P0303

1GR-FE ENGINE CONTROL SYSTEM: SFI SYSTEM: P0300: Random / Multiple Cylinder Misfire Detected

DTC P0300 - Random / Multiple Cylinder Misfire Detected

DTC P0301 - Cylinder 1 Misfire Detected

DTC P0302 - Cylinder 2 Misfire Detected

DTC P0303 - Cylinder 3 Misfire Detected

DTC P0304 - Cylinder 4 Misfire Detected

DTC P0305 - Cylinder 5 Misfire Detected

DTC P0306 - Cylinder 6 Misfire Detected

DESCRIPTION





When the engine misfires, high concentrations of hydrocarbons (HC) enter the exhaust gas. High HC concentration levels can cause increase in exhaust emission levels. Extremely 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 this increase 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 ECM blinks the MIL. To monitor misfires, the ECM uses both the VVT sensor and the Crankshaft Position (CKP) sensor. The VVT 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 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.






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.

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.
- An excessive misfiring rate (approximately 20 to 50 misfires per 1,000 crankshaft revolutions) occurs a total of 4 times.

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

- At a high engine rpm, a catalyst damage misfire, which is monitored every 200 crankshaft revolutions, occurs once.
- At a normal engine rpm, a catalyst damage misfire, which is monitored every 200 crankshaft revolutions, occurs 3 times.
HINT: If a catalyst damage misfire occurs, the ECM informs the driver by flashing the MIL.

Misfire Monitor for Mexico Models

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 1000 misfires per 1000 crankshaft revolutions) occurs once.
- An excessive misfiring rate (approximately 500 misfires per 1,000 crankshaft revolutions) occurs a total of 4 times.

The ECM flashes the MIL and sets a DTC when the following condition, which could cause the Three-Way Catalytic Converter (TWC) damage, is detected (2 trip detection logic).

- A catalyst damage misfire, which is monitored every 200 crankshaft revolutions, occurs 3 times.

MONITOR STRATEGY





TYPICAL ENABLING CONDITIONS

Misfire:





Monitor period of emission-related-misfire:





Monitor period of catalyst-damaged-misfire (MIL blinks):





FOR MEXICO MODELS:

Misfire: for Mexico models





Monitor period of emission-related-misfire: for Mexico models





Monitor period of catalyst-damaged-misfire (MIL blinks): for Mexico models





TYPICAL MALFUNCTION THRESHOLDS

Monitor period of emission-related-misfire:





Monitor period of catalyst-damaged-misfire (MIL blinks):





FOR MEXICO MODELS:

Monitor period of emission-related-misfire: for Mexico models





Monitor period of catalyst-damaged-misfire (MIL blinks): for Mexico models





MONITOR RESULT

Refer to CHECKING MONITOR STATUS Mode 6 Data.

WIRING DIAGRAM

Wiring diagram of the ignition system.









CONFIRMATION DRIVING PATTERN

1. Connect a Techstream to the DLC3.
2. Turn the ignition switch ON.
3. Turn the tester ON.
4. Record the DTC(s) and freeze frame data.
5. Using the tester, switch the ECM from normal mode to check mode Check Mode Procedure.
6. 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.
7. 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.
HINT:
- 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.





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

9. Record the DTC(s), freeze frame data and misfire counts.
10. Turn the ignition switch OFF and wait for at least 5 seconds.

INSPECTION PROCEDURE
HINT:
- If any DTCs other than misfire DTCs are output, troubleshoot those DTCs first.
- Read freeze frame data using a Techstream. Freeze frame data record 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:
1. There was insufficient fuel volume in the tank.
2. Improper fuel is used.
3. 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:
1. Clear the DTC DTC Check / Clear.
2. Start the engine and conduct the confirmation driving pattern.
3. Read the misfiring rates of each cylinder or DTC(s) using the tester.
4. Repair the cylinder(s) that has a high misfiring rate or is indicated by the DTC.
5. 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 has occurred only while warming up the engine.
- An extremely imbalanced drive wheel which causes body vibration may cause misfire DTCs detection.

PROCEDURE

1. CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO MISFIRE CODES)
(a) Connect a Techstream to the DLC3.
(b) Turn the ignition switch ON.
(c) Turn the tester ON.
(d) Select the following menu items: Powertrain / Engine and ECT / Trouble Codes.
(e) Read DTCs.
HINT: Write down the DTCs.

Result:





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

B -- GO TO DTC CHART
A -- Continue to next step.
2. READ VALUE USING TECHSTREAM (MISFIRE RPM AND MISFIRE LOAD)
(a) Connect a Techstream to the DLC3.
(b) Turn the ignition switch ON and turn the tester ON.
(c) Select the following menu items: Powertrain / Engine and ECT / Data List / Misfire / Misfire RPM and Misfire Load.
(d) 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 -- Continue to next step.
3. CHECK PCV HOSE CONNECTIONS
OK:
PCV hose is correctly connected and is not damaged.
NG -- REPAIR OR REPLACE PCV HOSE
OK -- Continue to next step.
4. READ VALUE USING TECHSTREAM (CYLINDER MISFIRE RATE)
(a) Select the following menu items: Powertrain / Engine and ECT / Data List / Misfire / Cylinder #1 Misfire Count, #2, #3, #4, #5 and #6
(b) Read each value for Cylinder #1 Misfire Count 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 Count to #6.
(4) If misfire counts are still not displayed, perform steps (c) and (d).
(c) Drive the vehicle with the Misfire RPM and Misfire Load noted in the "READ VALUE USING TECHSTREAM (MISFIRE RPM AND MISFIRE LOAD)" procedures above.
(d) Read the Cylinder #1 Misfire Count to #6 or DTCs displayed on the tester.
Result:





HINT:
- 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 ECT 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.

B -- CHECK AIR INDUCTION SYSTEM
A -- Continue to next step.
5. CHECK SPARK PLUG




(a) Remove the ignition coil and the spark plug of the misfiring cylinder.
(b) Measure the spark plug electrode gap.
Maximum gap:
1.0 to 1.1 mm (0.039 to 0.043 in.)
(c) Check the electrode for carbon deposits.

Recommended spark plug:





NOTE: If the electrode gap is out of standard, replace the spark plug. Do not adjust the electrode gap.
(d) Reinstall the ignition coil and the spark plug.
NG -- REPLACE SPARK PLUG
OK -- Continue to next step.
6. CHECK FOR SPARKS AND IGNITION
(a) Disconnect the fuel injector connectors to prevent the engine from starting.
CAUTION: Always disconnect all fuel injector connectors.
NOTE: Do not crank the engine for more than 2 seconds.
(b) Remove the ignition coil from the cylinder head.
(c) Install the spark plug onto the ignition coil.
(d) Attach the spark plug assembly to the cylinder head.
(e) Crank the engine for less than 2 seconds and check the spark.
OK:
Sparks jump across electrode gap.
(f) Install the ignition coil.
(g) Reconnect the fuel injector connectors.
NG -- CHANGE TO NORMAL SPARK PLUG AND CHECK SPARK OF MISFIRING CYLINDER
OK -- Continue to next step.
7. CHECK CYLINDER COMPRESSION PRESSURE
(a) Measure the cylinder compression pressure of the misfiring cylinder On-Vehicle Inspection.
NG -- CHECK ENGINE TO DETERMINE CAUSE OF LOW COMPRESSION
OK -- Continue to next step.
8. CHECK HARNESS AND CONNECTOR (ECM - FUEL INJECTOR)




(a) Disconnect the fuel injector connector (of the misfiring cylinder).
(b) Disconnect the B3 ECM connector.
(c) Measure the voltage according to the value(s) in the table below.
Standard Voltage:





(d) Turn the ignition switch OFF.
(e) Measure the resistance according to the value(s) in the table below.
Standard Resistance:






NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.
9. INSPECT ECM TERMINAL OF MISFIRING CYLINDER (#10, #20, #30, #40, #50 AND /OR #60 VOLTAGE)




(a) Turn the ignition switch ON.
(b) Measure the voltage according to the value(s) in the table below.
Standard Voltage:






NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR (BATTERY - ECM)
OK -- Continue to next step.
10. CHECK FUEL INJECTOR OF MISFIRING CYLINDER
(a) Check the fuel injector injection (whether fuel volume is high or low, and whether injection pattern is poor) Testing and Inspection.
NG -- REPLACE FUEL INJECTOR ASSEMBLY
OK -- Continue to next step.
11. CHECK VALVE CLEARANCE OF MISFIRING CYLINDER
(a) Check the valve clearance Adjustments.
NG -- ADJUST VALVE CLEARANCE
OK -- Continue to next step.
12. CHECK AIR INDUCTION SYSTEM
(a) Check the air induction system for vacuum leak.
OK:
No leak from air induction system.
NG -- REPAIR OR REPLACE AIR INDUCTION SYSTEM
OK -- Continue to next step.
13. CHECK VALVE TIMING P0011
NG -- ADJUST VALVE TIMING
OK -- Continue to next step.
14. CHECK FUEL PRESSURE
(a) Check the fuel pressure Testing and Inspection.
NG -- CHECK AND REPLACE FUEL PUMP, PRESSURE REGULATOR, FUEL PIPE LINE AND FILTER
OK -- Continue to next step.
15. READ VALUE USING TECHSTREAM (COOLANT TEMP) P0115
NG -- REPLACE ENGINE COOLANT TEMPERATURE SENSOR
OK -- Continue to next step.
16. INSPECT MASS AIR FLOW METER
(a) Inspection mass air flow meter On-Vehicle Inspection.
NG -- REPLACE MASS AIR FLOW METER
OK -- REPLACE ECM
17. CHECK AIR INDUCTION SYSTEM
(a) Check the air induction system for vacuum leak.
OK:
No leak from air induction system.
NG -- REPAIR OR REPLACE AIR INDUCTION SYSTEM
OK -- Continue to next step.
18. CHECK VALVE TIMING P0011
NG -- ADJUST VALVE TIMING
OK -- Continue to next step.
19. CHECK FUEL PRESSURE
(a) Check the fuel pressure Testing and Inspection.
NG -- CHECK AND REPLACE FUEL PUMP, PRESSURE REGULATOR, FUEL PIPE LINE AND FILTER
OK -- Continue to next step.
20. READ VALUE USING TECHSTREAM (COOLANT TEMP) P0115
NG -- REPLACE ENGINE COOLANT TEMPERATURE SENSOR
OK -- Continue to next step.
21. INSPECT MASS AIR FLOW METER
(a) Inspection mass air flow meter On-Vehicle Inspection.
NG -- REPLACE MASS AIR FLOW METER
OK -- Continue to next step.
22. CHECK SPARK PLUG




(a) Remove the ignition coil and the spark plug of the misfiring cylinder.
(b) Measure the spark plug electrode gap.
Maximum gap:
1.0 to 1.1 mm (0.039 to 0.043 in.)
(c) Check the electrode for carbon deposits.

Recommended spark plug:





NOTE: If the electrode gap is out of standard, replace the spark plug. Do not adjust the electrode gap.
(d) Reinstall the ignition coil and the spark plug.
NG -- REPLACE SPARK PLUG
OK -- Continue to next step.
23. CHECK FOR SPARKS AND IGNITION
(a) Disconnect the fuel injector connectors to prevent the engine from starting.
CAUTION: Always disconnect all fuel injector connectors.
NOTE: Do not crank the engine for more than 2 seconds.
(b) Remove the ignition coil from the cylinder head.
(c) Install the spark plug onto the ignition coil.
(d) Attach the spark plug assembly to the cylinder head.
(e) Crank the engine for less than 2 seconds and check the spark.
OK:
Sparks jump across electrode gap.
(f) Install the ignition coil.
(g) Reconnect the fuel injector connectors.
NG -- CHANGE TO NORMAL SPARK PLUG AND CHECK SPARK OF MISFIRING CYLINDER
OK -- Continue to next step.
24. CHECK CYLINDER COMPRESSION PRESSURE
(a) Measure the cylinder compression pressure of the misfiring cylinder On-Vehicle Inspection.
NG -- CHECK ENGINE TO DETERMINE CAUSE OF LOW COMPRESSION
OK -- Continue to next step.
25. CHECK HARNESS AND CONNECTOR (ECM - FUEL INJECTOR)




(a) Disconnect the fuel injector connector (of the misfiring cylinder).
(b) Disconnect the B3 ECM connector.
(c) Measure the voltage according to the value(s) in the table below.
Standard Voltage:





(d) Turn the ignition switch OFF.
(e) Measure the resistance according to the value(s) in the table below.
Standard Resistance:






NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.
26. INSPECT ECM TERMINAL OF MISFIRING CYLINDER (#10, #20, #30, #40, #50 AND /OR #60 VOLTAGE)




(a) Turn the ignition switch ON.
(b) Measure the voltage according to the value(s) in the table below.
Standard Voltage:






NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR (BATTERY - ECM)
OK -- Continue to next step.
27. CHECK FUEL INJECTOR OF MISFIRING CYLINDER
(a) Check the fuel injector injection (whether fuel volume is high or low, and whether injection pattern is poor) Testing and Inspection.
NG -- REPLACE FUEL INJECTOR ASSEMBLY
OK -- Continue to next step.
28. CHECK VALVE CLEARANCE OF MISFIRING CYLINDER
(a) Check the valve clearance Adjustments.
NG -- ADJUST VALVE CLEARANCE
OK -- REPLACE ECM
29. CHANGE TO NORMAL SPARK PLUG AND CHECK SPARK OF MISFIRING CYLINDER
(a) Change the installed spark plug to a spark plug that functions normally.
(b) Perform a spark test.
CAUTION: Always disconnect all fuel 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 fuel 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
OK -- REPLACE SPARK PLUG
30. CHANGE TO NORMAL IGNITION COIL AND CHECK SPARK OF MISFIRING CYLINDER
(a) Change the installed ignition coil to a ignition coil that functions normally.
(b) Perform a spark test.
CAUTION: Always disconnect all fuel 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 fuel 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
OK -- REPLACE IGNITION COIL ASSEMBLY