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OBD-II codes are universal, meaning all models would use the same code for the same diagnostic description, though causes and repair procedure might differ.
Here are the definition of the group of codes and what Autozone recommends might not solve the problem. Misfires can be due to various causes.
DTC P0301, DTC P0302, DTC P0303 & DTC P0304
" DTC P0301: Cylinder No. 1 Misfire Detected
" DTC P0302: Cylinder No. 2 Misfire Detected
" DTC P0303: Cylinder No. 3 Misfire Detected
" DTC P0304: Cylinder No. 4Misfire Detected
NOTE: Engine Control Module (ECM), can also be referred to as Powertrain Control Module (PCM).
NOTE: Testing individual components does not isolate shorts or opens. Perform all voltage tests using a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless stated otherwise in test procedure. Use ohmmeter to isolate wiring harness shorts or opens.
With ignition switch at ON or START position, voltage is applied to ignition coil. Ignition coil consists of two coils and they are located on cylinder head spark plugs No. 1 and 2. High tension leads goes from cylinder ignition coil No. 1 to cylinder No. 4 and from cylinder ignition coil No. 2 to cylinder No 3. Ignition coil fires two spark plugs on every power stroke (cylinder under compression and cylinder on exhaust stroke). Coil number one fires cylinders 1 and 4. Coil number two fires cylinders 2 and 3. Powertrain Control Module (PCM) or Engine Control Module (ECM) provides a switching circuit to ground for energizing primary ignition coils. PCM/ECM uses crankshaft position sensor signal to time energizing of coil. When a primary ignition coil is energized and de-energized, secondary coil produces a high voltage spike across attached spark plugs. At same time, tach interface (part of ignition power transistor) provides PCM/ECM and Transaxle Control Module (TCM) with an RPM signal.
PCM/ECM detects misfire as change in angular acceleration of crankshaft. PCM/ECM will monitor for misfire when the following conditions are met:
" Engine has been running for at least 5 seconds.
" Engine speed is 500-6000 RPM.
" Engine coolant temperature is more than 14 F (-10 C).
" Intake air temperature is more than 14 F (-10 C).
" Vehicle is running free from sudden accelerations/decelerations such as gear change.
PCM/ECM sets DTCs P0301, P0302, P0303 or P0304 and turns MIL on when misfire has occurred more than 200 out of 1000 crankshaft revolutions.
If catalytic converter temperature is more than 1742 F (950 C), and misfire occurs more often than allowed in last 200 crankshaft revolutions, PCM/ECM determines severe misfire exists and will set DTCs P0301, P0302, P0303 or P0304 and cause MIL to blink.
" Faulty Ignition system related part.
" Poor Crankshaft Position (CKP) sensor signal.
" Incorrect air/fuel ratio.
" Low compression pressure.
" Faulty Engine Coolant Temperature (ECT) sensor.
" Timing belt missing teeth.
" Faulty Fuel injector.
" Faulty EGR valve.
" Faulty PCM/ECM.
1. Turn ignition off. Connect Hi-Scan Pro tool or equivalent to OBD-II Data Link Connector (DLC). Turn ignition on. Monitor and verify DTCs P0301, P0302, P0303 or P0304 are set. Go to next step. If DTCs P0201, P0202, P0203 or P0204 are set, do all repairs associated with those DTCs before continuing with this procedure.
2. Ensure vehicle is fueled with at least 87 octane fuel. If vehicle is fueled as specified, go to next step. If vehicle is not fueled as specified, refuel vehicle with 87 or higher octane. Go to step 5.
3. Turn ignition off. Disconnect ignition coils 3-pin harness connector. Measure primary coil resistance between ignition coil connector terminal No. 1 and 2 (component side). Resistance should be approximately 1.3 ohms. Disconnect spark plug wires from ignition coils. Measure secondary coils resistance between ignition coils spark plug wires connectors No. 1 and 4, also between No. 2 and 3. Resistance should be between 10.3-13.9 k/ohms. If both resistances are as specified, go to next step. If any resistance is not as specified, replace ignition coil with known-good component. After repair, go to step 5.
4. Perform an inspection of following systems and components:
" Spark plug and spark plug wires for cracks or damage.
" Fuel injectors clogging or wiring damage.
" Obstruction of Mass Air Flow (MAF) sensor.
" Vacuum hoses for damage or leaks.
If all components are in good operation condition, Verify than PCM/ECM connectors are secure. If connectors are okay, replace PCM/ECM with known-good component. Go to next step. If any component is faulty, repair or replace as necessary. Go to next step.
5. Return vehicle to original condition. Clear codes using Hi-Scan Pro tool or equivalent. Verify repairs by driving vehicle and monitoring for pending codes. If DTC is set during test drive, follow appropriate DTC test procedure.
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Wednesday, November 10th, 2010 AT 8:04 AM