Troubleshooting
DTC P0306 CYLINDER 6 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 for each cylinder.
The ECM counts the number of times that engine speed change rate indicates that misfire has occurred. 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 high enough and the driving conditions will cause the catalyst to overheat, the when misfiring occurs, the MIL blinks.
HINT: When codes for a misfiring cylinder are recorded repeatedly but no random misfire code is recorded, it indicates that the misfires have been detected and recorded at different times.
Wiring Diagram:
CONFIRMATION DRIVING PATTERN
a. Connect the OBD II scan tool or the hand-held tester to the DLC3.
b. Record the DTC and freeze frame data.
c. Use the hand-held tester to set to the check mode.
d. Drive the vehicle several times to see 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 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 data list shown.
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.
INSPECTION PROCEDURE
HINT:
- If DTCs besides misfire are memorized simultaneously, first perform the troubleshooting for them.
- Read freeze frame data using hand-held tester or the OBD II scan tool, as freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, this 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 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, misfiring cylinder identification is disabled at high engine speed and only an general misfire fault code P0300 is stored instead of a cylinder specific misfire fault code (i. e., P0301 - P0308). Under the following conditions, only P0300 code may be stored.
Misfire starts in the high engine speed area or Misfire occurs only in the high engine speed area. Therefore, when a general misfire fault code (i.e., P0300) is only stored, erase the DTCs after read freeze frame data with the hand-held tester or OBD II scan tool. Start the engine and drive the confirmation pattern (See the CONFIRMATION DRIVING PATTERN) and read the value of the misfire ratio for each cylinder (or DTC). Perform the repair correspond to the high misfire ratio cylinder (or the misfiring cylinder indicated by DTC). After completing the repair, confirm no misfire is occurring by driving the confirmation pattern.
- When any 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 occurs only during warming up.
- If the misfire cannot be reproduced, the reason may be because of the driving the vehicle with lack of fuel, the use of improper fuel, a stain on the ignition plug, etc.
Step 1 - 4:
Step 5 - 7:
Step 8 - 9:
Step 10 - 15:
Step 16 - 19:
Hand-held tester
Step 1:
Step 2 - 6:
Step 7 - 8:
Step 10 - 16:
OBD II scan tool (excluding hand-held tester)
CHECK FOR INTERMITTENT PROBLEMS
Hand-held tester only:
By putting the vehicle's ECM in the check mode, the 1 trip detection logic is possible instead of the 2 trip detection logic and the sensitivity to detect open circuits is increased. This makes it easier to detect intermittent problems.
1. Clear the DTCs.
2. Set the check mode.
3. Perform a simulation test.
4. Check the connector and terminal.
5. Handle the connector.