P0305
DTC P0305 CYLINDER 5 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 can 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.
If the misfiring rate exceeds the threshold value and could cause emissions deterioration, the ECM illuminates the MIL.
HINT: When several 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 the oscilloscope.
With the engine idling, check the waveform between terminals #10 to #60 and E01 of the ECM connectors.
HINT: The correct waveform is as shown.
MONITOR DESCRIPTION
Monitor Strategy:
Typical Enabling Conditions:
Typical Malfunction Thresholds:
The ECM illuminates the MIL (2 trip detection logic) if:
- The misfiring rate exceeds a threshold value and could cause emissions 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 1 time.
- 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 1 time.
- 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 continuously).
Wiring Diagram:
CONFIRMATION DRIVING PATTERN
a. Connect the hand-held tester to the DLC3.
b. Record DTC and the freeze frame data.
c. Set the hand-held tester to 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 to 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. Take care not to turn the ignition switch to OFF. This will switch the diagnosis system from check mode, to normal mode and all DTCs, freeze frame data and other data will be erased.
f. Check if there is misfire, DTC and the freeze frame data. Record the DTCs, freeze frame data and misfire counter data.
g. Turn the ignition switch to OFF and wait at least 5 seconds.
Step 1 - 3:
Step 4 - 5:
Step 5 (Contd.) - 7:
Step 7 (Count.) - 8:
Step 9 - 10:
Step 10 (Contd.) - 13:
Step 14 - 17:
Step 18 - 19:
INSPECTION PROCEDURE
HINT:
- If DTCs besides misfire DTCs are memorized simultaneously, troubleshoot the non-misfire DTCs first.
- 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).
- 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 hand-held 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.
- When one of SHORT FT #1, LONG FT #1, SHORT FT #2 and LONG FT #2 in the freeze frame data is outside the range of ±20 %, there is a possibility that the air-fuel ratio is becoming 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 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.
CHECK FOR INTERMITTENT PROBLEMS
HINT:
Hand-held tester only:
Inspect the vehicle's ECM using check mode. Intermittent problems are easier to detect when the ECM is in check mode with a hand-held tester. In check mode, the ECM uses 1 trip detection logic, which has a higher sensitivity to malfunctions than normal mode (default) using 2 trip detection logic.
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.