Code No. P0303: No. 3 Cylinder Misfire Detected
OPERATION
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.
- 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. |
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Q.
Is the check result normal?
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Go to Step 2 . |
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Check ignition circuit system (Refer to Inspection Procedure 23 ) |
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STEP 2. Connector check: B-103 No. 3 injector connector |
Q.
Is the check result normal?
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Go to Step 3 . |
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Repair or replace the connector. |
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STEP 3. Check No. 3 injector itself. |
Q.
Is the check result normal?
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Go to Step 4 . |
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Replace the No. 3 injector. |
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STEP 4. Connector check: A-23X injector relay connector |
Q.
Is the check result normal?
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Go to Step 5 . |
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Repair or replace the connector. |
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STEP 5. Check harness between A-23X (terminal No. 3) injector relay connector and B-103 (terminal No. 1) No. 3 injector connector. |
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Q.
Is the check result normal?
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Go to Step 6 . |
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Repair the damaged harness wire. |
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STEP 6. Connector check: B-08 engine-ECU connector |
Q.
Is the check result normal?
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Go to Step 7 . |
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Repair or replace the connector. |
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STEP 7. Check harness between B-103 (terminal No. 2) No. 3 injector connector and B-08 (terminal No. 18) engine-ECU connector. |
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Q.
Is the check result normal?
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Go to Step 8 |
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Repair the damaged harness wire. |
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STEP 8. Check compression pressure of No. 3 cylinder. |
Q.
Is the check result normal?
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Go to Step 9 . |
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Repair. |
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STEP 9. M.U.T.-III diagnosis code |
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Q.
Is the diagnosis code set?
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Replace the engine-ECU. |
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Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection
Service Points - How to Cope with Intermittent Malfunctions ). |
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