P0303
DTC P0303: Cylinder 3 Misfire Detected
CAUTION:
If DTC P0303 has been set, TCL related DTC U1120 is also set. After P0303 has been diagnosed, don't forget to erase DTC U1120.
TECHNICAL DESCRIPTION
- If a misfire occurs while the engine is running, the engine speed changes for an instant.
- The PCM 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 500 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 between 30 and 60 percent.
- Adaptive learning is complete for the vane which generates a crankshaft position signal.
- While the engine is running, excluding gear shifting, deceleration and sudden acceleration/deceleration.
- The throttle deviation is -0.06 V/25 ms to +0.06 V/10 ms.
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 1.0 % or more of the last 1,000 revolutions (corresponding to 1.5 times the limit of emission standard).[ California]
- Misfire has occurred in 1.3 % or more of the last 1,000 revolutions (corresponding to 1.5 times the limit of emission standard).[ Except for California]
OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 15 Monitors, Trips, Drive Cycles and Readiness Codes .
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
- Ignition system related part(s) failed.
- Low compression pressure.
- PCM failed.
DIAGNOSIS
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)Disconnect all injector connectors.
(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.
Procedures.
Q. Is the spark plug normal?
YES Refer to, INSPECTION PROCEDURE 30 - Ignition Circuit System Inspection Procedure 26.
NO Replace the No. 3 cylinder spark plug. Then go to Step 5.
STEP 3. Check the compression.
Testing and Inspection.
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 15 Monitors, Trips, Drive Cycles and Readiness Codes.
(2)Check the diagnostic trouble code (DTC).
Q. Is DTC P0303 set?
YES Replace the PCM. When the PCM is replaced, register the encrypted code. Encrypted Code Registration Criteria Table.
Then go to Step 5.
NO It can be assumed that this malfunction is intermittent. 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 Diagnostic Function - OBD-II Drive Cycle - Pattern 15 Monitors, Trips, Drive Cycles and Readiness Codes.
(2)Check the diagnostic trouble code (DTC).
Q. Is DTC P0303 set?
YES Retry the troubleshooting.
NO The inspection is complete.