P0302
DTC P0302 CYLINDER 2 MISFIRE DETECTEDCIRCUIT DESCRIPTION
DTC Detection Condition:
When a misfire occurs in the engine, hydrocarbons (HC) enter the exhaust in high concentrations. If this HC concentration is high enough, there could be an increase in exhaust emissions levels. High concentrations of HC passing through the catalyst also cause to temperature of the catalyst to increase, possibly damaging the catalyst. To prevent this increase 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 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. The misfire counter increments when crankshaft rotation speed variations exceed threshold values.
The ECM illuminates the MIL if the misfiring rate exceeds a threshold value and could cause emissions deterioration.
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.
Reference: INSPECTION USING OSCILLOSCOPE
With the engine idling, check the waveform between terminals #10 to #40 and E01 of the ECM connectors.
HINT: The correct waveform is as shown.
MONITOR DESCRIPTION
Monitor Descrition:
Monitor Strategy:
Typical Enabling Conditions:
Typical Malfunction Thresholds:
The ECM illuminates the MIL if the misfiring rate exceeds a threshold value and could cause emissions deterioration.
The ECM will illuminate the MIL when the percent misfire exceeds the specified limit per 1,000 engine revolutions. One occurrence of excessive misfire during engine start will set the MIL. Four occurrences are required to set the MIL 1,000 revolutions after engine start. (2 trip detection logic)
The MIL blinks when "percent misfire causing catalyst damage" per 200 revolution is met 3 times (1 time if the engine rpm is in high speed range). (MIL blinks immediately)
Wiring Diagram:
Wiring Diagram:
CONFIRMATION DRIVING PATTERN
a. Connect the hand-held tester or the OBD II scan tool to the DLC3.
b. Record DTC and the freeze frame data.
c. Use the hand-held tester to set the check mode.
d. 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.
e. 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 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 in the DATA LIST for the following period of time. Take care not to turn the ignition switch OFF. Turning the ignition switch OFF switches the diagnosis system from check mode to normal mode. So all DTCs, etc, are erased.
f. Check whether there is misfire or not by monitoring DTC and the freeze frame data. After that, record them.
g. Turn the ignition switch OFF and wait for at least 5 seconds.
Step 1 - 4:
Step (4 Continued - 5):
Step 6 - 7:
Step (7 Continued - 8):
Step 9 - 10:
Step (10 Continued - 15):
Step 16 - 17:
Step 18 - 19:
INSPECTION PROCEDURE
HINT:
- If DTCs besides misfire are memorized simultaneously, first perform the troubleshooting for them.
- Read freeze frame data using the hand-held tester or the OBD II scan tool. 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 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).
- When either of SHORT FT #1 or LONG FT #1 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 engine warm-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.
- Be sure to check the value on the misfire counter after the repair.
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 faults is increased. This makes it easier to detect intermittent problems.
a. Clear the DTCs.
b. Set the check mode.
c. Perform a simulation test.
d. Check the connector and terminal.
e. Wiggle the harness and connector.