Code No. P0300: Random/Multiple Cylinder Misfire Detected

OPERATION

Check code No. P0261: No. 1 injector circuit low input (Refer to ).
Check code No. P0262: No. 1 injector circuit high input (Refer to ).
Check code No. P0264: No. 2 injector circuit low input (Refer to ).
Check code No. P0265: No. 2 injector circuit high input (Refer to ).
Check code No. P0267: No. 3 injector circuit low input (Refer to ).
Check code No. P0268: No. 3 injector circuit high input (Refer to ).
Check code No. P0270: No. 4 injector circuit low input (Refer to ).
Check code No. P0271: No. 4 injector circuit high 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 JUDGMENT

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 20 % and is less than 40 %. <4B11>
Volumetric efficiency is more than 30 % and is less than 60 %. <4B12>
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 more than 1,000°C).

Misfire has occurred in 15 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.

PROBABLE CAUSES

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

DIAGNOSIS PROCEDURE

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

Data list reference table (Refer to ).

Item 2: Crank angle sensor
Item 5: Intake air temperature sensor
Item 6: Engine coolant temperature sensor
Item 10: Air flow sensor
Item 26: Long-term fuel trim
Item 28: Short-term fuel trim

Q. Are the check results normal?

	YES : Go to Step 2.

	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 2. Visual check of ignition spark.

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

Q. Is the check result normal?

	Go to Step 3.

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

STEP 3. Check injector itself.

No. 1 injector connector
No. 2 injector connector
No. 3 injector connector
No. 4 injector connector
Injector check (Refer to ).

Q. Are the check results normal?

	Go to Step 4.

	Repair or replace the connector or replace the injector.

STEP 4. Check air intake from inlet hose and inlet manifold.

Q. Is the check result normal?

	Go to Step 5.

	Repair.

STEP 5. Fuel pressure measurement.

Fuel pressure test (Refer to )

Q. Is the check result normal?

	Go to Step 6.

	Repair.

STEP 6. Check for skipped timing chain teeth.

Q. Is the check result normal?

	Go to Step 7.

	Replace the timing chain.

STEP 7. Check compression pressure.

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

Q. Is the check result normal?

	Go to Step 8.

	Repair.

STEP 8. Replace the engine-ECU.

After replacing the engine-ECU, reconfirm whether the diagnosis code is set.

Q. Is the diagnosis code set?

	Check for foreign matters (water, diesel fuel, etc.) in fuel and replace if necessary.

	Check end.