P0303
1GR-FE ENGINE CONTROL SYSTEM: SFI SYSTEM: P0300: Random / Multiple Cylinder Misfire Detected
DTC P0300 - Random / Multiple Cylinder Misfire Detected
DTC P0301 - Cylinder 1 Misfire Detected
DTC P0302 - Cylinder 2 Misfire Detected
DTC P0303 - Cylinder 3 Misfire Detected
DTC P0304 - Cylinder 4 Misfire Detected
DTC P0305 - Cylinder 5 Misfire Detected
DTC P0306 - Cylinder 6 Misfire Detected
DESCRIPTION
When the engine misfires, high concentrations of hydrocarbons (HC) enter the exhaust gas. Extremely high HC concentration levels can cause increase 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 this increase 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 ECM blinks the MIL. To monitor misfires, the ECM uses both the VVT 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 when the crankshaft rotation speed variations exceed predetermined thresholds.
If the misfire exceeds the threshold levels, and could cause emission deterioration, the ECM illuminates the MIL and sets a DTC.
HINT: When DTCs for misfiring cylinders are randomly set, but DTC P0300 is not set, it indicates that misfires have been detected in different cylinders at different times. DTC P0300 is only set when several misfiring cylinders are detected at the same time.
Reference: Inspection using an oscilloscope.
With the engine idling, check the waveform between terminals #10 to #60 and E1 of the ECM connectors.
HINT: The correct waveform is as shown.
MONITOR DESCRIPTION
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 20 to 50 misfires per 1000 crankshaft revolutions) occurs once.
- After the first 1000 crankshaft revolutions, an excessive misfiring rate (approximately 20 to 50 misfires per 1000 crankshaft revolutions) occurs 4 times in sequential crankshaft revolutions.
The ECM flashes the MIL and sets a DTC when either one of the following conditions, which could cause the Three-Way Catalytic Converter (TWC) damage, is detected (2 trip detection logic).
- In every 200 crankshaft revolutions at a high engine rpm, the threshold misfiring percentage is recorded once.
- In every 200 crankshaft revolutions at a normal engine rpm, the threshold misfiring percentage is recorded 3 times.
MONITOR STRATEGY
TYPICAL ENABLING CONDITIONS
Misfire:
Monitor period of emission-related-misfire:
Monitor period of catalyst-damaged-misfire (MIL blinks):
TYPICAL MALFUNCTION THRESHOLDS
Monitor period of emission-related-misfire:
Monitor period of catalyst-damage-misfire (MIL blinks):
MONITOR RESULT
Detailed information on Checking Monitor Status (Mode 6 Data).
WIRING DIAGRAM
CONFIRMATION DRIVING PATTERN
1. Connect the Techstream to the DLC3.
2. Turn the ignition switch ON.
3. Turn the tester ON.
4. Record the DTC(s) and freeze frame data.
5. Using the tester, switch the ECM from normal mode to check mode (Check Mode Procedure).
6. Read the misfire counts of each cylinder (Cylinder #1 Misfire Count to Cylinder #6 Misfire Count) with the engine in an idling condition. If any misfire count is displayed, skip the following confirmation driving pattern.
7. Drive the vehicle several times with the conditions, such as engine rpm and engine load, shown in Misfire RPM and Misfire Load in the Data List.
HINT: In order to store misfire DTCs, it is necessary to drive the vehicle for the period of time shown in the table below, with the Misfire RPM and Misfire Load in the Data List.
8. 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 erased.
9. Record the DTC(s), freeze frame data and misfire counts.
10. Turn the ignition switch OFF and wait for at least 5 seconds.
INSPECTION PROCEDURE
HINT:
- If any DTCs other than the misfire DTCs are output, troubleshoot those DTCs first.
- Read freeze frame data using the Techstream. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can be helpful in determining whether the vehicle was running or stopped, whether the engine was warmed up or not, whether the air/fuel ratio was lean or rich, as well as other data recorded at the time of a malfunction.
- 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 is considered to be a possible cause of the problem:
1. The fuel tank is low full.
2. Improper fuel is used.
3. The spark plugs have been contaminated.
4. The problem is complex.
- After finishing repairs, check the misfire counts of the cylinders (Cylinder #1 Misfire Count to Cylinder #6 Misfire Count).
- Be sure to confirm that no misfiring cylinder DTCs are set again by conducting the confirmation driving pattern, after repairs.
- For 6 and 8 cylinder engines, the ECM intentionally does not set the specific misfiring cylinder DTCs at high engine RPM. If misfires occur only in high engine RPM areas, only DTC P0300 is set.
If 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 tester.
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 set.
- When one of 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 the Coolant Temp in the freeze frame data is less than 75°C (167°F), the misfires have occurred only while warming up the engine.
- An extremely imbalanced drive wheel can cause body vibration, which may cause misfire DTC detection
PROCEDURE
1. CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO MISFIRE DTCS)
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch ON.
(c) Turn the tester 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 and P0306 are output, troubleshoot those DTCs first.
B -- GO TO DTC CHART
A -- Continue to next step.
2. READ VALUE USING TECHSTREAM (MISFIRE RPM AND MISFIRE LOAD)
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch ON and turn the tester ON.
(c) Enter the following menus: Powertrain / Engine and ECT / Data List / Misfire / Misfire RPM and Misfire Load.
(d) Read and note the Misfire RPM and Misfire Load (engine load) values.
HINT: The Misfire RPM and Misfire Load indicate the vehicle conditions under which the misfire occurred.
NEXT -- Continue to next step.
3. CHECK PCV HOSE CONNECTIONS
OK:
PCV hose is connected correctly and is not damaged.
NG -- REPAIR OR REPLACE PCV HOSE
OK -- Continue to next step.
4. CHECK MISFIRE COUNT (Cylinder #1 Misfire Count to #6)
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch ON.
(c) Turn the tester ON.
(d) Clear DTCs (DTC Check / Clear).
(e) Enter the following menus: Powertrain / Engine and ECT / Data List / Misfire / Cylinder #1 Misfire Count to #6.
(f) Allow the engine to idle.
(g) Read each value of Cylinder #1 Misfire Count to #6 displayed on the tester. If no misfire counts occur in any cylinders, perform the following operations:
(1) Shift the gear selector lever to the D position.
(2) Repeat steps (e) to (g) above.
(3) Check the Cylinder #1 Misfire Count to #6.
(4) If misfire counts are still not displayed, perform steps (h) and (i) and then check the misfire counts again.
(h) Drive the vehicle with the Misfire RPM and Misfire Load noted in step 2.
(i) Read the Cylinder #1 Misfire Count to #6 or DTCs displayed on the tester.
Result:
B -- CHECK AIR INDUCTION SYSTEM
A -- Continue to next step.
5. CHECK SPARK PLUG
(a) Remove the ignition coil and the spark plug of the misfiring cylinder.
(b) Measure the spark plug electrode gap.
Standard:
Between 1.0 mm and 1.1 mm (0.039 in. and 0.043 in.)
(c) Check the electrode for carbon deposits.
Recommended spark plug:
NOTE: If the electrode gap is larger than standard, replace the spark plug. Do not adjust the electrode gap.
(d) Reinstall the ignition coil and the spark plug.
NG -- REPLACE SPARK PLUG
OK -- Continue to next step.
6. CHECK SPARKS AND IGNITION
(a) Disconnect the injector connectors, in order to prevent the engine from starting.
(b) Install the spark plug to the ignition coil.
(c) Attach the spark plug assembly to the cylinder head cover.
(d) Crank the engine for less than 2 seconds and check the spark.
OK:
Sparks jump across electrode gap
(e) Reconnect the injector connectors.
NG -- CHANGE NORMAL SPARK PLUG AND CHECK SPARK OF MISFIRING CYLINDER
OK -- Continue to next step.
7. CHECK CYLINDER COMPRESSION PRESSURE OF MISFIRING CYLINDER
(a) Measure the cylinder compression pressure of the misfiring cylinder.
OK -- INSPECT ECM TERMINAL OF MISFIRING CYLINDER (#10, 20, #30, #40, #50 AND/OR #60 VOLTAGE)
NG -- REPAIR OR REPLACE MALFUNCTION PARTS
8. CHANGE NORMAL SPARK PLUG AND CHECK SPARK OF MISFIRING CYLINDER
(a) Change the installed spark plug to a spark plug that functions normally.
(b) Perform a spark test.
CAUTION: Always disconnect each injector connector.
NOTE: Do not crank the engine for more than 2 seconds.
(1) Install the spark plug to the ignition coil and connect the ignition coil connector.
(2) Disconnect the injector connector.
(3) Ground the spark plug.
(4) Check if sparks occur while the engine is being cranked.
OK:
Sparks jump across electrode gap.
NG -- REPLACE IGNITION COIL ASSEMBLY THEN CONFIRM THAT THERE IS NO MISFIRE
OK -- REPLACE SPARK PLUG
9. INSPECT ECM TERMINAL OF MISFIRING CYLINDER (#10, 20, #30, #40, #50 AND/OR #60 VOLTAGE)
(a) Turn the ignition switch ON.
(b) Measure the voltage between the terminals of the E6 and E4 ECM connectors.
Standard Voltage:
OK -- CHECK FUEL INJECTOR OF MISFIRING CYLINDER
NG -- Continue to next step.
10. CHECK HARNESS AND CONNECTOR (INJECTOR - ECM)
(a) Disconnect the injector connector (of the misfiring cylinder).
(b) Disconnect the E6 ECM connector.
(c) Turn the ignition switch ON.
(d) Measure the resistance and voltage between the injector and the ECM connector terminals.
Standard (Cylinder No. 1):
Standard (Cylinder No. 2):
Standard (Cylinder No. 3):
Standard (Cylinder No. 4):
Standard (Cylinder No. 5):
Standard (Cylinder No. 6):
(e) Reconnect the injector connector.
(f) Reconnect the ECM connector.
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.
11. CHECK FUEL INJECTOR OF MISFIRING CYLINDER
(a) Check the injector injection (whether fuel volume is high or low, and whether injection pattern is poor).
NG -- REPLACE FUEL INJECTOR ASSEMBLY
OK -- Continue to next step.
12. CHECK VALVE CLEARANCE OF MISFIRING CYLINDER
NG -- ADJUST VALVE CLEARANCE
OK -- Continue to next step.
13. CHECK AIR INDUCTION SYSTEM
(a) Check the air induction system for vacuum leakage.
OK:
No leakage from air induction system.
NG -- REPAIR OR REPLACE AIR INDUCTION SYSTEM
OK -- Continue to next step.
14. CHECK VALVE TIMING
(a) Remove the cylinder head cover.
(b) Turn the crankshaft pulley, and align its groove with the timing mark "0" of the timing chain cover.
(c) Check that the timing marks of the camshaft timing gears are aligned with the timing marks of the bearing cap as shown in the illustration.
If not, turn the crankshaft 1 revolution (360°) and align the marks as above.
OK:
Timing marks on camshaft timing gears are aligned as shown in illustration.
(d) Reinstall the cylinder head cover.
NG -- ADJUST VALVE TIMING
OK -- Continue to next step.
15. CHECK FUEL PRESSURE
(a) Check the fuel pressure (Testing and Inspection).
NG -- CHECK AND REPLACE FUEL PUMP, PRESSURE REGULATOR, FUEL PIPE LINE AND FILTER
OK -- Continue to next step.
16. READ VALUE USING TECHSTREAM (COOLANT TEMP)
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch ON.
(c) Turn the tester ON.
(d) Enter the following menus: Powertrain / Engine and ECT / All Data / Coolant Temp.
(e) Read the Coolant Temp twice, when the engine is both cold and warmed up.
Standard:
With cold engine: Same as ambient air temperature.
With warm engine: Between 80°C and 100°C (176°F and 212°F).
NG -- REPLACE ENGINE COOLANT TEMPERATURE SENSOR
OK -- Continue to next step.
17. READ VALUE USING TECHSTREAM (MAF)
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch ON.
(c) Turn the tester ON.
(d) Enter the following menus: Powertrain / Engine and ECT / All Data / Coolant Temp and MAF.
(e) Allow the engine to idle until the Coolant Temp reaches 75°C (167°F) or more.
(f) Read the MAF with the engine in an idling condition and at an engine speed of 2500 rpm.
Standard:
MAF while engine idling: Between 3.2 g/sec and 4.7 g/sec (shift position: N, A/C: OFF).
MAF at engine speed of 2500 rpm: Between 13.1 g/sec and 18.9 g/sec (shift position: N, A/C: OFF).
NG -- REPLACE MASS AIR FLOW METER
OK -- CHECK FOR INTERMITTENT PROBLEMS