P0303
DTC P0300 Random / Multiple Cylinder Misfire DetectedDTC 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
DTC P0307 Cylinder 7 Misfire Detected
DTC P0308 Cylinder 8 Misfire Detected
DESCRIPTION
DTC Detection Condition:
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 ECM blinks the MIL. 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 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
Monitor Strategy:
Typical Enabling Conditions:
Typical Malfunction Thresholds:
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 monitored every 200 crankshaft revolutions, occurs once.
- At a normal engine rpm, a catalyst damage misfire, which monitored every 200 crankshaft revolutions, occurs 3 times.
HINT: If a catalyst damage misfire occurs, the ECM informs the driver by flashing the MIL.
MONITOR RESULT
Refer to CHECKING MONITOR STATUS. Checking Monitor Status
Wiring Diagram (Part 1):
Wiring Diagram (Part 2):
Wiring Diagram (Part 3):
CONFIRMATION DRIVING PATTERN
1. Connect the intelligent tester or 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.
6. 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.
7. Drive the vehicle several times with the conditions, such as engine rpm and engine load, shown in MISFIRE RPM (Misfire RPM) and MISFIRE LOAD (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, with the MISFIRE RPM (Misfire RPM) and MISFIRE LOAD (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.
Step 1-2:
Step 3-4:
Step 4(Continued)-6:
Step 6(Continued)-8:
Step 8(Continued)-9:
Step 9(Continued)-14:
Step 15-19:
Step 20-23:
Step 23(Continued)-25:
Step 25(Continued)-26:
Step 26(Continued)-29:
Step 29(Continued)-30:
INSPECTION PROCEDURE
HINT:
- If any DTCs other than misfire DTCs are output, troubleshoot those DTCs first.
- Read freeze frame data using the intelligent tester or Techstream. 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:
a. The fuel level is low.
b. Improper fuel is used.
c. 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 set again by conducting the confirmation driving pattern, after the repairs.
- For 6 and 8 cylinder engines, the ECM intentionally does not set the specific misfiring cylinder DTCs at high engine RPM. If misfires only occur during high engine RPM driving, only DTC P0300 is set.
In the event of DTC P0300 being present, perform the following operations:
a. Clear the DTC.
b. Start the engine and conduct the confirmation driving pattern.
c. Read the misfiring rates of each cylinder or DTC(s) using the tester.
d. Repair the cylinder(s) that has a high misfiring rate or is indicated by the DTC.
e. After finishing repairs, conduct the confirmation driving pattern again, in order to verify that DTC P0300 is not set.
- When either SHORT FT #1 (Short FT #1), LONG FT #1 (Long FT #1), SHORT FT #2 (Short FT #2) or LONG FT #2 (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 (Coolant Temp) in the freeze frame data is less than 75 °C (167 °F), the misfires occurred only while warming up the engine.