P0303
The content of this article reflects the changes identified in TSB - 10-13-007.DTC P0303: Cylinder 3 Misfire Detected
TECHNICAL DESCRIPTION
- If a misfire occurs while the engine is running, the engine speed changes for an instant.
- The ECM checks for such changes in engine speed.
DESCRIPTIONS OF MONITOR METHODS
Monitor angular acceleration of crankshaft and detect malfunction when negative variation of the angular acceleration is large.
MONITOR EXECUTION
Continuous
MONITOR EXECUTION CONDITIONS (Other monitor and Sensor)
Other Monitor (There is no temporary DTC stored in memory for the item monitored below)
- Not applicable
Sensor (The sensor below is determined to be normal)
- Camshaft position sensor
- Mass airflow sensor
- Engine coolant temperature sensor
- Intake air temperature sensor
- Barometric pressure sensor
- Throttle position sensor
DTC SET CONDITIONS
Logic Flow Chart:
Check Conditions
- Engine speed is between 440 and 6,500 r/min.
- Engine coolant temperature is higher than -10 °C (14 °F).
- Barometric pressure is higher than 76 kPa (22.4 in.Hg).
- Volumetric efficiency is 30 percent or more.
- Adaptive learning is complete for the vane which generates a crankshaft position signal.
- The engine running conditions involving a rough road, fuel cut and a rapid change of throttle are not monitored.
- The throttle deviation is -0.06 V/25 ms to +0.06 V/10ms.
Judgement Criteria (change in the angular acceleration of the crankshaft is used for misfire detection).
- Misfire has occurred more frequently than allowed during the last 200 revolutions [when the catalyst temperature is higher than 1,000 °C (1,832 °F)].
or
- The occurrence rate of engine misfiring within the 1,000 engine revolutions is more than 1.5%. [California]
- The occurrence rate of engine misfiring within the 1,000 engine revolutions is more than 1.8%. [Except for California]
OBD-II DRIVE CYCLE PATTERN
Refer to MFI Diagnostic Function-OBD-II Drive Cycle-Pattern 15. OBD-II Drive Cycle
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
- Fuel aeration due to low fuel level.
- Spark plug failed.
- Ignition system related part(s) failed.
- Low compression pressure.
- ECM failed.
DIAGNOSIS
Check whether fuel may be aerated due to low fuel level.
^ Check whether users have experienced the lack of fuel or not.
Q: Has the user ever experienced the lack of fuel?
YES: Ensure fuel level is not low, erase the DTC, and re-evaluate for misfire condition using the appropiate OBD-II Drive Cycle Procedure.
NO: Go to Step 1.
STEP 1. Check the No. 3 cylinder ignition coil spark.
1. Remove the intake manifold.
2. Remove the No. 3 cylinder ignition coil.
3. Remove the spark plug and connect to the No.3 cylinder ignition coil.
4. Ground the spark plug side electrode securely.
- When the engine is cranked, the spark plug should spark.
Q: Did it spark?
YES : Go to Step 3.
NO : Go to Step 2.
STEP 2. Check the No. 3 cylinder spark plugs.
Refer to Engine Electrical, Ignition System-On-vehicle Service-Spark Plug Check And Cleaning.
Q: Is the spark plug normal?
YES : Refer to MFI INSPECTION PROCEDURE 24-Ignition Circuit System. Inspection Procedure 24
NO : Replace the No. 3 cylinder spark plug. Then go to Step 5.
STEP 3. Check the compression.
Refer to Engine Mechanical, On-vehicle Service-Compression Pressure Check.
Q: Are there any abnormalities?
YES : Replace it. Then go to Step 5.
NO : Go to Step 4.
STEP 4. Check the trouble symptoms.
1. Carry out a test drive with the drive cycle pattern. Refer to MFI Diagnostic Function-OBD-II Drive Cycle-Pattern 15. OBD-II Drive Cycle
2. Check the diagnostic trouble code (DTC).
Q: Is DTC P0302 set?
YES : Replace the ECM. When the ECM is replaced, register the ID code. Refer to Diagnosis-ID Codes Registration Judgment Table [Vehicles with KOS] or Diagnosis-ID Codes Registration Judgment Table [Vehicles with WCM]. Then go to Step 5.
NO : It can be assumed that this malfunction is intermittent. Refer to General (Body and Chassis), How to Use Troubleshooting/Inspection Service Points-How to Cope with Intermittent Malfunctions.
STEP 5. Test the OBD-II drive cycle.
1. Carry out a test drive with the drive cycle pattern. Refer to MFI Diagnostic Function-OBD-II Drive Cycle-Pattern 15. OBD-II Drive Cycle
2. Check the diagnostic trouble code (DTC).
Q: Is DTC P0303 set?
YES : Retry the troubleshooting.
NO : The inspection is complete.