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 EXECUTION

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 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)].

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

TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)

Included air due to lack of fuel.
Ignition system related part(s) failed.
Low compression pressure.
ECM failed.

DIAGNOSIS

STEP 1. Check whether air is included due to the lack of fuel or not.

Check whether users have experienced the lack of fuel or not.

Q. Has the user ever experienced the lack of fuel?

	Erase the diagnosis codes to finish the check.

	Go to Step 2.

STEP 2. 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?

Go to Step 4.

Go to Step 3.

STEP 3. Check the No. 3 cylinder spark plug.

Refer to GROUP 16, Ignition System - On-vehicle Service - Spark Plug Check And Cleaning

Q. Is the spark plug normal?

	Refer to, Symptom Procedures 26 - Ignition Circuit System .

	Replace the No. 3 cylinder spark plug. Then go to Step 6.

STEP 4. Check the compression.

Refer to GROUP 11A, On-vehicle Service - Compression Pressure Check

Q. Are there any abnormalities?

	Repair or replace it. Then go to Step 6.

	Go to Step 5.

STEP 5. 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

(2)Check the diagnostic trouble code (DTC).

Q. Is DTC P0303 set?

	Replace the ECM. When the ECM is replaced, register the ID code. Refer to GROUP 42B, ID Code Registration Necessity Judgment Table <Vehicles with KOS> or GROUP 42C, ID Codes Registration Judgment Table <Vehicles with WCM> . Then go to Step 6.

	It can be assumed that this malfunction is intermittent. Refer to GROUP 00, How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions .

STEP 6. 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

(2)Check the diagnostic trouble code (DTC).

Q. Is DTC P0303 set?

	Retry the troubleshooting.

	The inspection is complete.