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
Logic Flow Chart:
Check Conditions
- Engine speed is between 438 and 7,000 r/min.
- Engine coolant temperature is higher than -10°C (14°F).
- Barometric pressure is higher than 76 kPa (22.4 in.Hg).
- The engine load is with in the positive torque load.
- Adaptive learning is complete for the vane which generates a crankshaft position signal.
- While the engine is running, excluding rough road driving [M/T], sudden acceleration/deceleration and fuel shut-off operation.
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
- Misfire has occurred in 2.0 percent or more of the last 1,000 revolutions (corresponding to 1.5 times the limit of emission standard).
FAIL-SAFE AND BACKUP FUNCTION
- The supply of fuel to the misfiring cylinder can possibly be cut.
OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 14. OBD- II Drive Cycle
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
- Fuel aeration due to low fuel level.
- 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. Visual check on ignition spark of No. 3 cylinder.
1. Remove the spark plug and install it to the ignition coil.
2. Connect the ignition coil connector.
3. Remove all injector connector.
4. At the engine start, check spark plug produces a spark.
Q: Did it spark?
YES : Go to Step 3.
NO : Go to Step 2.
STEP 2. Check the No. 3 cylinder spark plug.
Q: Is the spark plug normal?
YES : Refer to, Symptom Procedures 26 -Ignition Circuit System. Inspection Procedure 26
NO : Replace the No. 3 cylinder spark plug. Then go to Step 5.
STEP 3. Check the compression.
Q: Are there any abnormalities?
YES : Repair or 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 Diagnostic Function - OBD-II Drive Cycle - Pattern 14. OBD- II Drive Cycle
2. Check the diagnostic trouble code (DTC).
Q: Is DTC P0303 set?
YES : Replace the ECM. When the ECM is replaced, register the ID code. Then go to Step 5.
NO : It can be assumed that this malfunction is intermittent.
STEP 5. Test the OBD-II drive cycle.
1. Carry out a test drive with the drive cycle pattern. Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 14. 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.