Part One
1UR-FE ENGINE CONTROL: SFI SYSTEM: P0300-P0308: Random / Multiple Cylinder Misfire Detected
P0308 - Cylinder 8 Misfire Detected
DESCRIPTION
When the engine misfires, high concentrations of hydrocarbons (HC) enter the exhaust gas. Extremely high HC concentration levels can cause increases in exhaust emission levels. High concentrations of HC can also cause increases in the Three-Way Catalytic Converter (TWC) temperature, which may cause damage to the TWC. To prevent these increases in emissions and to limit the possibility of thermal damage, the ECM monitors the misfire rate. When the temperature of the TWC reaches the point of thermal degradation, the MIL blinks. To monitor misfires, the ECM uses both the Camshaft Position (CMP) sensor and the Crankshaft Position (CKP) sensor. The CMP sensor is used to identify any misfiring cylinders and the CKP sensor is used to measure variations in the crankshaft rotation speed. Misfires are counted as when the crankshaft rotation speed variations exceed predetermined thresholds.
If the misfire rate exceeds the threshold level, the ECM illuminates the MIL and stores a DTC.
When multiple DTCs for misfiring cylinders are stored, but DTC P0300 is not stored, it indicates that misfires have been detected in different cylinders at different times. DTC P0300 is only stored when several misfiring cylinders are detected at the same time.
MONITOR DESCRIPTION
The ECM illuminates the MIL and stores a DTC when either one of the following conditions, which could cause emission deterioration, is detected (2 trip detection logic).
* Within the first 1000 crankshaft revolutions of the engine starting, an excessive misfiring rate (approximately 20 to 50 misfires per 1000 crankshaft revolutions) occurs once.
* An excessive misfiring rate (approximately 20 to 50 misfires per 1000 crankshaft revolutions) occurs a total of 4 times.
The ECM flashes the MIL and stores a DTC when either one of the following conditions, which could cause Three-Way Catalytic Converter (TWC) damage, is detected (2 trip detection logic).
* At a high engine rpm, a sufficient amount of misfires to damage the catalyst occurring within 200 crankshaft revolutions is detected once.
* At a normal engine rpm, a sufficient amount of misfires to damage the catalyst occurring within 200 crankshaft revolutions is detected 3 times.
HINT
If a catalyst damage misfire occurs, the ECM informs the driver by flashing the MIL.
Misfire Monitor for Mexico Models
The ECM illuminates the MIL and sets a DTC when either one of the following conditions, which could cause emission deterioration, is detected (2 trip detection logic).
* Within the first 1000 crankshaft revolutions of the engine starting, an excessive misfiring rate (approximately 1000 misfires per 1000 crankshaft revolutions) occurs once.
* An excessive misfiring rate (approximately 500 misfires per 1000 crankshaft revolutions) occurs a total of 4 times.
The ECM flashes the MIL and sets a DTC when the following condition, which could cause Three-Way Catalytic Converter (TWC) damage, is detected (2 trip detection logic).
* A sufficient amount of misfires to damage the catalyst occurring within 200 crankshaft revolutions is detected 3 times.
MONITOR STRATEGY
TYPICAL ENABLING CONDITIONS
Misfire
Monitor Period of Emission-Related-Misfire
Monitor Period of Catalyst-Damaged-Misfire (MIL Blinks)
FOR MEXICO MODELS:
Misfire: for Mexico models
Monitor period of emission-related-misfire: for Mexico models
Monitor period of catalyst-damaged-misfire (MIL blinks): for Mexico models
TYPICAL MALFUNCTION THRESHOLDS
Monitor Period of Emission-Related-Misfire
Monitor Period of Catalyst-Damaged-Misfire (MIL Blinks)
FOR MEXICO MODELS:
Monitor period of emission-related-misfire: for Mexico models
Monitor period of catalyst-damaged-misfire (MIL blinks): for Mexico models
MONITOR RESULT
Refer to Checking Monitor Status Mode 6 Data.
WIRING DIAGRAM
CONFIRMATION DRIVING PATTERN
1. Connect the Techstream to the DLC3.
2. Turn the ignition switch to ON.
3. Turn the Techstream on.
4. Record the DTC(s) and freeze frame data.
5. Clear DTCs (even if no DTCs are stored, perform the clear DTC operation).
6. Using the Techstream, switch the ECM from normal mode to check mode Check Mode Procedure.
7. Read the misfire counts of each cylinder (cylinder No. 1 to No. 8) with the engine idling. If any misfire count is displayed, skip the following confirmation driving pattern.
8. Drive the vehicle several times with the conditions, such as engine rpm and engine load, as shown in Misfire RPM and Misfire Load in the freeze frame data.
HINT
In order to store misfire DTCs, it is necessary to operate the vehicle for the period of time shown in the table below, with the engine speed and engine load the same as Misfire RPM and Misfire Load in the freeze frame data.
9. Check whether misfires have occurred by checking DTCs and freeze frame data.
HINT
Do not turn the ignition switch off until the stored DTC(s) and freeze frame data have been recorded. When the ECM returns to normal mode (default), the stored DTC(s), freeze frame data and other data will be cleared.
10. Record the DTC(s), freeze frame data and misfire counts.
11. Turn the ignition switch off and wait for at least 5 seconds.
12. Clear DTCs (even if no DTCs are stored, perform the clear DTC operation).
INSPECTION PROCEDURE
HINT
- If any DTCs other than misfire DTCs are output, troubleshoot those DTCs first.
- Read freeze frame data using the Techstream. Freeze frame data records the engine condition when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data from the time the malfunction occurred.
- If the misfire does not recur when the vehicle is brought to the workshop, reproduce the conditions stored in the freeze frame data.
- If the misfire still cannot be reproduced even though the conditions stored in the freeze frame data have been duplicated, one of the following factors may be a cause of the problem:
(1) The fuel level is low.
(2) Improper fuel is used.
(3) The spark plugs are dirty.
- After finishing repairs, check that no misfires occur in each cylinder (cylinder No. 1, No. 2, No. 3, No. 4, No. 5, No. 6, No. 7 and No. 8).
- Be sure to confirm that no misfiring cylinder DTCs are stored again by conducting the confirmation driving pattern after the repairs.
- For 6 and 8 cylinder engines, the ECM intentionally does not store the specific misfiring cylinder DTCs at high engine RPM. If misfires only occur during high engine RPM driving, only DTC P0300 is stored.
In the event of DTC P0300 being present, perform the following operations:
(1) Clear the DTC DTC Check / Clear.
(2) Start the engine and conduct the confirmation driving pattern.
(3) Read the misfiring rates of each cylinder or DTC(s) using the Techstream.
(4) Repair the cylinder(s) that has a high misfiring rate or is indicated by the DTC.
(5) After finishing repairs, conduct the confirmation driving pattern again, in order to verify that DTC P0300 is not stored.
- When either Short FT #1, Long FT #1, Short FT #2 or Long FT #2 in the freeze frame data is outside the range of +/-20%, the air-fuel ratio may be rich (-20% or less) or lean (+20% or more).
- When Coolant Temp in the freeze frame data is less than 75°C (167°F), the misfires occurred only while warming up the engine.
- An extremely imbalanced drive wheel, which causes body vibration, may cause misfire DTCs to be detected.
PROCEDURE
1. CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO MISFIRE CODES)
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch to ON.
(c) Turn the Techstream on.
(d) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
(e) Read DTCs.
Result
HINT
If any DTCs other than P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307 and P0308 are output, troubleshoot those DTCs first.
B -- GO TO DTC CHART Engine Control System - SFI System
A -- Continue to next step.
2. CHECK PCV HOSE CONNECTIONS
(a) Check the PCV hose connections.
OK:
PCV hose is connected correctly and is not damaged.
NG -- REPAIR OR REPLACE PCV HOSE Removal
OK -- Continue to next step.
3. READ VALUE USING TECHSTREAM (MISFIRE RPM AND MISFIRE LOAD)
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch to ON.
(c) Turn the Techstream on.
(d) Enter the following menus: Powertrain / Engine and ECT / Data List / All Data / Misfire RPM and Misfire Load.
(e) Read and note the Misfire RPM and Misfire Load values.
HINT
The Misfire RPM and Misfire Load values indicate the vehicle conditions under which the misfire occurred.
NEXT -- Continue to next step.
4. READ VALUE USING TECHSTREAM
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch to ON.
(c) Turn the Techstream on.
(d) Enter the following menus: Powertrain / Engine and ECT / Data List / Catalyst OT MF F/C.
(e) Read the value displayed on the Techstream.
Result
B -- READ VALUE USING TECHSTREAM (MISFIRE COUNT)
A -- Continue to next step.
5. PERFORM ACTIVE TEST USING TECHSTREAM
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch to ON.
(c) Turn the Techstream on.
(d) Enter the following menus: Powertrain / Engine and ECT / Active Test / Prohibit the Catalyst OT Misfire prevent F/C.
(e) Perform the Active Test.
NOTICE:
When performing the Active Test, make sure the vehicle is stopped and either idling or being revved within 3000 rpm.
NEXT -- Continue to next step.
6. READ VALUE USING TECHSTREAM (MISFIRE COUNT)
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch to ON.
(c) Turn the Techstream on.
(d) Clear DTCs DTC Check / Clear.
(e) Enter the following menus: Powertrain / Engine and ECT / Data List / All Data / Cylinder #1 Misfire Rate, #2, #3, #4, #5, #6, #7 and #8.
(f) Allow the engine to idle.
(g) Read each value for CYL #1 to #8 (Cylinder #1 Misfire Rate to #8) displayed on the Techstream. If no misfire counts occur in any cylinders, perform the following procedures:
(1) Move the shift lever to D.
(2) Check CYL #1 to #8 (Cylinder #1 Misfire Rate to #8).
(3) If misfire counts are still not displayed, perform procedure "A" and "B", and then check the misfire counts again.
Procedure A: Drive the vehicle with the Misfire RPM and Misfire Load noted in the "Read value using Techstream (Misfire RPM and Misfire Load)" procedures above.
Procedure B: Read CYL #1 to #8 (Cylinder #1 Misfire Rate to #8) or DTCs displayed on the Techstream.
Result
HINT
- If it is difficult to reproduce misfires for each cylinder, check the Data List item called Misfire Margin. Try to find vehicle driving conditions that lower the Misfire Margin value. Values above 30% are considered normal.
- If the freeze frame data's record of the ECT is below 75°C (167°F), the misfire may be detected only when the engine is cold.
- If the freeze frame data's record of the Engine Run Time is below 120 seconds, the misfire may be detected immediately after the engine is started.
B -- CHECK AIR INDUCTION SYSTEM
A -- Continue to next step.