Code No. P0303: No. 3 Cylinder Misfire Detected


OPERATION



  • Check code No. P0267: No. 3 injector circuit low input (Refer to ).
  • Check code No. P0268: No. 3 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. (However, 20°C when the engine coolant temperature at engine start is -10°C or less).
  • Barometric pressure is more than 76 kPa.
  • Volumetric efficiency is more than 20 % and is less than 60 %. <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 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 No. 3 injector
  • Harness damage in No. 3 injector circuit
  • Low compression pressure
  • Failed engine-ECU

DIAGNOSIS PROCEDURE

STEP 1. Visual check of ignition spark on No. 3 cylinder.



  • 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 spark plug produces a spark.

Q. Is the check result normal?
Go to Step 2
Check Inspection Procedure - ignition circuit system (Refer to ).

STEP 2. Check No. 3 injector itself.

  • Injector connector check.
  • Injector check (Refer to ).

Q. Is the check result normal?
Go to Step 3
Repair or replace the connector, replace the No. 3 injector.

STEP 3. Check harness between engine control relay connector terminal and No. 3 injector connector terminal power supply line.

  • Check power supply line for damage.

Q. Is the check result normal?
Go to Step 4
Repair or replace the connector, or repair the damaged harness wire.

STEP 4. Check harness between No. 3 injector connector terminal and engine-ECU connector terminal INJ3.

  • Check output line for damage.

Q. Is the check result normal?
Go to Step 5
Repair or replace the connector, or repair the damaged harness wire.

STEP 5. Check compression pressure of No. 3 cylinder.

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

Q. Is the check result normal?
Go to Step 6
Repair.

STEP 6. M.U.T.-III diagnosis code

  • Reconfirmation of diagnosis code.

Q. Is the diagnosis code set?
Replace the engine-ECU.
Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).