Code No. P0300: Random/Multiple Cylinder Misfire Detected <Except Euro 2>

OPERATION

Check code No. P0261: No. 1 injector circuit low input (Refer to ).
Check code No. P0264: No. 2 injector circuit low input (Refer to ).
Check code No. P0267: No. 3 injector circuit low input (Refer to ).
Check code No. P0270: No. 4 injector circuit low input (Refer to ).
Check code No. P0273: No. 5 injector circuit low input (Refer to ).
Check code No. P0276: No. 6 injector circuit low input (Refer to ).

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 JUDGEMENT

Check Conditions

Engine speed is more than 440 r/min and is less than 4,500 r/min.
Engine coolant temperature is more than -10°C.
Barometric pressure is more than 76 kPa.
Volumetric efficiency is more than 11.3 %.
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 Criterion (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).

Misfire has occurred a predetermined value (2 %) or more in the first 1,000 revolutions from engine start-up (corresponding to 1.5 times the limit of emission standard).

After the first 1,000 revolutions, the following criterion is satisfied 4 times cumulatively. Misfire counts per 1,000 revolutions exceeds a predetermined value (2 %) (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.

PROBABLE CAUSES

Ignition system related part(s) failed
Failed crank angle sensor
Failed injector
Incorrect air-fuel ratio
Low compression pressure
Failed engine coolant temperature sensor
Skipping of timing belt teeth.
Air drawn in from gaps in gasket, seals, etc.
Failed engine-ECU

DIAGNOSIS PROCEDURE

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

Item 2: 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. Check code No. P0335: crank angle sensor system (Refer to ).

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

Data list reference table (Refer to ).

Item 6: Engine coolant temperature sensor
Item 26: Long-term fuel trim 1
Item 27: Long-term fuel trim 2
Item 28: Short-term fuel trim 1
Item 29: Short-term fuel trim 2

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 value. Inspection chart for diagnosis code (Refer to ).

STEP 3. Visual check of ignition spark.

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

Q. Is the check result normal?

	Go to Step 5.

	Go to Step 4.

STEP 4. Check spark plug.

Spark plug check (Refer to GROUP 16 - Ignition System - On-vehicle Service - Spark Plug Check and Cleaning ).

Q. Is the check result normal?

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

	Replace the spark plug.

STEP 5. Check injector itself.

Injector check (Refer to ).

Q. Is the check result normal?

	Go to Step 6.

	Replace the injector.

STEP 6. Check compression pressure.

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

Q. Is the check result normal?

	Go to Step 7.

	Repair.

STEP 7. Check for intake air from intake hose and inlet manifold.

Q. Is the check result normal?

	Go to Step 8.

	Repair.

STEP 8. Check for skipped timing belt teeth.

Q. Is the check result normal?

	Go to Step 9.

	Repair.

STEP 9. M.U.T.-III diagnosis code

Reconfirmation of diagnosis code.

Q. Is diagnosis code stored?

	Replace the engine-ECU.

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