P0303
The content of this article reflects the changes identified in TSB - 10-13-007.DTC P0301: Cylinder 1 Misfire Detected, DTC P0302: Cylinder 2 Misfire Detected, DTC P0303: Cylinder 3 Misfire Detected, DTC P0304: Cylinder 4 Misfire Detected
TECHNICAL DESCRIPTION
- If a misfire occurs while the engine is running, the engine speed changes for an instant.
- The ECM
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 500 and 6,500 r/min.
- Engine coolant temperature is higher than -10 degrees C (14 degrees F).
- Barometric pressure is higher than 76 kPa (22.4 in.Hg).
- Volumetric efficiency is at between 30 and 55 percent.
- Adaptive learning is complete for the vane which generates a crankshaft position signal.
- While the engine is running, excluding gear shifting, deceleration, sudden acceleration/deceleration and A/C compressor switching.
- The throttle deviation is -0.06 V/10 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 950 degrees C (1,742 degrees F)].
or
- Misfire has occurred in 13 or more of the last 1,000 revolutions (corresponding to 1.5 times the limit of emission standard).
OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 14 OBD-II Drive Cycle Pattern Lists.
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.
- PCM 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 ignition coil spark.
1. Remove the ignition coil.
2. Remove the spark plug and connect to the ignition coil.
3. 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 spark plugs.
CAUTION: Do not attempt to adjust the gap of the iridium plug. Cleaning of the iridium plug may result in damage to the iridium tip. Therefore, if carbon deposits must be removed, use a plug cleaner and complete cleaning within 20 seconds to protect the electrode. Do not use a wire brush.
1. Check the plug gap and replace if the limit is exceeded.
Standard value: 0.7 - 0.8 mm (0.028 - 0.031 inch)
Limit: 1.0 mm (0.039 inch)
Q: Is the plug gap at the standard value?
YES: Refer to, INSPECTION PROCEDURE 33 Ignition Circuit System Inspection Procedure 33.
NO: Replace the spark plug. Then go to Step 5.
STEP 3. Check the compression.
Refer to, On-Vehicle Service - Compression Pressure Check in Engine/Compression Check/Testing and Inspection.
Q: Refer to, On-Vehicle Service - Compression Pressure Check in Engine/Compression Check/Testing and Inspection.
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 Pattern Lists.
2. Check the diagnostic trouble code (DTC).
Q: Are DTC P0301, P0302, P0303 and P0304 set?
YES: Replace the ECM or the PCM. 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 Pattern Lists.
2. Check the diagnostic trouble code (DTC).
Q: Are DTC P0301, P0302, P0303 and P0304 set?
YES: Retry the troubleshooting.
NO: The inspection is complete.