Troubleshooting
P0300 - Random/Multiple Cylinder Misfire DetectedCIRCUIT DESCRIPTION
DTC Detecting Condition:
Misfire: The ECM uses the crankshaft position sensor and camshaft position sensor to monitor changes in the crankshaft rotation of each cylinder.
The ECM counts the number of times from the engine speed change rate, indicating that misfire has occurred. And when the misfire rate equals to or exceeds the count, indicating that the engine condition has deteriorated, the MIL lights up.
If the misfire rate is high enough and the driving conditions causes the catalyst to overheat, the MIL blinks when the misfire occurs.
HINT: When the 2 or more codes for a misfiring cylinder are recorded repeatedly but no random misfire code is recorded, it is indicated that the misfires were detected and recorded at different times.
Wiring Diagram:
CONFIRMATION DRIVING PATTERN
a. Connect the TOYOTA hand-held tester or OBDII scan tool to the DLC3.
b. Record the DTC and freeze frame data.
c. Use the TOYOTA hand-held tester to set to the check mode.
d. 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 TOYOTA hand-held tester, turn the ignition switch OFF after the symptom is simulated once. Then repeat the simulation process again.
HINT: In order to memorize the DTC of the misfire, it is necessary to drive around MISFIRE RPM, MISFIRE LOAD in the following data list.
e. Check whether there is misfire or not by monitoring the DTC and the freeze frame data, and then, record them.
f. Turn the ignition switch OFF and wait at least 5 seconds.
Step 1:
Step 2 - 4:
Step 5 - 9:
INSPECTION PROCEDURE
HINT:
- If the other DTCs besides misfire are memorized simultaneously, first perform the troubleshooting for them.
- Read freeze frame data using the TOYOTA hand-held tester or OBDII scan tool, as freeze frame data records the engine conditions when the malfunction is detected. When troubleshooting, it is useful for determining whether the vehicle was running or stopped, the engine was warmed up or not, the air-fuel ratio was lean or rich, etc. at the time of the malfunction.
- If the misfire is not occurred when the vehicle is brought to the workshop, it can be confirmed by reproducing the condition of the freeze frame data. After finishing the repair, confirm that there is no misfire (See the confirmation driving pattern).
- When either of SHORT FT #1, LONG FT #1, SHORT FT #2 or LONG FT #2 in the freeze frame data is over the range of ± 20%, there is a possibility that the air-fuel ratio is inclining either to "RICH" (-20% or less) or "LEAN" (+20% or more).
- When COOLANT TEMP in the freeze frame data is less than 80 °C (176 °F), there is a possibility of misfire only during warming up.
- In case that the misfire cannot be reproduced, this may be because of the driving with the shortage of fuel, the use of improper fuel, a stain of ignition plug and etc.