P0304
DTC P0300 RANDOM/MULTIPLE CYLINDER MISFIRE DETECTEDDTC P0301 CYLINDER I-MISFIRE DETECTED
DTC P0302 CYLINDER 2-MISFIRE DETECTED
DTC P0303 CYLINDER 3-MISFIRE DETECTED
DTC P0304 CYLINDER 4-MISFIRE DETECTED
GENERAL DESCRIPTION
The Misfire monitor diagnostic is based on crankshaft rotation velocity variation. The ECM determines crankshaft rotational velocity using the crankshaft position sensor and camshaft position sensor. When a cylinder misfires the crankshaft slows down momentarily. By monitoring the crankshaft and camshaft position sensor signals, the ECM can calculate when a misfire occurs. For a non-catalyst damaging misfire, the diagnostic will be required to report a misfire present within 1000 - 3200 engine revolutions. For catalyst damaging misfire, the diagnostic will respond to monitor 200 engine revolutions. Rough roads may cause false misfire detection. The rough road (acceleration) sensor consists of a piezoelectric vibration pick up which detects vertical acceleration of the vehicle. The sensor signal is used by the ECM to determine the degree of vertical movement of the car, for example, on a bumpy road. Since this may also cause uneven engine running, the ECM uses the signal to distinguish the phenomenon from actual misfiring.
DTC DESCRIPTION
If the ECM detects that engine speed variation indicates a misfire sufficient to cause three-way catalyst converter damage or emissions level to exceed standard value, the ECM sets misfire DTC P0301 ,P0302, P0303 or P0304. If the misfire rate is high enough to damage the catalyst, the MIL will flash to alert the vehicle operator. With a more than two cylinder misfire detection, the ECM sets P0300.
DTC Detecting Condition:
Specification:
MONITOR DTC STATUS
NOTE: If any DTCs related to injectors, HO2S, ECT (Engine Coolant Temperature) Sensor, Throttle Position sensor or Mass Air Flow Sensor are stored, do ALL REPAIRS associated with those codes before proceeding with this troubleshooting procedure.
If the misfire rate is high enough to cause possible catalyst damage (if the MIL was blinking), ensure that the monitoring for DTC P0420 is completed and passed after verifying the misfire repair.
1. Connect scan tool and select "Diagnostic Trouble Codes (DTCs)" mode.
2. Press F4 (DTAL) to select DTC information from the DTCs menu.
3. Confirm that "DTC Readiness Flag" indicates "Complete". If not, drive the vehicle within conditions noted in the freeze frame data or enable conditions.
4. Read "DTC Status" parameter.
5. Is parameter displayed "History (Not Present) fault"?
NOTE:
- History (Not Present) fault : DTC occurred but has been cleared.
- Present fault : DTC is occurring at present time.
YES - Fault is intermittent caused by poor contact in the sensor's and/or ECM's connector or was repaired and ECM memory was not cleared. Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and then go to "Verification of Vehicle Repair" procedure.
NO - If any misfire DTCs related to companion cylinders {P0301 (Cylinder 1) & P0304 (Cylinder 4 ), P0302 (Cylinder 2)) & P0303 (Cylinder 3)) are also stored, go to "Ignition System Inspection" procedure. If not, go to next step as below
VISUAL INSPECTION
l. Visually/physically inspect for the following conditions
- Vacuum hoses in engine room for splits, kinks and improper installation
- Positive crankcase ventilation valve for improper installation, damaged O-rings and malfunctioning
- Verify that the ECM ground connections are clean and properly tightened.
2. Check MAFS and ECTS for the following conditions:
- Contamination, deterioration, poor connection or damaged harness
- The MAF signal displayed on the scantool should increase as engine speed increases
- The engine coolant temperature displayed on the scantool should close to the actual coolant temperature.
3. Was a problem found in any of the above areas?
YES - Replace or repair as necessary and go to "Verification of Vehicle Repair" procedure
NO - Go to next step as below
TIMING INSPECTION
1. With ignition "OFF", set up an oscilloscope as follows
Channel A (+): Terminal 3 of the Crankshaft Position Sensor (CKPS), (-): Ground
Channel B (+): Terminal 3 of the Camshaft Position Sensor (CMPS), (-): Ground
2. Start the engine and check for signal waveform whether synchronize with camshaft sensor or not.
3. Is the signal waveform normal?
YES - Go to next step as below
NO - Repair or readjust as necessary, if air gap of the CKPS is exceeds specification [0.3 - 1.7 mm. (0.012 - 0.067 in.)]. If OK, check that the crankshaft and camshaft are correctly aligned the matching marks of the pulleys. Repair or readjust as necessary and go to "Verification of Vehicle Repair" procedure
IGNITION SYSTEM INSPECTION
1. Spark Plug Cable & Ignition Coil Inspection
1. Visually/physically inspect the spark plug cable and ignition coil related to the misfiring cylinder(s) for the following conditions
- Damage, cracks, carbon and flashover
- Poor connection or damaged harness
- Connected to the incorrect cylinders at the ignition coil and spark plug
2. Measure the resistance of the spark plug cable related to the misfiring cylinder(s)
Specification : 5.6 Kohms/m ± 20%
3. Measure the resistance of the primary and secondary ignition coil related to the misfiring cylinder(s)
Specification :
Primary Ignition Coil Resistance : 0.56 - 0.68 Ohms at 20 °C(68 °F)
Secondary ignition Coil Resistance : 6 - 8 Kohms at 20 °C(68 °F)
4. Was a problem found in any of the above areas?
YES - Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure
NO - Go to next step as below
2. Spark Plug Inspection
1. Visually/physically inspect the spark plug related to the misfiring cylinder(s) for the following conditions
- Damaged insulation, Worn electrodes, Oil or fuel fouled, Loose terminals and cracks
- Check for electrode gap : 1.0 - 1.1 mm. (0.039 - 0.043 in.)
- Check if the spark plug for the relevant cylinder is lighter in color than the other plugs.
2. Was a problem found in any of the above areas?
YES - Replace or adjust as necessary and go to "Verification of Vehicle Repair" procedure
NO - Go to next step as below
FUEL SYSTEM INSPECTION
1. Fuel Line Pressure Inspection
1. Check the fuel for excessive water, alcohol, or other contaminants. Replace contaminated fuel as necessary.
2. Install a fuel pressure gage.
3. Inspect fuel pressure with normal idle status.
Specification : 338 - 348 kPa(3.45 - 3.55 kg/sq.cm)
4. Is fuel pressure within the specified value?
YES - Go to next step as below
NO - Inspect the suspected area. Refer to table as below. Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure.
2. Fuel Pressure Hold Inspection
1. Stop the engine and check for a change in the fuel pressure gauge reading.
Specification : After engine stops, the gauge reading should hold for minimum 5 minutes
2. Is fuel pressure within the specified value?
YES - Go to next step as below
NO - Inspect the suspected area. Refer to table as below. Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure.
ENGINE COMPRESSION TEST
1. Warm up the engine to normal operating temperature. Verify the battery must be at or near full charge.
2. With ignition "OFF", disconnect the ignition coil connectors and the spark plug cables.
3. Install compression pressure gauge to the spark plug hole.
4. With wide open throttle by hand, cranking the engine and record the compression readings from all of the cylinders.
Specification :
Compression pressure : 1,283 kPa(1 3.0 kgf/sq.cm, 185 psi)
Minimum pressure : 1,135 kPa(11.5 kgf/sq.cm, 164 psi)
Difference between each cylinder : 100 kPa(1.0 kgf/sq.cm, 15 psi) or less
5. Is compression pressure within the specified value?
YES - Verify if the engine has excessive coolant consumption. If yes, check for damaged inlet water passage, engine block, cylinder head or head gasket. Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure
NO - If the cylinder compression in 1 or more cylinders is low, pour a small amount of engine oil into the cylinder through the spark plug hole and repeat compression test for cylinders with low compression pressure.
- If adding oil helps the compression, it is likely that the piston rings and/or cylinder bore are worn or damaged.
- If pressure stays low, a valve may be sticking or seating is improper, or there may be leakage past the gasket. Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure
VERIFICATION OF VEHICLE REPAIR
After a repair, it is essential to verify that the fault has been corrected.
1. Connect scan tool and select "Diagnostic Trouble Codes (DTCs)" mode.
2. Press F4 (DTAL) and confirm that "DTC Readiness Flag" indicates "Complete". If not, drive the vehicle within conditions noted in the freeze frame data or enable conditions.
3. Read "DTC Status" parameter.
4. Is parameter displayed "History (Not Present) fault"?
YES - System performing to specification at this time. Clear the DTC
NO - Go to the applicable troubleshooting procedure.