Code No. P0300: Random/Multiple Cylinder Misfire Detected

OPERATION

Refer to Code No. P0201: No. 1 injector system .
Refer to Code No. P0202: No. 2 injector system .
Refer to Code No. P0203: No. 3 injector system .
Refer to Code No. P0204: No. 4 injector system .

FUNCTION

If a misfire occurs while the engine is running, the engine speed changes for an instant.
The engine-ECU checks for such changes in engine speed.

TROUBLE JUDGMENT

Check Conditions

Engine speed is 500 - 6,500 r/min.
Engine coolant temperature is -10°C or higher.
Barometric pressure is 76 kPa or higher.
Volumetric efficiency is between 30% and 55%.
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.

Judgment Criterion (change in the angular acceleration of the crankshaft is used for misfire detection).

Misfire has occurred more frequently than the limit during the last 200 revolutions (when the catalyst temperature has been 950°C or higher).

Misfire has occurred 15 times or more in the last 1,000 revolutions (that has been equivalent to approximately 1.5 times the emission standard).

PROBABLE CAUSES

Ignition system related part(s) failed
Failed crank angle sensor
Incorrect air-fuel ratio
Low compression pressure
Failed fuel system
Failed engine coolant temperature sensor
Skipping of timing belt teeth.
Failed engine-ECU

DIAGNOSIS PROCEDURE

STEP 1. M.U.T.-III data list

Item No. 3: Crank angle sensor

OK: Keep the engine speed constant to make the pulse width of output waveform constant.

Q. Is the check result normal?

	Go to Step 2 .

	Check crank angle sensor system (Refer to Code No. P0335 ).

STEP 2. M.U.T.-III data list

Refer to Data List Reference Table .

Item No. 8: Engine coolant temperature sensor
Item No. 19: A/F feedback integration
Item No. 20: Air-fuel ratio learning valve of A zone (low load)
Item No. 21: Air-fuel ratio learning valve of B zone (low speed load)

Q. Are the check results normal?

	Go to Step 3 .

	Perform the diagnosis code classified check procedure for the sensor that has shown an abnormal data valve (Refer to Inspection Chart for Diagnosis Code ).

STEP 3. Visual check of ignition spark.

Remove the spark plug and install to the ignition coil.
Connect the ignition coil connector.
Remove all injector connectors.
At the engine start, check each spark plug procedure a spark.

Q. Is the check result normal?

	Go to Step 4 .

	Check ignition circuit system (Refer to Inspection Procedure 24 ).

STEP 4. Connector check: Injector connectors

A-101 (No. 1 injector connector)
A-102 (No. 2 injector connector)
A-123 (No. 3 injector connector)
A-121 (No. 4 injector connector)

Q. Are the check results normal?

Go to Step 5 .

Repair or replace the connector.

STEP 5. Check injector itself.

Check Injector itself (Refer to ).

Q. Is the check result normal?

	Go to Step 6 .

	Replace the injector.

STEP 6. Fuel pressure measurement.

Fuel pressure measurement (Refer to Fuel Pressure Test ).

Q. Is the check result normal?

	Go to Step 7 .

	Repair the fuel pressure.

STEP 7. Check for intake of air from gaps in gasket, seals, etc.

Q. Is the check result normal?

	Go to Step 8 .

	Repair for intake of air from gaps in gasket, seals, etc.

STEP 8. Check for skipped timing belt teeth.

Q. Is the check result normal?

	Go to Step 9 .

	Repair for skipped timing chain teeth.

STEP 9. Check compression pressure.

Check compression pressure (Refer to GROUP 11E - On-vehicle Service - Compression Pressure Check ).

Q. Is the check result normal?

	Go to Step 10 .

	Repair the compression pressure.

STEP 10. M.U.T.-III diagnosis code.

Reconfirmation of diagnosis code.

Q. Is the diagnosis code set?

	Replace the engine-ECU then perform the variant coding (Refer to GROUP 00 - Precautions Before Service - How to Perform Variant Coding ).

	Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).