P0300
The content of this article reflects the changes identified in TSB - 10-13-007.DTC P0300: Random/Multiple Cylinder Misfire Detected
TECHNICAL DESCRIPTION
- If a misfire occurs while the engine is running, the engine speed changes for an instant.
- The ECM checks for such changes in engine speed.
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
- Mass airflow sensor
- Engine coolant temperature sensor
- Intake air temperature sensor
- Barometric pressure sensor
- Throttle position sensor
DTC SET CONDITIONS
Logic Flow Chart:
Check Conditions
- Engine speed is between 440 and 6,500 r/min.
- Engine coolant temperature is higher than -10 °C (14 °F).
- Barometric pressure is higher than 76 kPa (22.4 in.Hg).
- Volumetric efficiency is 30 percent or more.
- Adaptive learning is complete for the vane which generates a crankshaft position signal.
- The engine running conditions involving a rough road, fuel cut and a rapid change of throttle are not monitored.
- The throttle deviation is -0.06 V/25 ms to +0.06 V/10ms.
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 1,000 °C (1,832 °F)].
or
- The occurrence rate of engine misfiring within the 1,000 engine revolutions is more than 1.5%. [California]
- The occurrence rate of engine misfiring within the 1,000 engine revolutions is more than 1.8%. [Except for California]
OBD-II DRIVE CYCLE PATTERN
Refer to MFI Diagnostic Function-OBD-II Drive Cycle-Pattern 15. OBD-II Drive Cycle
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.
- Poor crankshaft position sensor.
- Incorrect air/fuel ratio.
- Spark plug failed.
- Low compression pressure.
- Skipping of timing belt teeth.
- EGR valve (stopper motor) failed.
- ECM failed.
DIAGNOSIS
Required Special Tools:
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: USB Cable
- MB991910: Main Harness A
- MB992110: Power Plant ECU Check Harness
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 EGR system
Refer to Emission Control-Exhaust Gas Recirculation (EGR) System-General Information (Exhaust Gas Recirculation System).
Q: Are there any abnormalities?
YES : Replace the EGR valve (stopper motor). Then go to Step 9.
NO : Go to Step 2.
STEP 2. Using scan tool MB991958, check data list item 2: Crankshaft Position Sensor.
CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.
1. Connect scan tool MB991958 to the data link connector.
2. Start the engine and run at idle.
3. Set scan tool MB991958 to the data reading mode for item 2, Crankshaft Position Sensor.
4. Check the waveform of the crankshaft position sensor while keeping the engine speed constant.
- The pulse width should be constant.
Q: Is the sensor operating properly?
YES : Go to Step 3.
NO : Refer to MFI DTC P0335-Crankshaft Position Sensor Circuit. P0335
STEP 3. Using scan tool MB991958, check data list item 26 [bank 1> and 27 [bank2>: Long-Term Fuel Trim.
1. Start the engine and run at idle.
2. Set scan tool MB991958 to the data reading mode for item 26[bank 1> and 27 [bank2>, Long-Term Fuel Trim.
- The fuel trim should be between -12.5 and +12.5 percent when the engine is 2,500 r/min (during closed loop) after the engine is warmed.
Q: Is the specification normal?
YES : Go to Step 4.
NO : Refer to MFI DTC P0171-System too Lean (bank 1), P0171 DTC P0172-System too Rich (bank 1), P0172 DTC P0174-System too Lean (bank 2), P0174 DTC P0175-System too Rich (bank 2). P0175
STEP 4. Using scan tool MB991958, check data list item 28 [bank 1> and 29 [bank2>: Short-Term Fuel Trim.
1. Start the engine and run at idle.
2. Set scan tool MB991958 to the data reading mode for item 28[bank 1> and 29 [bank2>, Short-Term Fuel Trim.
- The fuel trim should be between -7.4 and 7.4 percent when the engine is 2,500 r/min (during closed loop) after the engine is warmed.
Q: Is the specification normal?
YES : Go to Step 5.
NO : Refer to MFI, DTC P0171-System too Lean (bank 1), P0171 DTC P0172-System too Rich (bank 1), P0172 DTC P0174-System too Lean (bank 2), P0174 DTC P0175-System too Rich (bank 2). P0175
STEP 5. Check the each ignition coil spark.
1. Remove the intake manifold.
2. Remove the ignition coil.
3. Remove the spark plug and connect to the ignition coil.
4. Ground the spark plug side electrode securely.
- When the engine is cranked, the spark plug should spark.
Q: Did it spark?
YES : Go to Step 7.
NO : Go to Step 6.
STEP 6. Check the spark plugs.
Refer to Engine Electrical, Ignition System-On-vehicle Service-Spark Plug Check And Cleaning.
Q: Is the spark plug normal?
YES : Refer to MFI INSPECTION PROCEDURE 24-Ignition Circuit System. Inspection Procedure 24
NO : Replace the faulty spark plug. Then go to Step 9.
STEP 7. Check the following items.
1. Check the following items, and repair or replace the defective component.
a. Check for skipped timing belt teeth.
b. Check compression.
c. EGR valve failed.
Q: Are there any abnormalities?
YES : Repair it. Then go to Step 9.
NO : Go to Step 8.
STEP 8. Check the trouble symptoms.
1. Carry out a test drive with the drive cycle pattern. Refer to MFI Diagnostic Function-OBD-II Drive Cycle-Pattern 15. OBD-II Drive Cycle
2. Check the diagnostic trouble code (DTC).
Q: Is DTC P0300 set?
YES : Replace the ECM. When the ECM is replaced, register the ID code. Refer to Diagnosis-ID Codes Registration Judgment Table [Vehicles with KOS] or Diagnosis-ID Codes Registration Judgment Table [Vehicles with WCM]. Then go to Step 9.
NO : It can be assumed that this malfunction is intermittent. Refer to General (Body and Chassis), How to Use Troubleshooting/Inspection Service Points-How to Cope with Intermittent Malfunctions.
STEP 9. Test the OBD-II drive cycle.
1. Carry out a test drive with the drive cycle pattern. Refer to MFI Diagnostic Function-OBD-II Drive Cycle-Pattern 15. OBD-II Drive Cycle
2. Check the diagnostic trouble code (DTC).
Q: Is DTC P0300 set?
YES : Retry the troubleshooting.
NO : The inspection is complete.