P0300
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 438 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).
- The engine load is with in the positive torque load.
- Adaptive learning is complete for the vane which generates a crankshaft position signal.
- While the engine is running, excluding sudden acceleration/deceleration and fuel shut-off operation.
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 higher than 1,000°C (1,832°F)].
or
- The occurrence rate of engine misfiring within the 1,000 engine revolutions is more than 1.7 % [Except for California] or 1.8 % [California].
OBD-II DRIVE CYCLE PATTERN
Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 15 Monitors, Trips, Drive Cycles and Readiness Codes.
TROUBLESHOOTING HINTS (The most likely causes for this code to be set are:)
- Included air due to lack of fuel
- 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
STEP 1. Check whether air is included due to the lack of fuel or not
- Check whether users have experienced the lack of fuel or not.
Q. Has the user ever experienced the lack of fuel?
YES Erase the diagnosis codes to finish the check.
NO Go to Step 2.
STEP 2. Check the EGR system
Description and Operation.
Q. Are there any abnormalities?
YES Replace the EGR valve (stopper motor). Then go to Step 10.
NO Go to Step 3.
STEP 3. 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 4.
NO Refer to DTC P0335 - Crankshaft Position Sensor Circuit P0335.
STEP 4. 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 5.
NO Refer to 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. 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 6.
NO Refer to 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 6. 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 8.
NO Go to Step 7.
STEP 7. Check the spark plugs.
Procedures.
Q. Is the spark plug normal?
YES Refer to INSPECTION PROCEDURE 24 - Ignition Circuit System Inspection Procedure 26.
NO Replace the faulty spark plug. Then go to Step 10.
STEP 8. Check the following items.
(1)Check the following items, and repair or replace the defective component.
1. Check for skipped timing belt teeth.
2. Check compression.
3. EGR valve failed.
Q. Are there any abnormalities?
YES Repair it. Then go to Step 10.
NO Go to Step 9.
STEP 9. Check the trouble symptoms.
(1)Carry out a test drive with the drive cycle pattern. Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 15 Monitors, Trips, Drive Cycles and Readiness Codes.
(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 ID registration procedure manual - ID codes registration judgement table [Vehicles with KOS]
or ID registration procedure manual - ID codes registration judgement table [Vehicles with WCM]. Then go to Step 10.
NO It can be assumed that this malfunction is intermittent. How to Cope With Intermittent Malfunctions.
STEP 10. 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 - Pattern 15 Monitors, Trips, Drive Cycles and Readiness Codes.
(2)Check the diagnostic trouble code (DTC).
Q. Is DTC P0300 set?
YES Retry the troubleshooting.
NO The inspection is complete.