P0300
DTC P0300 Random / Multiple Cylinder Misfire DetectedDTC P0301 Cylinder 1 Misfire Detected
DTC P0302 Cylinder 2 Misfire Detected
DTC P0303 Cylinder 3 Misfire Detected
DTC P0304 Cylinder 4 Misfire Detected
DESCRIPTION
DTC Detection Condition:
When a misfire occurs in the engine, hydrocarbons (HC) are output in high concentrations. If this HC concentration is high enough, there could be an increase in exhaust emissions levels. High concentrations of HC can also cause the temperature of the catalyst to increase, possibly damaging the catalyst. To prevent increases in emissions and limit the possibility of thermal damage, the ECM monitors the misfire rate. When the temperature of the catalyst reaches a point of thermal degradation, the ECM will blink the MIL. For monitoring a misfire, the ECM uses both the camshaft position sensor and the crankshaft position sensor. The camshaft position sensor is used to identify misfiring cylinders and the crankshaft position sensor is used to measure variations in the crankshaft rotation speed. A misfire is counted when crankshaft rotation speed variations exceed threshold values.
If the misfiring rate exceeds the threshold value and could cause emission deterioration, the ECM illuminates the MIL.
HINT: When several codes for a misfiring cylinder are recorded repeatedly but no random misfire code is recorded, the misfires have been detected and recorded at different times.
MONITOR DESCRIPTION
Monitor Strategy:
Typical Enabling Conditions (Part 1):
Typical Enabling Conditions (Part 2):
Typical Malfunction Thresholds:
The ECM illuminates the MIL (2 trip detection logic) if:
- The misfiring rate exceeds a threshold value and could cause emission deterioration.
- During the first 1,000 engine revolutions after the engine starts, an excessive misfire rate (approximately 20 to 50 misfire per 1,000 engine revolutions) occurs once.
- After the first 1,000 engine revolutions after the engine starts, an excessive misfire rate (approximately 20 to 50 misfire per 1,000 engine revolutions) occurs 4 times.
The ECM blinks the MIL (MIL blinks immediately) if:
- Within 200 engine revolutions at a high rpm, the threshold for "percent of misfire causing catalyst damage" is reached once.
- Within 200 engine revolutions at a normal rpm, the threshold for "percent of misfire causing catalyst damage" is reached 3 times. (for the 2nd trip, reaching the threshold once will cause the MIL to flash)
CONFIRMATION DRIVING PATTERN
1. Connect the intelligent tester to the DLC3.
2. Record the DTCs, freeze frame data and misfire counter data.
3. Set the intelligent tester to check mode.
4. Read the value on the misfire counter for each cylinder when idling. If the value is displayed on the misfire counter, skip the following procedure of confirmation driving.
5. Drive the vehicle several times with the engine speed, load and its surrounding range shown with ENGINE SPD, CALC LOAD in the freeze frame data or MISFIRE RPM, MISFIRE LOAD in the DATA LIST.
If you have no intelligent tester, turn the ignition switch OFF after the symptom is simulated once. Then repeat the simulation process again.
HINT: In order to memorize the misfire DTC, it is necessary to drive with MISFIRE RPM, MISFIRE LOAD in the DATA LIST for the period of time in the chart given. Take care not to turn the ignition switch OFF.
Turning the ignition switch OFF switches the diagnosis system from check mode to normal mode and all DTCs, freeze frame data and other data are erased.
6. Check if there is misfire, DTC and the freeze frame data. Record the DTCs, freeze frame data and misfire counter data.
7. Turn the ignition switch OFF and wait for at least 5 seconds.
HINT:
- If DTCs besides misfire DTCs are memorized simultaneously, troubleshoot the non-misfire DTCs first.
- Read freeze frame data using the intelligent tester or the OBD II scan tool. The ECM records vehicle and driving condition information as freeze data the moment a DTC is stored. When troubleshooting, freeze frame data can help determine if the vehicle was running or stopped, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data from the time the malfunction occurred.
- If the misfire does not occur when the vehicle is brought to the workshop, the misfire can be confirmed by reproducing the condition of the freeze frame data. Also, after finishing the repair, confirm that there is no misfire (see confirmation driving pattern).
- On 6 and 8 cylinder engines, cylinder specific misfire fault codes are disabled at high engine speeds. If the misfire starts in a high engine speed area or the misfire occurs only in a high engine speed area, only the general fault code P0300 will be stored. When only a general misfire fault code like P0300 is stored:
1. Erase the general misfire fault code from the ECM using the intelligent tester or OBD II scan tool.
2. Start the engine and drive the confirmation pattern.
3. Read the value of the misfire ratio for each cylinder. Or read the DTC.
4. Perform repairs on the cylinder that has a high misfire ratio. Or repair the cylinder indicated by the DTC.
5. After finishing repairs, drive the confirmation pattern again and confirm that no misfire occurs.
- When either of SHORT FT #1, LONG FT #1 in the freeze frame data is over the range of ±20%, there is a possibility that the air-fuel ratio is becoming to RICH (-20% or less) or LEAN (+20% or more).
- When COOLANT TEMP in the freeze frame data is less than 80 degree C (176 degree F), there is a possibility of misfire only during engine warm-up.
- If the misfire cannot be reproduced, the following reasons may apply: 1) the vehicle has low fuel, 2) improper fuel is being used, and 3)the ignition plug is contaminated.
- Be sure to check the value on the misfire counter after the repair.
Wiring Diagram:
Wiring Diagram:
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Step 19:
INSPECTION PROCEDURE