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DTC P0301-P0304: Misfire In One Cylinder Detected

WARNING: This page is about a different car, the 2000 Honda Prelude. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: If DTCs P0171, P0172, P0401, P1359, P1361, P1362, P1381, P1382, P1491, or P1498 are displayed, repair those DTCs first. Listed DTCs do not apply to all models.

If misfiring is frequent enough to trigger detection of increased emission during 2 consecutive driving cycles, Malfunction Indicator Light (MIL) will illuminate, and DTC P0300 and some combination of P0301-P0304 will be stored in memory. If misfiring is frequent enough to damage catalyst, MIL will blink whenever misfiring occurs, and DTC P0300 and some combination of P0301-P0304 will be stored in memory. When misfiring stops, MIL will still remain on.

  1. If DTCs P0301, P0302, P0303, and/or P0304 is set, check for:
    • Fuel injector that is clogged, leaking fuel or air.
    • Open or shorted fuel injector circuit.
    • Injector resistor malfunction.
    • Spark plug carbon deposits, fouling or other malfunction.
    • Ignition wires open or shorting.
    • Distributor malfunction.
    • Low engine compression.
    • Valve adjustment out of specification. See ON-VEHICLE ADJUSTMENTS article.

    Repair as necessary. If no problems are found, go to next step.

  2. Start engine and listen for clicking sound at fuel injector in suspect cylinder. If injector clicks, go to next step. If injector does not click, check for open or short in harness between PCM and fuel injector. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair open or short in wiring as necessary. If wiring is okay, replace fuel injector and recheck. If fuel injector does not click, substitute a known-good PCM and recheck. See SUBSTITUTING PCM under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - INTRODUCTION article. If symptom or indication goes away, replace original PCM.
  3. Using scan tool, check and record freeze data. Perform PCM reset procedure. See PCM RESET PROCEDURE/CLEARING DTCS in SELF-DIAGNOSTICS - INTRODUCTION article. If there is no freeze data of misfiring, clear DTCs. Exchange spark plug from misfiring cylinder with one from another cylinder. Connect SCS Service Connector to 2-pin service check connector. See Figure . Test drive vehicle several times in range of freeze data if available. If there is no freeze data of misfiring, test drive vehicle under various conditions to try to duplicate malfunction. If DTC P0301, P0302, P0303 or P0304 is indicated, go to next step. If DTC is not indicated, misfire condition is intermittent due to spark plug fouling. Plugs are firing properly at this time.
  4. If misfiring occurs in other cylinder whose spark plug was exchanged, replace spark plugs. If misfiring does not occur in other cylinder whose spark plug was exchanged, exchange fuel injector with one from another cylinder. Start engine and allow it to idle for 2 minutes. Test drive vehicle several times in range of freeze data. If there is no freeze data of misfiring, test drive vehicle under various conditions to try to duplicate malfunction.
  5. If DTC P0301, P0302, P0303 or P0304 is not indicated, misfire condition is intermittent due to bad contact in fuel injector connector. Injectors are operating properly at this time. If DTC is not indicated and misfiring occurs in other cylinder whose injector was exchanged, replace faulty fuel injector. If misfiring does not occur in other cylinder whose fuel injector was exchanged, check cylinder leak down and engine compression.
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