P0303
DTC P0303: Cylinder 3 Misfire DetectedMISFIRE DETECTED CIRCUIT
- Refer to DTC P0203 - Injector Circuit - Cylinder 3.
CIRCUIT OPERATION
- The injector power is supplied from the MFI relay (terminal No. 4).
- The ECM
TECHNICAL DESCRIPTION
- If a misfire occurs while the engine is running the engine speed changes for an instant.
- The ECM
DESCRIPTIONS OF MONITOR METHODS
Monitor angular acceleration of crankshaft and detect malfunction when negative variation of the angular acceleration is large.
MONITOR EXECUTION
Continuous
MONITOR EXECUTION CONDITIONS (OTHER MONITOR AND SENSOR)
Other Monitor (There is no temporary DTC stored in memory for the item monitored below)
- Not applicable
Sensor (The sensor below is determined to be normal)
- Camshaft position sensor
- Volume airflow sensor
- Engine coolant temperature sensor
- Intake air temperature sensor
- Barometric pressure sensor
- Throttle position sensor
Logic Flow Chart:
DTC SET CONDITIONS
Check Conditions
- Engine speed is between 440 and 6,000 rpm.
- Engine coolant temperature is higher than -10 °C (14 °F).
- Intake air temperature is higher than -10 °C (14 °F).
- Barometric pressure is at between 76 kPa (11psi) and 106 kPa (15 psi).
- Volumetric efficiency is at between 30 and 60 percent.
- 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 -0.059 v/10 ms to +0.059 v/10 ms.
Judgement Criteria (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 higher than 950 °C (1,742 °F).
or
- Misfire has occurred in 20 or more of the last 1,000 revolutions (corresponding to 1.5 times the limit of emission standard).
OBD-LL DRIVE CYCLE PATTERN
Refer to Diagnostic Function - OBD-II Drive Cycle - Procedure 6 - Other Monitor.
TROUBLESHOOTING HINTS (the most likely causes for this code to be set are: )
- Ignition system related part (s) failed.
- Low compression pressure.
- Injector failed.
- ECM failed.
- PCM failed.
- No. 3 cylinder spark plugs failed.
- Harness damage in No. 3 cylinder injector circuit, or connector damage.
DIAGNOSIS
Required Special Tool:
- MB991502: Scan Tool (MUT-II)
STEP 1. Check the No. 3 cylinder spark plug.
CAUTION: Do not attempt to adjust the gap of the platinum plug. Cleaning of the platinum plug may result in damage to the platinum tips. Therefore, if carbon deposits must be removed, use a plug cleaner and complete cleaning within 20 seconds to protect the electrode. Do not use a wire brush.
1. Remove the intake manifold.
2. Check the plug gap and replace if the limit is exceeded.
Standard value: 1.0 - 1.1 mm (0.039 - 0.043 inch)
Limit: 1.3 mm (0.051 inch)
Q: Is the plug gap at the standard value?
YES: Go to Step 2.
NO: Replace the No. 3 cylinder spark plug. Then go to Step 9.
STEP 2. Check the No. 3 cylinder spark plug cable.
1. Check the cap and coating for cracks.
2. Measure the resistance.
Limit: maximum 22 kohm
Q: Is the measured resistance less than 22 kohm?
YES: Go to Step 3.
NO: Replace the No. 3 cylinder spark plug cable. Then go to Step 9.
STEP 3. Check the No. 3 cylinder injector.
1. Disconnect the No. 3 cylinder injector connector B-05.
2. Measure the resistance between injector side connector terminals No. 1 and No. 2.
Standard value: 13 - 16 ohms @ 20 °C (68 °F)
Q: Is the resistance between 13 and 16 ohms?
YES: Go to Step 4.
NO: Replace the No. 3 cylinder injector. Then go to Step 9.
STEP 4. Check connector B-05 at No. 3 cylinder injector and connector B-118 at injector intermediate connector for damage.
Q: Is the connector in good condition?
YES: Go to Step 5.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 9.
STEP 5. Check connector C-111 at ECM
Q: Is the connector in good condition?
YES: Go to Step 6.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 9.
STEP 6. Check for harness damage between No. 3 cylinder injector connector B-05 (terminal No. 2) and ECM connector C-111 (terminal No. 24)
Q: Is the harness wire in good condition?
YES: Go to Step 7.
NO: Repair it. Then go to Step 9.
STEP 7. Check the compression. Refer to On-vehicle Service - Compression Pressure Check .
Q: Are there any abnormalities?
YES: Go to Step 8.
NO: Repair or replace it. Then go to Step 9.
STEP 8. Replace the No. 3 cylinder injector.
1. Replace the No. 1 cylinder injector.
2. Carry out a test drive with the drive cycle pattern. Refer to Diagnostic Function - OBD-II Drive Cycle - Procedure 6 - Other Monitor.
3. Check the diagnostic trouble code (DTC).
Q: Is DTC P0303 set?
YES: Replace the ECM or PCM. Then go to Step 9.
NO: The inspection is complete.
STEP 9. Test the OBD-II drive cycle.
1. Carry out a test drive with the drive cycle pattern. Refer to Diagnostic Function - OBD-II Drive Cycle Procedure 6 - Other Monitor.
2. Check the diagnostic trouble code (DTC).
Q: Is DTC P0303 set?
YES: Retry the troubleshooting.
NO: The inspection is complete.