P0300
DTC P0300 MULTIPLE CYLINDER MISFIRE DETECTEDComponent Location:
GENERAL DESCRIPTION
The Misfire monitor diagnostic is based on crankshaft rotation velocity variation. The PCM 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 PCM 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 PCM 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 PCM uses the signal to distinguish the phenomenon from actual misfiring.
DTC DESCRIPTION
The PCM must monitor the engine for misfiring possibly caused by ignition coil defects or injector fails. If misfiring is detected, the PCM identify the cylinder(s) that has (have) misfired and calculate misfiring rate for a given duration. The DTC for Misfire (P0301 to 0304) is set as soon as misfiring rate exceed the limit which result in damage to the catalyst or increase emissions. The PCM stores individual DTC for the cylinder has more than 10% of total misfire rate. With more than two cylinders misfire detection, the PCM sets P0300.
If the misfire rate is not extremely high, the MIL will be illuminated in the next driving cycle that diagnostic runs and fails. with extremely high misfire rate which has a danger of burning up the catalyst, the MIL blinks immediately.
DTC Detecting Condition:
NOTE: If any injectors, HO2S, ECTS, and MAP codes are present, do all repairs associated with those codes before proceeding this troubleshooting guide.
Specification:
Schematic Diagram:
SIGNAL WAVEFORM & DATA
This figures show the wave form of primary coil measured at terminal 2 of ignition coil at idle.is ON named DWELL and its normal voltage is below 0.5 V.
1. The voltage at point 0 is power supply of IG coil and it should be battery voltage
2. The signal at 02 is the duration when power TR in PCM is ON named DWELL arid its normal voltage is below 0.5 V. In case over 0.5 V
Possible cause: Faulty power TR in PCM or poor PCM ground connection.
3. The wave form at 03 is surge voltage which occurs at primary coil when power TR off and its normal voltage is over 320 V.
In case when surge voltage is low Possible cause: Open circuit in power line or poor ground connection.
MONITOR DTC STATUS
This is the inspection procedure to determine whether it is present DTC or memoried one by monitoring the current signal or by using the function of oscilloscope with Hi-scan pro.
1. Connect scantool to Data Link Connector(DLC).
2. Warm up the engine to normal operating temperature.
3. Monitor the "Ignition timing" parameter on the scantool.
NOTE: The data shown above is only for reference and there maybe a little difference actually
Specification
Idle: 0 - 20° BTDC
3000 rpm: 29 - 49° BTDC
4. Is parameter displayed within specifications?
YES: Fault is intermittent caused by poor contact in the sensor's and/or PCM's connector or was repaired and PCM 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: Go to "W/Harness Inspection" procedure.
TERMINAL & CONNECTOR INSPECTION
1. Many malfunctions in the electrical system are caused by poor harness and terminals. Faults can also be caused by interference from other electrical systems, and mechanical or chemical damage.
2. Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination,deterioration, or damage.
3. Has a problem been found?
YES: Repair as necessary and go to Verification of vehicle Repair" procedure.
NO: Go to "Power circuit inspection" procedure.
POWER CIRCUIT INSPECTION
1. Ignition "OFF"
2. Disconnect ignition coil connector.
3. Ignition "ON" & Engine "OFF"
4. Measure voltage between terminal 1 of sensor harness connector and chassis ground.
Specification: approximately B+
5. Is measure voltage within Specification?
YES: Go to "Signal circuit inspection" procedure.
NO:
- Open or Short circuit to chassis ground between ignition coil harness connector and ignition switch harness connector.
- Repair as necessary and go to "Verification Vehicle Repair" procedure.
NOTE: In case, when ignition connector is disconnected, the voltage at terminal 1 is 0 V
- Possible cause: Open or short circuit of battery line between FUSE 10(10 A) of P/C-J/BOX and terminal 1 of ignition coil.
SIGNAL CIRCUIT INSPECTION
1. Check for CKPS signal
1. Engine "ON"
2. Monitor waveform at the terminal 1 of CKPS.
3. Is the waveform displayed normally?
YES: Go to "Component Inspection" procedure.
NO:
- Go to "PO335 Crankshaft position sensor - no signal" procedure.
- Repair as necessary and go to "Verification Vehicle Repair" procedure.
COMPONENT INSPECTION
1. Check for ignition coil and plug wires
1. Turn ignition switch to OFF and disconnect ignition coil connector.
2. Check ignition coil and plug wires for cracks or carbon tracing.
3. Check resistance of primary coil.
Specification: Primary coil resistance: 0.87 Ohms ± 10%
4. Check resistance of secondary coit.
Specification: Secondary coils resistance: 13.0 kOhms ± 15%
5. Check for resistance of plug wires.
Specification :Plug wire: 5.6 kOhms/m ± 20%
6. Is the resistance of ignition coils and plug wires within specification?
YES: Go to "Check for spark plug "as below.
NO:
- Faulty ignition coils or plug wires.
- Repair as necessary and go to "Verification Vehicle Repair" procedure.
2. Check for spark plug
Check the following items below for spark plug.
1. Remove spark plugs and check gap and plug condition.
2. Check the electrode condition (wear or carbon deposit)
3. Check the insulators condition (crack,etc.)
4. Check the carbon deposit
Specification : gap: 1.0 - 1.1 mm
5. Are spark plugs gapped properly and in good condition?
YES: Go to "Check for vacuum and PCV" as below.
NO:
- Faulty spark plugs.
- Repair as necessary and go to "Verification Vehicle Repair" procedure.
3. Check for vacuum and PCV
Check for any split, disconnected or perforated vacuum hoses. Also, check PCV valve for proper operation.
1. Remove the positive crankcase ventilation valve.
2. Insert a thin stick into the positive crankcase ventilation valve from the threaded side to check that the plunger moves.
3. If the plunger does not move,the positive crankcase ventilation valve is clogged.Clean or replace it.
4. Are vacuum hoses and PCV okay?
YES: Go to "System inspection" procedure.
NO:
- Replace faulty vacuum hoses or PCV.
- Repair as necessary and go to "Verification Vehicle Repair" procedure.
SYSTEM INSPECTION
1. Check for fuel pressure
1. Reduce the internal pressure of the fuel pipe and hoses and cover the hose connection with a shop towel to prevent splashing of fuel.
2. Remove the bolt connecting the fuel line to the fuel delivery pipe.
3. Using the fuel pressure gauge adaptor,install the fuel pressure gauge to the fuel pressure gauge adaptor.
4. Apply battery voltage to the terminal for he pump drive and activate the fuel pump: then, with fuel pressure applied, check fuel leakage from the pressure gauge or connection part.
5. Start an engine and warm up to operating temperature.
6. Check for fuel pressure at idle.
Specification : Fuel pressure at idle: 51 psi(350 kPa, 3.5 kg/sq.cm)
7. Is fuel pressure within specification?
YES: Go to "Compression test" as below.
NO:
- Check fuel delivery system.
- Repair as necessary and go to Verification Vehicle Repair procedure.
2. Compression test
1. Perform compression test at 300 rpm.
Specification:
Approximately: 193 psi (1360 kPa, 13.5 kg/sq.cm)
No more than 10% between highest and lowest cylinder.
2. Is fuel pressure within specification?
YES: Substitute with a known-good PCM and check for proper operation. If the problem is corrected, replace PCM and then go to "Verification of Vehicle Repair" procedure.
NO:
- Perform leak down test to determine source of low compression.
- Repair as necessary and go to "Verification Vehicle Repair" procedure.
VERIFICATION OF VEHICLE REPAIR
After a repair, it is essential to verify that the fault has been corrected.
1. Monitor and record the Freeze Frame Data for the Diagnostic Trouble Code (DTC) which has been diagnosed.
2. Using a Scantool, Clear the DTCs.
3. Operate the vehicle within conditions noted in the freeze frame data or enable conditions.
4. Monitor that all rediness test have been verified as "Complete"
5. Are any DTCs present?
YES: Go to the applicable troubleshooting procedure.
NO: System is performing to specification at this time.