Troubleshooting
P0303 - Cylinder 3 Misfire DetectedCIRCUIT DESCRIPTION
DTC Detection 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 of indicating that misfire has occurred, by using the engine speed change rate. And when the misfire rate equals to or exceeds the count of indicating that the engine condition has deteriorated, the MIL lights up.
If the misfire rate is very high and the driving conditions will cause the catalyst to overheat, the MIL shows the occurrence of misfire by blinking.
HINT: When codes for a misfiring cylinder are recorded repeatedly but no random misfire code is recorded, it indicates that the misfires were detected and recorded at different times.
Wiring Diagram:
CONFIRMATION DRIVING PATTERN
a. Connect the TOYOTA hand-held tester or OBD II scan tool to the DLC3.
b. Record 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 misfire, it is necessary to drive around MISFIRE RPM, MISFIRE LOAD for the following period of time in the data list.
e. Check whether there is misfire or not by monitoring DTC and freeze frame data. After that, record them.
f. Turn the ignition switch OFF and wait at least 5 seconds.
Step 1:
Step 2:
Steps 3 - 4:
Steps 5 - 7:
INSPECTION PROCEDURE
HINT:
- In case the DTCs besides misfire is memorized simultaneously, first perform the troubleshooting for them.
- Read freeze frame data using TOYOTA hand-held tester or OBD II scan tool, as freeze frame data records the engine conditions when a 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 does not occur when the vehicle is brought to a workshop, misfire can be confirmed by reproducing the condition of freeze frame data. Also after finishing the repair, confirm that there is no misfire (See 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 TEMPERATURE in the freeze frame data is less than 80 °C (176 °F), there is a possibility of misfire only during warming up (the engine).
- In case that misfire cannot be reproduced, the reason may be because of driving with lack of fuel, use of improper fuel, a stain of the ignition plug, and etc.