P0303
3UZ-FE ENGINE CONTROL SYSTEM: SFI SYSTEM: P0300-P0308: 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
DTC P0307 - Cylinder 7 Misfire Detected
DTC P0308 - Cylinder 8 Misfire Detected
DESCRIPTION
- When a misfire occurs in the engine, hydrocarbons (HC) enter the exhaust in high concentrations. If the HC concentration is too high, exhaust emission levels may increase. High concentrations of HC can also cause the temperature of the catalyst to increase, possibly damaging the catalyst. To prevent the 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 begin flashing the MIL. For monitoring misfires, 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 records how many times the crankshaft rotation speed variations exceed threshold values.
- If the misfiring rate exceeds the threshold value and could cause emissions to deteriorate, the ECM illuminates the MIL and sets a DTC.
HINT
In some cases, several DTCs for misfired cylinders (DTCs P0301 to P0308) are recorded but the random/multiple cylinder misfire DTC (P0300) is not recorded. This is an indication that the misfires were detected and recorded at different times. Random misfire codes are recorded only when several misfires occur at the same time.
Reference: Inspection using an oscilloscope.
With the engine idling, check the waveform between terminals #1 to #8 and E1 of the ECM connectors.
The correct waveform is as shown.
MONITOR DESCRIPTION
The ECM illuminates the MIL as follows (2 trip detection logic is used and DTC is stored after 2 trip detection):
- The misfiring rate exceeds a threshold value and could cause emissions to deteriorate.
- During the first 1000 crankshaft revolutions after engine starts, an excessive misfire count (approximately 20 to 50 misfires per 1000 crankshaft revolutions) occurs once.
- An excessive misfire rate (approximately 20 to 60 times misfires per 1000 crankshaft revolutions) occurs 4 times.
The ECM begins flashing the MIL as follows (2 trip detection logic is used and DTC is stored after 2 trip detection):
- Within 200 crankshaft revolutions at a high rpm, the threshold for "percent of misfires causing catalyst damage" is reached once.
- Within 200 crankshaft revolutions at a normal rpm, the threshold for "percent of misfires causing catalyst damage" is reached 3 times.
MONITOR STRATEGY
TYPICAL ENABLING CONDITIONS
Monitor period of emission-related misfire:
Monitor period of catalyst-damage misfire:
TYPICAL MALFUNCTION THRESHOLDS
Emission-related-misfire:
Catalyst-damage-misfire (MIL blinks):
MONITOR RESULT
Refer to CHECKING MONITOR STATUS Mode 6 Data.
WIRING DIAGRAM
CONFIRMATION DRIVING PATTERN
- Connect the Techstream to the DLC3.
- Record the DTC and freeze frame data.
- Set check mode on the Techstream Reading and Clearing Diagnostic Trouble Codes.
- Read the value on the misfire counter for each cylinder when idling. If the value is displayed on the misfire counter, skip the following confirmation driving procedure.
- Drive the vehicle several times while using the Data List's Misfire RPM and Misfire Load menu items to keep track of the vehicle's engine speed, load and its surrounding range.
- If you have no Techstream, turn the ignition switch OFF after the symptom is simulated once. Then repeat the simulation process.
HINT
In order to force output of the DTC, it is necessary to drive with Misfire RPM and Misfire Load selected in the Data List for the period of time in the chart below. Do not turn the ignition switch OFF. Turning the ignition switch OFF switches the diagnosis system from check mode to normal mode and all DTCs, freeze frame data and other data are erased.
- Check if a misfire occurs by monitoring DTC output and the freeze frame data. Then, record the DTCs, freeze frame data and misfire counter data.
- Turn the ignition switch OFF and wait for at least 5 seconds.
INSEPCTION PROCEDURE
HINT
- If DTCs other than misfire DTCs are output simultaneously, troubleshoot the non-misfire DTCs first.
- Read freeze frame data using the Techstream. Freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, freeze frame data can help determine if the vehicle was running or stopped, 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 occur when the vehicle is brought to the workshop, the misfire can be confirmed by reproducing the conditions recorded in the freeze frame data. Also, after finishing repairs, confirm that no misfire occurs (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 range or the misfire occurs only in a high engine speed area, only general fault code P0300 will be stored.
- When only P0300 is stored:
* Erase the general misfire fault code from the Techstream.
* Start the engine and perform the confirmation driving pattern (see confirmation driving pattern).
* Read the value of the misfire count for each cylinder. Or, check if a DTC was output.
* Perform repairs on the cylinder that has a high misfire count. Or repair the cylinder indicated by any output DTCs.
* After finishing repairs, perform the confirmation driving pattern again and confirm that no misfire occurs.
- If either Short FT #1, Long FT #1, Short FT #2 or Long FT #2 in the freeze frame data is +-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 75°C (167°F), a misfire is only possible during engine warm-up.
- If the misfire cannot be reproduced, the cause may be: 1) low fuel in the vehicle, 2) improper fuel in the vehicle, 3) a contaminated ignition plug, or 4) another problem.
- Be sure to check the value on the misfire counter after repairs.
- An extremely imbalanced drive wheel, which causes body vibration, may cause misfire DTCs detection.
NOTICE:
Inspect the fuses for circuits related to this system before performing the following inspection procedure.
PROCEDURE
1. CHECK OTHER DTC OUTPUT (IN ADDITION TO MISFIRE DTCS)
(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 / Trouble Codes.
(e) Read the 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 Diagnostic Trouble Code Descriptions
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 to ON.
(c) Turn the Techstream on.
(d) Enter the following menus: Powertrain / Engine / Data List / 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.
3. CHECK CONNECTION OF PCV HOSE
OK:
PCV hose is connected correctly and is not damaged.
NG -- REPAIR OR REPLACE PCV HOSE
OK -- Continue to next step.
4. READ VALUE USING TECHSTREAM (CYLINDER #1 MISFIRE COUNT #2, #3, #4, #5, #6, #7 AND #8)
(a) Enter the following menus: Powertrain / Engine / Data List / Cylinder #1 Misfire Count, #2, #3, #4, #5, #6, #7 and #8.
(b) Start the engine and allow the engine to idle.
(c) Read each value for Cylinder #1 Misfire Count to #4 displayed on the tester. If no misfire counts occur in any cylinders, perform steps (d) and (e) and then check the misfire counts again.
(d) Drive the vehicle with the Misfire RPM and Misfire Load noted in the "READ VALUE USING TECHSTREAM (MISFIRE RPM AND MISFIRE LOAD)" procedures above.
(e) Read the Cylinder #1 Misfire Count to #4 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 right after the engine is started.
B -- CHECK AIR INDUCTION SYSTEM
A -- Continue to next step.
5. INSPECT SPARK PLUG
(a) Remove the engine cover.
(b) Remove the ignition coil and the spark plug of the misfire cylinder.
(c) Measure the spark plug electrode gap.
Standard gap:
The electrode gap is 1.0 to 1.3 mm (0.039 to 0.051 in.).
(d) Check the electrode for carbon deposits.
Recommended spark plug:
NOTICE:
If the electrode gap is out of the standard, replace the spark plug. Do not adjust the electrode gap.
NG -- REPLACE SPARK PLUG
OK -- Continue to next step.
6. CHECK FOR SPARKS AND IGNITION
(a) Disconnect the injector connectors to prevent the engine from starting.
CAUTION:
Always disconnect all injector connectors.
(b) Remove the ignition coil from the cylinder head.
(c) Install the spark plug to the ignition coil.
(d) Attach the spark plug to the cylinder head cover.
(e) Crank the engine for 2 seconds or less and check if a spark occurs.
NOTICE:
Do not crank the engine for more than 2 seconds.
OK:
Sparks jump across electrode gap.
NG -- CHANGE TO NORMAL SPARK PLUG AND CHECK SPARK OF MISFIRING CYLINDER
OK -- Continue to next step.
7. CHECK CYLINDER COMPRESSION PRESSURE ON MISFIRING CYLINDER
(a) Measure the cylinder compression pressure of the misfiring cylinder Engine.
NG -- CHECK ENGINE TO DETERMINE CAUSE OF LOW COMPRESSION
OK -- Continue to next step.
8. INSPECT FUEL INJECTOR (POWER SOURCE)
(a) Disconnect the fuel injector connectors.
(b) Measure the voltage according to the value(s) in the table below.
Standard Voltage:
NG -- CHECK HARNESS AND CONNECTOR (FUEL INJECTOR - IG2 RELAY)
OK -- Continue to next step.
9. CHECK HARNESS AND CONNECTOR (ECM - FUEL INJECTOR)
(a) Disconnect the ECM connectors.
(b) Disconnect the fuel injector connectors.
(c) Measure the resistance according to the value(s) in the table below.
Standard Resistance (Check for Open):
Standard Resistance (Check for Short):
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.
10. CHECK FUEL INJECTOR OF MISFIRING CYLINDER
(a) Check the injector injection (whether fuel volume is high or low, and whether injection pattern is poor) Testing and Inspection.
NG -- REPLACE FUEL INJECTOR Service and Repair
OK -- Continue to next step.
11. CHECK VALVE CLEARANCE OF MISFIRING CYLINDER
(a) Check the valve clearance Adjustments.
NG -- ADJUST VALVE CLEARANCE
OK -- Continue to next step.
12. CHECK AIR INDUCTION SYSTEM
(a) Check the air induction system for vacuum leak Intake System.
OK:
No leak from air induction system.
NG -- REPAIR OR REPLACE AIR INDUCTION SYSTEM
OK -- Continue to next step.
13. CHECK VALVE TIMING
(a) Remove the engine cover.
(b) Remove the drive belt.
(c) Remove the timing belt cover LH and RH.
(d) Turn the crankshaft to align the matchmarks of the crankshaft.
(e) Align the notch of the crankshaft pulley with the "0" position.
(f) Confirm whether the matchmarks of the camshaft pulley and cylinder head cover are facing each other.
(g) If the matchmarks are not facing each other, turn the crankshaft clockwise by 360°. Confirm again if the matchmarks are facing each other.
OK:
The matchmarks of the camshaft pulley and the cylinder head cover face each other when the notch of the crankshaft pulley is in the "0" position.
NG -- ADJUST VALVE TIMING
OK -- Continue to next step.
14. CHECK FUEL PRESSURE
(a) Check the fuel pressure Testing and Inspection.
NG -- CHECK AND REPLACE FUEL PUMP, PRESSURE REGULATOR, FUEL LINE AND FILTER
OK -- Continue to next step.
15. READ VALUE USING TECHSTREAM (COOLANT TEMP)
(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 / Data List / Coolant Temp.
(e) Read the Coolant Temp value when the engine is cold and warmed up.
Standard:
ECT when the engine is cold: Same as ambient temperature
ECT when the engine is warmed up: 75 to 95°C (167 to 203°F)
NG -- REPLACE ENGINE COOLANT TEMPERATURE SENSOR
OK -- Continue to next step.
16. INSPECT MASS AIR FLOW METER P0171
NG -- REPLACE MASS AIR FLOW METER Service and Repair
OK -- REPLACE ECM Service and Repair
17. CHECK AIR INDUCTION SYSTEM
(a) Check the air induction system for vacuum leak Intake System.
NG -- REPAIR OR REPLACE AIR INDUCTION SYSTEM
OK -- Continue to next step.
18. CHECK VALVE TIMING
(a) Remove the engine cover.
(b) Remove the drive belt.
(c) Remove the timing belt cover LH and RH.
(d) Turn the crankshaft to align the matchmarks of the crankshaft.
(e) Align the notch of the crankshaft pulley with the "0" position.
(f) Confirm whether the matchmarks of the camshaft pulley and cylinder head cover are facing each other.
(g) If the matchmarks are not facing each other, turn the crankshaft clockwise by 360°. Confirm again if the matchmarks are facing each other.
OK:
The matchmarks of the camshaft pulley and the cylinder head cover face each other when the notch of the crankshaft pulley is in the "0" position.
NG -- ADJUST VALVE TIMING
OK -- Continue to next step.
19. CHECK FUEL PRESSURE
(a) Check the fuel pressure Testing and Inspection.
NG -- REPAIR OR REPLACE FUEL PUMP, PRESSURE REGULATOR, FUEL PIPE LINE OR FILTER
OK -- Continue to next step.
20. READ VALUE USING TECHSTREAM (COOLANT TEMP)
(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 / Data List / Coolant Temp.
(e) Read the Coolant Temp value when the engine is cold and warmed up.
Standard:
ECT when the engine is cold: Same as ambient temperature
ECT when the engine is warmed up: 75 to 95°C (167 to 203°F)
NG -- REPLACE ENGINE COOLANT TEMPERATURE SENSOR
OK -- Continue to next step.
21. INSPECT MASS AIR FLOW METER P0171
NG -- REPLACE MASS AIR FLOW METER Service and Repair
OK -- Continue to next step.
22. INSPECT SPARK PLUG
(a) Remove the engine cover.
(b) Remove the ignition coil and the spark plug of the misfire cylinder.
(c) Measure the spark plug electrode gap.
Standard gap:
The electrode gap is 1.0 to 1.3 mm (0.039 to 0.051 in.).
(d) Check the electrode for carbon deposits.
Recommended spark plug:
NOTICE:
If the electrode gap is out of the standard, replace the spark plug. Do not adjust the electrode gap.
NG -- REPLACE SPARK PLUG
OK -- Continue to next step.
23. CHECK FOR SPARKS AND IGNITION
(a) Disconnect the injector connectors to prevent the engine from starting.
CAUTION:
Always disconnect all injector connectors.
(b) Remove the ignition coil from the cylinder head.
(c) Install the spark plug to the ignition coil.
(d) Attach the spark plug to the cylinder head cover.
(e) Crank the engine for 2 seconds or less and check if a spark occurs.
NOTICE:
Do not crank the engine for more than 2 seconds.
OK:
Sparks jump across electrode gap.
NG -- CHANGE TO NORMAL SPARK PLUG AND CHECK SPARK OF MISFIRING CYLINDER
OK -- Continue to next step.
24. CHECK CYLINDER COMPRESSION PRESSURE ON MISFIRE CYLINDER
(a) Measure the cylinder compression pressure of the misfiring cylinder Engine.
NG -- CHECK ENGINE TO DETERMINE CAUSE OF LOW COMPRESSION
OK -- Continue to next step.
25. INSPECT FUEL INJECTOR (POWER SOURCE)
(a) Disconnect the fuel injector connectors.
(b) Measure the voltage according to the value(s) in the table below.
Standard Voltage:
NG -- CHECK HARNESS AND CONNECTOR (FUEL INJECTOR - IG2 RELAY)
OK -- Continue to next step.
26. CHECK HARNESS AND CONNECTOR (ECM - FUEL INJECTOR)
(a) Disconnect the ECM connectors.
(b) Disconnect the fuel injector connectors.
(c) Measure the resistance according to the value(s) in the table below.
Standard Resistance (Check for Open):
Standard Resistance (Check for Short):
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.
27. CHECK FUEL INJECTOR OF MISFIRE CYLINDER
(a) Check the injector injection (whether fuel volume is high or low, and whether injection pattern is poor) Testing and Inspection.
NG -- REPLACE FUEL INJECTOR Service and Repair
OK -- Continue to next step.
28. CHECK VALVE CLEARANCE OF MISFIRE CYLINDER
(a) Check the valve clearance Adjustments.
NG -- ADJUST VALVE CLEARANCE
OK -- REPLACE ECM Service and Repair
29. CHECK HARNESS AND CONNECTOR (FUEL INJECTOR - IG2 RELAY)
(a) Disconnect the fuel injector connectors.
(b) Remove the IG2 relay from the engine room No. 1 relay block.
(c) Measure the resistance according to the value(s) in the table below.
Standard Resistance (Check for Open):
Standard Resistance (Check for Short):
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- CHECK ECM POWER SOURCE CIRCUIT ECM Power Source Circuit
30. CHANGE TO 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.
NOTICE:
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 a spark occurs while the engine is being cranked.
OK:
Spark jumps across electrode gap.
NG -- CHANGE TO NORMAL IGNITION COIL AND CHECK SPARK OF MISFIRING CYLINDER
OK -- REPLACE SPARK PLUG
31. CHANGE TO NORMAL IGNITION COIL AND CHECK SPARK OF MISFIRING CYLINDER
(a) Change the ignition coil to a ignition coil that functions normally.
(b) Perform a spark test.
CAUTION:
Always disconnect all injector connectors.
NOTICE:
Do not crank the engine for more than 2 seconds.
(1) Install the spark plug into 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 ECM Service and Repair
OK -- REPLACE IGNITION COIL