Code No. P0303: No. 3 Cylinder Misfire Detected










OPERATION



  • Refer to Code No. P0203: No. 3 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 more than 440 r/min and is less than 6,500 r/min.
  • Engine coolant temperature is more than -10°C.
  • Barometric pressure is more than 76 kPa.
  • Volumetric efficiency is more than 30 % and is less than 60 %.
  • 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 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 ignition circuit system (Refer to Inspection Procedure 23 )

STEP 2. Connector check: B-103 No. 3 injector connector


Q. Is the check result normal?

Go to Step 3 .
Repair or replace the connector.

STEP 3. Check No. 3 injector itself.



  • Check injector itself (Refer to ).

Q. Is the check result normal?

Go to Step 4 .
Replace the No. 3 injector.

STEP 4. Connector check: A-23X injector relay connector


Q. Is the check result normal?

Go to Step 5 .
Repair or replace the connector.

STEP 5. Check harness between A-23X (terminal No. 3) injector relay connector and B-103 (terminal No. 1) No. 3 injector connector.


note Before checking harness, check intermediate connector A-11, and repair if necessary.

  • Check power supply line for damage.

Q. Is the check result normal?

Go to Step 6 .
Repair the damaged harness wire.

STEP 6. Connector check: B-08 engine-ECU connector


Q. Is the check result normal?

Go to Step 7 .
Repair or replace the connector.

STEP 7. Check harness between B-103 (terminal No. 2) No. 3 injector connector and B-08 (terminal No. 18) engine-ECU connector.



  • Check output line for damage.

Q. Is the check result normal?

Go to Step 8
Repair the damaged harness wire.

STEP 8. Check compression pressure of No. 3 cylinder.



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

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 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 ).