P0300
The content of this article reflects the changes identified in TSB - 10-13-007.DTC P0300: Random/Multiple Cylinder Misfire Detected
CAUTION: If DTC P0300 has been set, TCL related DTC U1120 is also set. After P0300 has been diagnosed, don't forget to erase DTC U1120.
TECHNICAL DESCRIPTION
- If a misfire occurs while the engine is running, the engine speed changes for an instant.
- The ECM [M/T] or the PCM [A/T] 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 500 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 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 -0.6 V/10 ms to +0.6 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 1,000 °C (1,832 °F)].
or
- Misfire has occurred in 14 or more of the last 1,000 revolutions (corresponding to 1.5 times the limit of emission standard). [M/T]
or
- Misfire has occurred in 11 or more of the last 1,000 revolutions (corresponding to 1.5 times the limit of emission standard). [A/T]
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.
- Low compression pressure.
- Skipping of timing belt teeth.
- EGR system and EGR valve failed.
- ECM failed. [M/T]
- PCM failed. [A/T]
DIAGNOSIS
Required Special Tools:
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: USB Cable
- MB991910: Main Harness A
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. 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.
5. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the sensor operating properly?
YES : Go to Step 2.
NO : Refer to DTC P0335 -Crankshaft Position Sensor Circuit. P0335
STEP 2. Using scan tool MB991958, check data list item 26: Cylinder 1, 4 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, Cylinder 1, 4 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.
Q: Is the specification normal?
YES : Go to Step 3.
NO : Refer to DTC P0171 -System too Lean (cylinder 1, 4), P0171 DTC P0172 -System too Rich (cylinder 1, 4). P0172
STEP 3. Using scan tool MB991958, check data list item 27: Cylinder 2, 3 Long-Term Fuel Trim.
1. Start the engine and run at idle.
2. Set scan tool MB991958 to the data reading mode for item 27, Cylinder 2, 3 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.
Q: Is the specification normal?
YES : Go to Step 4.
NO : Refer to DTC P0174 -System too Lean (cylinder 2, 3), P0174 DTC P0175 -System too Rich (cylinder 2, 3). P0175
STEP 4. Using scan tool MB991958, check data list item 28: Cylinder 1, 4 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, Cylinder 1, 4 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.
Q: Is the specification normal?
YES : Go to Step 5.
NO : Refer to DTC P0171 -System too Lean (cylinder 1, 4), P0171 DTC P0172 -System too Rich (cylinder 1, 4). P0172
STEP 5. Using scan tool MB991958, check data list item 29: Cylinder 2, 3 Short-Term Fuel Trim.
1. Start the engine and run at idle.
2. Set scan tool MB991958 to the data reading mode for item 29, Cylinder 2, 3 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.
Q: Is the specification normal?
YES : Go to Step 6.
NO : Refer to DTC P0174 -System too Lean (cylinder 2, 3), P0174 DTC P0175 -System too Rich (cylinder 2, 3). P0175
STEP 6. Check the each ignition coil spark.
1. Remove the spark plug and connect to the ignition coil.
2. 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.
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 32 -Ignition Circuit System. Inspection Procedure 32
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.
a. Check for skipped timing belt teeth.
b. Check compression.
c. EGR valve failed.
Q: Are there any abnormalities?
YES : Repair or replace 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 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 or the PCM. When the ECM or the PCM is replaced, register the encrypted code. Refer to chassis electrical, Encrypted Code Registration Criteria Table. Then go to Step 10.
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 10. 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.