P0303
The content of this article reflects the changes identified in TSB - 10-13-007.Injector Circuit:
Connector: A-21X, B-01, B-02, B-05, B-06, C-49 <M/T>, C-50 <A/T>:
Misfire Detected circuit
CIRCUIT OPERATION
- The injector power is supplied from the MFI relay (terminal 1).
- The ECM or PCM controls the injector by turning the power transistor in the ECM or PCM "ON" and "OFF."
TECHNICAL DESCRIPTION
- If a misfire occurs while the engine is running, the engine speed changes for an instant.
- The ECM or PCM checks for such changes in engine speed.
DTC SET CONDITIONS
Check Conditions
- Five seconds or more have passed after the engine was started.
- Engine speed is between 500 and 6,000 r/min.
- Engine coolant temperature is higher than -10°C (14°F).
- Intake air temperature is higher than -10°C (14°F).
- Barometric pressure is higher than 76 kPa (11 psi).
- 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.
Judgement Criteria (change in the angular acceleration of the crankshaft is used for misfire detection).
- Misfire has occurred in 4 or more of the last 200 revolutions [when the catalyst temperature is higher than 950°C (1,742°F)].
or
- Misfire has occurred in 20 or more of the last 1,000 revolutions (equal to 1.5 times the limit of emission standard).
TROUBLESHOOTING HINTS
The most likely causes for this code to be set are:
- Fuel aeration due to low fuel level.
- Ignition system related part(s) failed.
- Low compression pressure.
- Injector failed.
- ECM failed
- PCM failed.
DIAGNOSIS
Check whether fuel may be aerated due to low fuel level.
^ Check whether users have experienced the lack of fuel or not.
Q: Has the user ever experienced the lack of fuel?
YES: Ensure fuel level is not low, erase the DTC, and re-evaluate for misfire condition using the appropiate OBD-II Drive Cycle Procedure.
NO: Go to Step 1.
STEP 1. Check the spark plugs.
1. Check that the plug is not burned, that the insulator plug is not damaged, and that there are no carbon deposits.
2. If cleaning is required due to carbon deposits. etc., clean using a plug cleaner or wire brush, etc.
3. Check the plug gap using a plug gap gauge.
Standard value: 1.0 - 1.1 mm (0.039 - 0.043 inch)
If within specifications, go to Step 2.
If not within specifications, repair or replace the faulty spark plug. Then go to Step 9.
STEP 2. Check the spark plugs cable.
1. Check the cap and coating for cracks.
2. Measure the resistance.
Limit: maximum 22 kohms
If within specifications, go to Step 3.
If not within specifications, replace the faulty spark plug cable. Then go to Step 9.
STEP 3. Check the injectors.
1. Disconnect each injector connector.
2. Measure the resistance between injector side connector 1 and 2 at each injector.
Standard value: 13 - 16 ohms [at 20°C (68°F)]
If within specifications, go to Step 4.
If not within specifications, replace the faulty injector. Then go to Step 9.
STEP 4. Check harness connectors B-01, B-02, B-05, B-06 at the injector for damage.
if harness connectors B-01, B-02, B-05, B-06 are in good condition, go to Step 5.
If harness connectors B-01, B-02, B-05, B-06 are damaged, repair or replace them.
Refer to Harness Connector Inspection. Then go to Step 9.
STEP 5. Check harness connector C-49 at the ECM
If harness connector C-49
If harness connector C-49
Refer to Harness Connector Inspection. Then go to Step 9.
STEP 6. Check the harness wires between injector connectors B-01, B-02, B-05, B-06 and ECM connector C-49
If the wires between injector connectors B-01, B-02, B-05, B-06 and ECM connector C-49
If the wires between injector connectors B-01, B-02, B-05, B-06 and ECM connector C-49
STEP 7. Check the compression.
Refer to On-vehicle Service - Compression Pressure Check.
If correct, go to Step 8.
If incorrect, repair it. Then go to Step 9.
STEP 8. Replace all the injectors.
1. Replace all the injectors.
2. Carry out a test drive with the drive cycle pattern. Refer to Procedure 6 - Other Monitor.
3. Check for the diagnostic trouble code (DTC).
If correct, replace the ECM or PCM.
If DTC P0301, P0302, P0303, P0304 are not output, the inspection is complete.
If DTC P0301, P0302, P0303, P0304 are output, replace the ECM or PCM. Then go to Step 9.
STEP 9. Test the OBD-II drive cycle.
1. Carry out a test drive with the drive cycle pattern. Refer to Procedure 6 - Other monitor.
2. Read the diagnostic trouble code, and confirm that diagnostic trouble codes P0301, P0302, P0303, P0304 does not reset.