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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 6,594 r/min.
  • Engine coolant temperature is higher than 20°C (68°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.
Judgment 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
  • Misfire has occurred in 1.5 percent or more in the first 1,000 revolutions from engine start-up (corresponding to 1.5 times the limit of emission standard).
or
  • After the first 1,000 revolutions, the following criterion is satisfied 4 times cumulatively.
  • Misfire counts per 1,000 revolutions exceeds in 1.5 percent.
 
 
FAIL-SAFE AND BACKUP FUNCTION
  • The supply of fuel to the misfiring cylinder can possibly be cut.
 
 
OBD-II DRIVE CYCLE PATTERN
  • Refer to Diagnostic Function - OBD-II Drive Cycle - Pattern 15 .
 
 
TROUBLESHOOTING HINTS (The most likely causes for this code to be stored are: )
  • Included air due to lack of fuel
  • Ignition system related part(s) failed.
  • Crankshaft position sensor failed.
  • Incorrect air/fuel ratio.
  • Low compression pressure.
  • Skipping of timing chain teeth.
  • ECM failed.

 
 
DIAGNOSIS
Required Special Tools:
  • MB992744: Vehicle Communication Interface-Lite (V.C.I.-Lite)
  • MB992745: V.C.I.-Lite Main Harness A
  • MB992747: V.C.I.-Lite USB Cable Short
  • MB992748: V.C.I.-Lite USB Cable Long
  • MB991958: Scan Tool (M.U.T.-III Sub Assembly)
    • MB991824: Vehicles Communication Interface (V.C.I.)
    • MB991827: M.U.T.-III USB Cable
    • MB991910: M.U.T.-III Main Harness A (Vehicles with CAN communication system)
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.
Has the user ever experienced the lack of fuel?
Erase the diagnostic trouble codes to finish the check.
Go to Step 2.
 
STEP 2. Using scan tool (M.U.T.-III), check data list item 2: Crankshaft Position Sensor.
cautionTo prevent damage to scan tool (M.U.T.-III), always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool (M.U.T.-III).
(1) Connect scan tool (M.U.T.-III). Refer to HOW TO CONNECT THE SCAN TOOL (M.U.T.-III) .
(2) Start the engine and run at idle.
(3) Set scan tool (M.U.T.-III) to the data reading mode for item 2, Crankshaft Position Sensor.
  • The tachometer and engine speed indicated on the scan tool should match.
(4) Turn the ignition switch to the "LOCK" (OFF) position.
Is the sensor operating properly?
Go to Step 3.
Refer to, DTC P0335 - Crankshaft Position Sensor Circuit .
 
STEP 3. Using scan tool (M.U.T.-III), check data list item 26: Long-Term Fuel Trim.
(1) Start the engine and run at idle.
(2) Set scan tool (M.U.T.-III) to the data reading mode for item 26, 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.
(3) Turn the ignition switch to the "LOCK" (OFF) position.
Is the specification normal?
Go to Step 4.
Refer to DTC P0171 - System too Lean , DTC P0172 - System too Rich .
 
STEP 4. Using scan tool (M.U.T.-III), check data list item 28: Short-Term Fuel Trim.
(1) Start the engine and run at idle.
(2) Set scan tool (M.U.T.-III) to the data reading mode for item 28, Short-Term Fuel Trim.
  • The fuel trim should be between -25 and +25 percent when the engine is 2,500 r/min (during closed loop) after the engine is warmed.
(3) Turn the ignition switch to the "LOCK" (OFF) position.
Is the specification normal?
Go to Step 5.
Refer to DTC P0171 - System too Lean , DTC P0172 - System too Rich .
 
STEP 5. Visual check of ignition spark.
(1) Remove the spark plug and install it to the ignition coil.
(2) Connect the ignition coil connector.
(3) Remove all injector connector.
(4) At the engine start, check each spark plug produces a spark.
Did it spark?
Go to Step 7.
Go to Step 6.
 
STEP 6. Check the spark plugs.
Refer to GROUP 16, Ignition System - On-vehicle Service - Spark Plug Check And Cleaning .
Is the spark plug normal?
Refer to Symptom Procedures - Ignition Circuit System .
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.
  1. Check for skipped timing chain teeth.
  2. Check compression.
Are there any abnormalities?
Repair or replace it. Then go to Step 9.
Go to Step 8.
 
STEP 8. 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 .
(2) Check the diagnostic trouble code (DTC).
Is DTC P0300 stored?
Replace the ECM (Refer to Removal and Installation ). Then go to Step 9.
It can be assumed that this malfunction is intermittent. Refer to GROUP 00, 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 Diagnostic Function - OBD-II Drive Cycle - Pattern 15 .
(2) Check the diagnostic trouble code (DTC).
Is DTC P0300 stored?
Retry the troubleshooting.
The inspection is complete.