DTC P0300, P0301, P0302, P0303, P0304, P0305 Or P0306: Cylinder Misfire/Multiple Cylinder Misfire

If misfire occurs, engine speed will fluxuate and appropriate DTC will set in ECM as follows:

• DTC P0300; multiple cylinder misfire.
• DTC P0301; cylinder No. 1.
• DTC P0302; cylinder No. 2.
• DTC P0303; cylinder No. 3.
• DTC P0304; cylinder No. 4.
• DTC P0305; cylinder No. 5.
• DTC P0306; cylinder No. 6.

1. Basic Inspection  - Check for vacuum leaks. Check for correct fuel pressure and ignition timing. Check exhaust system for restrictions. Check EGR system for correct operation. Repair if necessary. If no faults are found, go to next step.
2. Check Fuel System  - Start engine and allow to idle. Listen to each injector to verify operational sound (clicking noise). Individually, disconnect fuel injector wiring harness connectors. If engine speed momentarily drops, go to next step. If engine speed does not momentarily drop, go to step 5).
3. Check Ignition System  - Check ignition system for defective or mis-routed wiring. Check spark plugs for correct application, gap, wear or fouling. Check ignition coil, power resistor and related circuitry. See SYSTEM/COMPONENT TESTS article.
4. Check ECM  - Turn ignition off. Disconnect ECM wiring harness connector. Inspect pins for damage or corrosion and repair as necessary. Connect ECM and retest vehicle. If fault is still present, install a known good ECM and retest vehicle. If fault is still present, verify DTC is still present. If DTC is still present, repeat step 1).