P0300
The content of this article reflects the changes identified in TSB - 10-13-007.Random Misfire Circuit
- Refer to, DTC P0201 - P0204 Injector Circuit Malfunction.
CIRCUIT OPERATION
- Refer to, DTC P0201 - P0204 Injector Circuit Malfunction.
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 500 and 6,000 r/min.
- 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 volt/10 ms to +0.059 volt/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:)
- 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.
- PCM failed.
DIAGNOSIS
Required Special Tools
- MB991502: Scan Tool (MUT-II)
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 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 the "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).
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).
- The fuel trim should be between -12.5 and +12.5 when the load 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, DTC P0172 - System too Rich.
STEP 3. Using scan tool MB991502, check data list item 82: Short-Term Fuel Compensation (trim).
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).
- The fuel trim should be between -25 and +25 when the load 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 P0171 - System too Lean, DTC P0172 - System too Rich.
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.
1. Check that the plug is not burned, that the insulator plug is not damaged, and that the seizure state is good.
2. If cleaning is required due to carbon deposits, etc., clean using a plug cleaner or wire brush, etc.
3. Check the plug gap using a plug gap gauge, and adjust if not within the standard value.
Standard value: 1.0 - 1.1 mm (0.039 - 0.043 inch)
Q: Is the spark plug in good condition?
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 19 kohm.
Q: Is the resistance normal?
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 terminal 1 and 2.
Standard value: 13 - 16 ohm [at 20 °C (68 °F)]
Q: Is the resistance standard value?
YES: Go to Step 8.
NO: Replace the faulty injector. Then go to Step 13.
STEP 8. Check connector B-17, B-18, B-20, B-22 at injector 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-121 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.
STEP 10. Check for harness damage between injector connector and ECM connector
a. Check the harness wire between injector connector B-22 terminal 2 and ECM connector C-121 terminal 1
b. Check the harness wire between injector connector B-20 terminal 2 and ECM connector C-121 terminal 14
c. Check the harness wire between injector connector B-18 terminal 2 and ECM connector C-121 terminal 2
d. Check the harness wire between injector connector B-17 terminal 2 and ECM connector C-121 terminal 15
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, Procedure 6 Other Monitor.
3. Check the diagnostic trouble code (DTC).
Q: Is the DTC P0300 output?
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 Procedure 6 - Other Monitor.
2. Check the diagnostic trouble code (DTC).
Q: Is the DTC P0300 output?
YES: Retry the troubleshooting.
NO: The inspection is complete.