SFI SYSTEM (w/ Electronic Throttle Control System), Diagnostic DTC:P0300, P0301, P0302, P0303

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

DESCRIPTION

When a misfire occurs in the engine, hydrocarbons (HC) enter the exhaust gas in high concentrations. If this HC concentration is high enough, there could be an increase in exhaust emission levels. High concentrations of HC can also cause the temperature of the Three-Way Catalytic Converter (TWC) to increase, possibly damaging the TWC. To prevent this increase in emissions and 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 ECM blinks the MIL. To monitor misfires, the ECM uses both the camshaft position sensor and the crankshaft position sensor. The camshaft position sensor is used to identify misfiring cylinders and the crankshaft position sensor is used to measure variations in the crankshaft rotation speed. The misfire counter increments when the crankshaft rotation speed variations exceed the threshold values.

If the misfiring rate exceeds the threshold and could cause emission deterioration, the ECM illuminates the MIL.

Tech Tips

The ECM monitors misfires, which could cause emission deterioration, every 1000 crankshaft revolutions. When these misfires are detected, the ECM illuminates the MIL and sets a DTC.
The ECM monitors misfires, which could damage the TWC, every 200 crankshaft revolutions. When these misfires are detected, the ECM flashes the MIL and sets a DTC.

DTC No.	DTC Detection Condition	Trouble Area
P0300	Misfiring of random cylinders is detected (2 trip detection logic)	Open or short in engine wire harness Connector connection Ignition system Injector Fuel pressure Manifold absolute pressure sensor Engine coolant temperature sensor Compression pressure Valve clearance Valve timing PCV hose Air induction system ECM
P0301 P0302 P0303	Misfiring of each cylinder is detected (2 trip detection logic)	Open or short in engine wire harness Connector connection Ignition system Injector Fuel pressure Manifold absolute pressure sensor Engine coolant temperature sensor Compression pressure Valve clearance Valve timing PCV hose Air induction system ECM

DTC No.

DTC Detection Condition

Trouble Area

P0300

Misfiring of random cylinders is detected

(2 trip detection logic)

Open or short in engine wire harness
Connector connection
Ignition system
Injector
Fuel pressure
Manifold absolute pressure sensor
Engine coolant temperature sensor
Compression pressure
Valve clearance
Valve timing
PCV hose
Air induction system
ECM

P0301

P0302

P0303

Misfiring of each cylinder is detected

(2 trip detection logic)

Open or short in engine wire harness
Connector connection
Ignition system
Injector
Fuel pressure
Manifold absolute pressure sensor
Engine coolant temperature sensor
Compression pressure
Valve clearance
Valve timing
PCV hose
Air induction system
ECM

Tech Tips

These DTCs are detected when the engine idles for approximately 10 minutes after warm-up. (Misfire can be clearly checked by activating the air conditioning system.)

WIRING DIAGRAM

CONFIRMATION DRIVING PATTERN

Allow the engine to idle for 10 minutes or more.

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 the misfire DTCs are set simultaneously, first troubleshoot them.
If a misfire does not occur when the vehicle is brought to the workshop, a misfire can be confirmed by reproducing the condition of the freeze frame data. Also, after finishing repairs, confirm that misfires do not recur (see the confirmation driving pattern).
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.
When either of Short FT #1 and Long FT #1 in the freeze frame data is over the range of -20%, there is a possibility that the air-fuel ratio is becoming rich (-20% or less) or lean (+20% or more).
When Coolant Temp. in the freeze frame data is less than 75°C (167°F), there is a possibility that misfires occur only during engine warm-up.
If a misfire cannot be reproduced, the following reasons may apply: 1) the vehicle has a lack of fuel, 2) improper fuel is being used, and 3) the ignition plug has been contaminated.
An extremely imbalanced drive wheel which causes body vibration may cause misfire DTCs detection.

PROCEDURE

CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO P0300, P0301, P0302 OR P0303)

Connect the intelligent tester to the DLC3.
Turn the ignition switch to ON.
Turn the tester on.
Enter the following menus: Powertrain / Engine and ECT / DTC.

Read the DTC.

Result

Result	Proceed to
P0300, P0301, P0302 or P0303	A
P0300, P0301, P0302 or P0303 and other DTCs	B

GO TO DTC CHART Click here

CHECK PCV HOSE CONNECTIONS

OK

PCV hose is connected correctly and is not damaged.

NG
REPAIR OR REPLACE PCV HOSE

OK

OK
PCV hose is connected correctly and is not damaged.

CHECK DTCS OUTPUT

Connect the intelligent tester to the DLC3.
Turn the ignition switch to ON and turn the tester on.
Start the engine.

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

Tech Tips

Read the output DTCs and proceed to the appropriate step shown in the table below.

Result

Result	Proceed to
1 DTC (other than DTC P0300)	A
2 DTCs or more (other than DTC P0300)	B

CHECK AIR INDUCTION SYSTEM Click here

INSPECT SPARK PLUG

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

Standard

1.0 to 1.1 mm (0.039 to 0.043 in.)

Maximum gap

1.2 mm (0.047 in.)

Standard
1.0 to 1.1 mm (0.039 to 0.043 in.)

Maximum gap
1.2 mm (0.047 in.)

Check the electrode for carbon deposits.

Recommended Spark Plug
Manufacturer	Product
DENSO	K20HR - U11

Note

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

Reinstall the ignition coil and the spark plug.

REPLACE SPARK PLUG

CHECK FOR SPARKS AND IGNITION
1. Perform a spark test.
  
  CAUTION:
  
  Always disconnect all injector connectors.
  
  Note
  
  Do not crank the engine for more than 5 to 10 seconds.
  1. Remove the ignition coil from the cylinder head.
  2. Install the spark plug onto the ignition coil.
  3. Disconnect all of the fuel injector connectors.
  4. Touch the spark plug to the cylinder head.
  5. Crank the engine for less than 5 seconds and check for spark.
    
    OK
    
    Sparks jump across electrode gap.
  6. Reconnect all of the fuel injector connectors.
  7. Reinstall the ignition coil.
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 (FUEL INJECTOR - ECM)

Disconnect the fuel injector connectors.
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
B25-47 (#1) - B7-1 (Injector)	Always	Below 1 Ω
B25-48 (#2) - B8-1 (Injector)	Always	Below 1 Ω
B25-67 (#3) - B9-1 (Injector)	Always	Below 1 Ω

Standard Resistance (Check for Short)

Tester Connection	Condition	Specified Condition
B25-47 (#1) or B7-1 (Injector) - Body ground	Always	10 kΩ or higher
B25-48 (#2) or B8-1 (Injector) - Body ground	Always	10 kΩ or higher
B25-67 (#3) or B9-1 (Injector) - Body ground	Always	10 kΩ or higher

Reconnect the fuel injector connectors.
Reconnect the ECM connector.

REPAIR OR REPLACE HARNESS OR CONNECTOR

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

Disconnect the ECM connector.
Turn the ignition switch to ON.

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

Standard Voltage

Tester Connection	Switch Condition	Specified Condition
B25-47 (#1) - Body ground	Ignition switch ON	11 to 14 V
B25-48 (#2) - Body ground	Ignition switch ON	11 to 14 V
B25-67 (#3) - Body ground	Ignition switch ON	11 to 14 V

Reconnect the ECM connector.

REPAIR OR REPLACE HARNESS OR CONNECTOR (BATTERY - ECM)

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

OK
CHECK VALVE CLEARANCE OF MISFIRING CYLINDER
1. Check the valve clearance Click here.
NG
ADJUST VALVE CLEARANCE Click here

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

OK
CHECK VALVE TIMING

Tech Tips

Check the valve timing Click here.

NG
ADJUST VALVE TIMING Click here

OK
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)
1. Connect the intelligent tester to the DLC3.
2. Turn the ignition switch to ON and turn the tester on.
3. Enter the following menus: Powertrain / Engine and ECT / Data List / Coolant Temp.
4. Read the value.
  
  Standard
  
  75°C to 97°C (167°F to 207°F) after warming up the engine.
NG
REPLACE ENGINE COOLANT TEMPERATURE SENSOR Click here

OK
INSPECT MANIFOLD ABSOLUTE PRESSURE SENSOR

Tech Tips

Inspect the manifold absolute pressure sensor Click here.

NG
REPLACE MANIFOLD ABSOLUTE PRESSURE SENSOR Click here

OK

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

OK
CHECK VALVE TIMING

Tech Tips

Check the valve timing Click here.

NG
ADJUST VALVE TIMING Click here

OK
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)
1. Connect the intelligent tester to the DLC3.
2. Turn the ignition switch to ON and turn the tester on.
3. Enter the following menus: Powertrain / Engine and ECT / Data List / Coolant Temp.
4. Read the value.
  
  Standard
  
  75°C to 97°C (167°F to 207°F) after warming up the engine.
NG
REPLACE ENGINE COOLANT TEMPERATURE SENSOR Click here

OK
INSPECT MANIFOLD ABSOLUTE PRESSURE SENSOR

Tech Tips

Inspect the manifold absolute pressure sensor Click here.

NG
REPLACE MANIFOLD ABSOLUTE PRESSURE SENSOR Click here

OK

OK
No leaks from air induction system.

Standard
75°C to 97°C (167°F to 207°F) after warming up the engine.

OK
No leaks from air induction system.

INSPECT SPARK PLUG

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

Standard

1.0 to 1.1 mm (0.039 to 0.043 in.)

Maximum gap

1.2 mm (0.047 in.)

Check the electrode for carbon deposits.

Recommended Spark Plug
Manufacturer	Product
DENSO	K20HR - U11

Note

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

Reinstall the ignition coil and the spark plug.

REPLACE SPARK PLUG

CHECK FOR SPARK AND IGNITION
1. Perform a spark test.
  
  CAUTION:
  
  Always disconnect all injector connectors.
  
  Note
  
  Do not crank the engine for more than 5 to 10 seconds.
  1. Remove the ignition coil from the cylinder head.
  2. Install the spark plug onto the ignition coil.
  3. Disconnect all of the fuel injector connectors.
  4. Touch the spark plug to the cylinder head.
  5. Crank the engine for less than 5 seconds and check for spark.
    
    OK
    
    Sparks jump across electrode gap.
  6. Reconnect all of the fuel injector connectors.
  7. Reinstall the ignition coil.
NG
CHANGE TO NORMAL 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

CHECK HARNESS AND CONNECTOR (FUEL INJECTOR - ECM)

Disconnect the fuel injector connectors.
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
B25-47 (#1) - B7-1 (Injector)	Always	Below 1 Ω
B25-48 (#2) - B8-1 (Injector)	Always	Below 1 Ω
B25-67 (#3) - B9-1 (Injector)	Always	Below 1 Ω

Standard Resistance (Check for Short)

Tester Connection	Condition	Specified Condition
B25-47 (#1) or B7-1 (Injector) - Body ground	Always	10 kΩ or higher
B25-48 (#2) or B8-1 (Injector) - Body ground	Always	10 kΩ or higher
B25-67 (#3) or B9-1 (Injector) - Body ground	Always	10 kΩ or higher

Reconnect the fuel injector connectors.
Reconnect the ECM connector.

REPAIR OR REPLACE HARNESS OR CONNECTOR

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

Disconnect the ECM connector.
Turn the ignition switch to ON.

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

Standard Voltage

Tester Connection	Switch Condition	Specified Condition
B25-47 (#1) - Body ground	Ignition switch ON	11 to 14 V
B25-48 (#2) - Body ground	Ignition switch ON	11 to 14 V
B25-67 (#3) - Body ground	Ignition switch ON	11 to 14 V

Reconnect the ECM connector.

REPAIR OR REPLACE HARNESS OR CONNECTOR (BATTERY - ECM)

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

OK
CHECK VALVE CLEARANCE OF MISFIRING CYLINDER
1. Check the valve clearance of misfiring cylinder Click here.
NG
ADJUST VALVE CLEARANCE 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 normally functioning spark plug.
2. Perform a spark test.
  
  CAUTION:
  
  Always disconnect all injector connectors.
  
  Note
  
  Do not crank the engine for more than 5 to 10 seconds.
  1. Remove the ignition coil from the cylinder head.
  2. Install the spark plug onto the ignition coil.
  3. Disconnect all of the fuel injector connectors.
  4. Touch the spark plug to the cylinder head.
  5. Crank the engine for less than 5 seconds and check for spark.
    
    OK
    
    Sparks jump across electrode gap.
  6. Reconnect all of the fuel injector connectors.
  7. Reinstall the ignition coil.
NG
CHANGE TO NORMAL IGNITION COIL AND CHECK SPARK OF MISFIRING CYLINDER Click here

OK

REPLACE SPARK PLUG
CHANGE TO NORMAL IGNITION COIL AND CHECK SPARK OF MISFIRING CYLINDER
1. Change the installed ignition coil to a normally functioning ignition coil.
2. Perform a spark test.
  
  CAUTION:
  
  Always disconnect all injector connectors.
  
  Note
  
  Do not crank the engine for more than 5 to 10 seconds.
  1. Remove the ignition coil from the cylinder head.
  2. Install the spark plug onto the ignition coil.
  3. Disconnect all of the fuel injector connectors.
  4. Touch the spark plug to the cylinder head.
  5. Crank the engine for less than 5 seconds and check for spark.
    
    OK
    
    Sparks jump across electrode gap.
  6. Reconnect all of the fuel injector connectors.
  7. Reinstall the ignition coil.
NG
REPLACE ECM Click here

OK

REPLACE IGNITION COIL