P0300

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 and sudden acceleration/deceleration.
- The throttle deviation is -0.6 V/25 ms to +0.6 V/10 ms.
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

- 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 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:)

- 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

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.

Procedures.

Q. Is the spark plug normal?

YES Refer to INSPECTION PROCEDURE 31 - 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 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 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 or the PCM. When the ECM or the PCM is replaced, register the encrypted code. Encrypted Code Registration Criteria Table.
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.