sec and 17 gm/sec (shift lever: P).
  
  Tech Tips
  
  During charging control, the engine speed is set at idle. Therefore, the engine speed does not increase when depressing the accelerator pedal. In this case, warm up the engine after charging control has completed.
NG
Click here

OK

Standard
Between 6 gm/sec and 17 gm/sec (shift lever: P).

CHECK VALVE TIMING (CHECK FOR LOOSE OR JUMPED TEETH ON TIMING CHAIN)

Remove the cylinder head cover sub-assemblies RH and LH.
Turn the crankshaft to align the timing marks of the crankshaft.
Align the notch of the crankshaft pulley to the "0" position.
Check if the timing marks of the camshaft pulley and camshaft bearing cap align.

Turn the crankshaft clockwise 360° if the timing marks do not align. Check if they align once again.

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

Text in Illustration
*1	Timing Mark

Reinstall the cylinder head cover sub-assemblies RH and LH.

Click here

ADJUST VALVE TIMING Click here

CHECK INTAKE SYSTEM
1. Check the intake system for vacuum leaks Click here.
  
  OK
  
  No leaks in intake system.
NG
REPAIR OR REPLACE INTAKE SYSTEM

OK
CHECK FUEL PRESSURE
1. Check the fuel pressure Click here.
NG
CHECK FUEL LINE Click here

OK

OK
No leaks in intake system.

READ VALUE USING INTELLIGENT TESTER (COOLANT TEMP)

Connect the intelligent tester to the DLC3.
Turn the power switch on (IG).
Turn the tester on.
Enter the following menus: Powertrain / Engine and ECT / Data List / All Data / Coolant Temp.

Read the Data List 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 95°C (167°F and 203°F)

REPLACE ENGINE COOLANT TEMPERATURE SENSOR Click here

READ VALUE USING INTELLIGENT TESTER (MAF)
1. Connect the intelligent tester to the DLC3.
2. Turn the power switch on (IG).
3. Turn the tester on.
4. Put the engine in inspection mode Click here.
5. Enter the following menus: Powertrain / Engine and ECT / Data List / All Data / MAF and Coolant Temp.
6. Allow the engine to idle until Coolant Temp reaches 75°C (167°F) or higher.
7. Read MAF with the engine speed at 2500 rpm.
  
  Standard
  
  Between 6 gm/sec and 17 gm/sec (shift lever: P).
  
  Tech Tips
  
  During charging control, the engine speed is set at idle. Therefore, the engine speed does not increase when depressing the accelerator pedal. In this case, warm up the engine after charging control has completed.
NG
Click here

OK

CHECK VALVE TIMING (CHECK FOR LOOSE OR JUMPED TEETH ON TIMING CHAIN)

Remove the cylinder head cover sub-assemblies RH and LH.
Turn the crankshaft to align the timing marks of the crankshaft.
Align the notch of the crankshaft pulley to the "0" position.
Check if the timing marks of the camshaft pulley and camshaft bearing cap align.

Turn the crankshaft clockwise 360° if the timing marks do not align. Check if they align once again.

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

Text in Illustration
*1	Timing Mark

Reinstall the cylinder head cover sub-assemblies RH and LH.

ADJUST VALVE TIMING Click here

INSPECT SPARK PLUG
1. Inspect the spark plug of the misfiring cylinder Click here.
NG
REPLACE SPARK PLUG Click here

OK
CHECK FOR SPARK AND IGNITION (SPARK TEST)
1. Perform a spark test Click here.
  
  CAUTION:
  
  During the test, disconnect all fuel injector assembly connectors.
  
  Note
  
  Do not crank the engine for more than 2 seconds.
  
  OK
  
  Spark jumps across electrode gap.
NG
CHANGE TO KNOWN GOOD SPARK PLUG AND CHECK SPARK OF MISFIRING CYLINDER Click here

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

OK

INSPECT ECM TERMINAL OF MISFIRING CYLINDER (#10, #20, #30, #40, #50 AND/OR #60 VOLTAGE)

Text in Illustration

*1
Front view of wire harness connector

(to ECM)

Disconnect the ECM connector.
Turn the power switch on (IG).

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

Standard Voltage

Tester Connection	Switch Condition	Specified Condition
D1-19 (#10) - D1-57 (E01)	Power switch on (IG)	11 to 14 V
D1-20 (#20) - D1-57 (E01)	Power switch on (IG)	11 to 14 V
D1-53 (#30) - D1-57 (E01)	Power switch on (IG)	11 to 14 V
D1-49 (#40) - D1-57 (E01)	Power switch on (IG)	11 to 14 V
D1-21 (#50) - D1-57 (E01)	Power switch on (IG)	11 to 14 V
D1-52 (#60) - D1-57 (E01)	Power switch on (IG)	11 to 14 V

Reconnect the ECM connector.

CHECK FUEL INJECTOR CIRCUIT Click here

CHECK FUEL INJECTOR ASSEMBLY OF MISFIRING CYLINDER
1. Check the fuel injector assembly 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 HARNESS AND CONNECTOR (MASS AIR FLOW METER SUB-ASSEMBLY CONNECTOR CONNECTION)
1. Check the connection and terminal contact pressure of connectors and wire harnesses between the mass air flow meter sub-assembly and ECM Click here.
  
  Tech Tips
  
  Repair any problems.
NEXT

CHECK WHETHER DTC OUTPUT RECURS

Connect the intelligent tester to the DLC3.
Turn the power switch on (IG).
Turn the tester on.
Clear the DTC Click here.
Turn the power switch off.
Turn the power switch on (IG) and turn the tester on.
Put the engine in inspection mode Click here.
Start the engine and warm it up.
Drive the vehicle in accordance with the driving pattern described in the Confirmation Driving Pattern.
Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.
Input the DTC: P0300, P0301, P0302, P0303, P0304, P0305 or P0306.

Check the DTC judgment result.

Result

Proceed to

ABNORMAL

(DTC P0300, P0301, P0302, P0303, P0304, P0305 or P0306 is output)

NORMAL

(DTC is not output)

END

CHECK HARNESS AND CONNECTOR (MASS AIR FLOW METER SUB-ASSEMBLY - ECM)

Disconnect the mass air flow meter sub-assembly connector.
Disconnect the ECM connector.

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

Standard Resistance (Check for Open)

Tester Connection	Condition	Specified Condition
D3-5 (VG) - D1-121 (VG)	Always	Below 1 Ω
D3-4 (E2G) - D1-120 (E2G)	Always	Below 1 Ω

Standard Resistance (Check for Short)

Tester Connection	Condition	Specified Condition
D3-5 (VG) or D1-121 (VG) - Body ground	Always	10 kΩ or higher

Reconnect the mass air flow meter sub-assembly connector.
Reconnect the ECM connector.

REPAIR OR REPLACE HARNESS OR CONNECTOR (MASS AIR FLOW METER SUB-ASSEMBLY - ECM)

REPLACE MASS AIR FLOW METER SUB-ASSEMBLY
1. Replace the mass air flow meter sub-assembly Click here.
  
  Tech Tips
  
  If the results of the inspections performed in steps 13 and 18 indicated no problem, proceed to the next step without replacing the mass air flow meter sub-assembly.
NEXT

CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED

Connect the intelligent tester to the DLC3.
Turn the power switch on (IG).
Turn the tester on.
Clear the DTC Click here.
Turn the power switch off.
Turn the power switch on (IG) and turn the tester on.
Put the engine in inspection mode Click here.
Start the engine and warm it up.
Drive the vehicle in accordance with the driving pattern described in the Confirmation Driving Pattern.
Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.
Input the DTC: P0300, P0301, P0302, P0303, P0304, P0305 or P0306.

Check the DTC judgment result.

Result

Proceed to

NORMAL

(DTC is not output)

ABNORMAL

(DTC P0300, P0301, P0302, P0303, P0304, P0305 or P0306 is output)

REPLACE ECM Click here

END

CHANGE TO KNOWN GOOD SPARK PLUG AND CHECK SPARK OF MISFIRING CYLINDER
1. Change the installed spark plug to a known good spark plug.
2. Perform a spark test Click here.
  
  CAUTION:
  
  During the test, disconnect all fuel injector assembly connectors.
  
  Note
  
  Do not crank the engine for more than 2 seconds.
  
  OK
  
  Spark jumps across electrode gap.
NG
CHECK FUEL LINE Click here

OK

REPLACE SPARK PLUG Click here
CHANGE TO KNOWN GOOD IGNITION COIL ASSEMBLY AND CHECK SPARK OF MISFIRING CYLINDER
1. Change the installed ignition coil assembly to a known good ignition coil assembly.
2. Perform a spark test Click here.
  
  CAUTION:
  
  During the test, disconnect all fuel injector assembly connectors.
  
  Note
  
  Do not crank the engine for more than 2 seconds.
  
  OK
  
  Spark jumps across electrode gap.
NG
REPLACE ECM Click here

OK

REPLACE IGNITION COIL ASSEMBLY Click here
CHECK FUEL LINE
1. Check the fuel lines for leaks or blockage.
NG
REPAIR OR REPLACE FUEL LINE

OK

REPLACE FUEL PUMP Click here