P0300
Random Misfire Circuit- Refer to DTC P0201, P0203, P0205 - Injector Circuit.
- Refer to DTC P0202, P0204, P0206 - Injector Circuit.
CIRCUIT OPERATION
- Refer to DTC P0201, P0203, P0205 - Injector Circuit.
- Refer to DTC P0202, P0204, P0206 - Injector Circuit.
TECHNICAL DESCRIPTION
- If a misfire occurs while the engine is running, the engine speed changes for an instant.
- The ECM
DTC SET CONDITIONS
Check Conditions
- Engine speed is between 440 and 6,000 rpm.
- Engine coolant temperature is higher than -10 °C (14 °F).
- Intake air temperature is higher than -10 °C (14 °F).
- Barometric pressure is higher than 76 kPa (11 psi).
- 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 -0.059 v/10 ms to +0.059 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 950 °C (1742 °F).
or
- Misfire has occurred in 20 or more of the last 1,000 revolutions (corresponding to 1.5 times the limit of emission standard).
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.
DIAGNOSIS
Required Special Tool:
- MB991502: Scan Tool (MUT-II)
STEP 1. Using scan tool MB991502, check data list item 22: Crankshaft Position Sensor.
CAUTION
To prevent damage to scan tool MB991502, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.
1. Connect scan tool MB991502 to the data link connector.
2. Start the engine and run at idle.
3. Set scan tool MB991502 to the data reading mode for item 22, 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 "LOCK" (OFF) position.
Q: Is the sensor operating properly?
YES: Go to Step 2.
NO: Refer to DTC P0335 - Crankshaft Position Sensor Circuit Malfunction.
STEP 2. Using scan tool MB991502, check data list item 81: Long-Term Fuel Compensation (trim) Bank 1.
1. Start the engine and run at idle.
2. Set scan tool MB991502 to the data reading mode for item 81, Long-Term Fuel Compensation (trim) Bank 1.
- The fuel trim should be between -12.5 and +12.5 when the load is 2,500 rpm (during closed loop) after the engine is warmed.
3. Turn the ignition switch to "LOCK" (OFF) position.
Q: Is the specification normal?
YES: Go to Step 3.
NO: Refer to DTC P0171 - System too Lean (bank 1), DTC P0172 - System too Rich (bank 1), DTC P0174 - System too Lean (bank 2), DTC P0175 - System too Rich (bank 2).
STEP 3. Using scan tool MB991502, check data list item 82: Short-Term Fuel Compensation (trim) Bank 1.
1. Start the engine and run at idle.
2. Set scan tool MB991502 to the data reading mode for item 82, Short-Term Fuel Compensation (trim) Bank 1.
- The fuel trim should be between -25 and +25 when the load is 2,500 rpm (during closed loop) after the engine is warmed.
3. Turn the ignition switch to "LOCK" (OFF) position.
Q: Is the specification normal?
YES: Go to Step 4.
NO: Refer to DTC P0171-System too Lean (bank 1), DTC P0172-System too Rich (bank 1), DTC P0174 - System too Lean (bank 2), DTC P0175 - System too Rich (bank 2).
STEP 4. Check the ignition coil spark.
1. Check each ignition coil spark.
2. Remove the intake manifold.
3. Remove the spark plug and connect to the spark plug cable.
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 5.
STEP 5. Check the spark plugs.
CAUTION
Do not attempt to adjust the gap of the platinum plug. Cleaning of the platinum plug may result in damage to the platinum tips. Therefore, if carbon deposits must be removed, use a plug cleaner and complete cleaning within 20 seconds to protect the electrode. Do not use a wire brush.
1. Check the plug gap and replace if the limit is exceeded.
Standard value: 1.0 - 1.1 mm (0.039 - 0.043 inch)
Limit: 1.3 mm (0.051 inch)
Q: Is the plug gap at the standard value?
YES: Go to Step 6.
NO: Replace the faulty spark plug. Then go to Step 13.
STEP 6. Check the spark plug cable.
1. Check the cap and coating for cracks.
2. Measure the resistance.
Limit: maximum 22 kohms
Q: Is the measured resistance less than 22 kohms?
YES: Refer to INSPECTION PROCEDURE 33 Ignition Circuit System.
NO: Replace the faulty spark plug cable. Then go to Step 13.
STEP 7. Check the injector.
1. Disconnect the injector connector.
2. Measure the resistance between each injector side connector terminals No.1 and No.2.
Standard value: 13 - 16 ohms @ 20 °C (68 °F)
Q: Is the resistance between 13 and 16 ohms @ 20 °C (68 °F)?
YES: Go to Step 8.
NO: Replace the faulty injector. Then go to Step 13.
STEP 8. Check connectors B-01, B-02, B-05, B-06, B-25, B-26 at injector and connector B-118 at injector intermediate connector for damage.
Q: Is the connector in good condition?
YES: Go to Step 9.
NO: Repair or replace the faulty injector. Refer to Harness Connector Inspection. Then go to Step 13.
STEP 9. Check connector C-111 at ECM
Q: Is the connector in good condition?
YES: Go to Step 10.
NO: Repair or replace it. Refer to Harness Connector Inspection. Then go to Step 13.
Connectors:
STEP 10. Check for harness damage between injector connector and ECM connector
a. Check the harness wire between injector connector B-01 (terminal No.2) and ECM connector C-111 (terminal No.1)
b. Check the harness wire between injector connector B-02 (terminal No.2) and ECM connector C-111 (terminal No.9)
c. Check the harness wire between injector connector B-05 (terminal No.2) and ECM connector C-111 (terminal No. 24)
d. Check the harness wire between injector connector B-06 (terminal No.2) and ECM connector C-111 (terminal No.2)
e. Check the harness wire between injector connector B-26 (terminal No.2) and ECM connector C-111 (terminal No. 10)
f. Check the harness wire between injector connector B-25 (terminal No.2) and ECM connector C-111 (terminal No. 25)
Q: Is the harness wire in good condition?
YES: Go to Step 11.
NO: Repair it. Then go to Step 13.
STEP 11. 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: Go to Step 12.
NO: Repair or replace it. Then go to Step 13.
STEP 12. Replace the injector.
1. Replace the injector.
2. Carry out a test drive with the drive cycle pattern. Refer to Trouble Code Diagnosis - OBD-III Drive Cycle - Procedure 6 - Other Monitor.
3. Check the diagnostic trouble code (DTC).
Q: Is DTC P0300 set?
YES: Replace the ECM or PCM. Then go to Step 13.
NO: The inspection is complete.
STEP 13. Test the OBD-II drive cycle.
1. Carry out a test drive with the drive cycle pattern. Refer to Trouble Code Diagnosis - OBD-II Drive Cycle Procedure 6 - Other Monitor.
2. Check the diagnostic trouble code (DTC).
Q: Is DTC P0300 set?
YES: Retry the troubleshooting.
NO: The inspection is complete.