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Home >> Mazda >> 2002 >> MX-5 Miata Base, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0301: CYLINDER No. 1 MISFIRE DETECTION, DTC P0302: CYLINDER No. 2 MISFIRE DETECTION, DTC P0303: CYLINDER No. 3 MISFIRE DETECTION OR DTC P0304: CYLINDER No. 4 MISFIRE DETECTION >> Diagnostic Procedure

Diagnostic Procedure

  1. Turn ignition off. Connect New Generation Star (NGS) tester or equivalent to OBD-II Data Link Connector-2 (DLC-2). See Figure. Turn ignition on. Monitor for FREEZE FRAME DATA and ensure data has been recorded. Check for service bulletins and/or other line of repair information related to this DTC. If repair information is available, perform diagnosis and repair as necessary. After repair, go to step  12. If repair information is not available, go to next step.
  2. Monitor for DTC or pending coderelated to this DTC. If other DTC is present, follow appropriate DTC diagnostic procedure. If no other DTC is present, go to next step.
  3. Start engine and let it idle until it reaches normal operation temperature. Using NGS tester or equivalent, access ECT, MAF, TP, RPM and VSS PIDs. For system PID specifications. See SYSTEMS INPUT SIGNAL SPECIFICATIONS  table. If all systems input voltages are as specified, go to next step. If any system input voltage is not as specified, inspect system sensor and system wiring harness, repair or replace as necessary. For circuit identification, see MIATA in WIRING DIAGRAMS article. After repair, go to step  12
  4. Inspect same PIDs while simulating recorded FREEZE FRAME DATA conditions, If no input signal drastically change, go to next step. If any input signal drastically change, inspect system sensor and system wiring harness, repair or replace as necessary and go to step  12.
  5. Turn ignition off. Remove spark plug from suspected cylinder. Check spark plug for cracks, excess wear, gap and wet. If spark plug is okay, go to next step. If spark is faulty, repair or replace as necessary. After repair, go to step  12.
  6. Inspect high-tension leads for installation, condition, corrosion on terminal, open lead or damaged cover. If high-tension leads are okay, go to next step. If any high-tension leads is faulty, replace high-tension lead and go to step  12.
  7. Start engine and let it run at idle speed. While spraying rust penetrating agent in short spurts, inspect for air suction (vacuum leak) due to cracks, damages, or loose parts between following components:
    CAUTION: DO NOT spray rust penetrating agent on or near coils or plug wires, an arcing wire or coil could start a fire. Allow enough time for rust penetrating agent to dissipate.
    • From throttle body to dynamic chamber.
    • From dynamic chamber to intake manifold.
    • From intake manifold to cylinder heads.

    If air suction (vacuum leak) is not found, go to next step. If air suction (vacuum leak) is found, repair or replace necessary component and go to step  12.

  8. Turn ignition off. Disconnect fuel injector 2-pin harness connector from suspected cylinder. Connect test light (led) to fuel injector harness connector terminals. While cranking engine, check dim of test light. If test light illuminate, go to next step. If test light does not illuminate, check fuel injector harness, repair or replace as necessary. After repair, go to step  12.
  9. Return vehicle to original condition. Ensure to let engine cool down before performing this test. Remove radiator cap by using thick cloth around it and turning slowly. Implement procedure to bleed air from engine coolant system. Start engine and let it idle. If any small air bubbles which makes engine coolant white at filler opening is found, determine source of air leak into cooling system (possible poor sealing of cylinder head gasket), repair and replace faulty components. After repair, go to step  12. If sealing of engine coolant passage is okay, go to next step.
  10. Return vehicle to original condition. Perform engine compression test. For proper engine compression test. See COMPRESSION under PRELIMINARY INSPECTION & ADJUSTMENTS in BASIC DIAGNOSTIC PROCEDURES article. Compression should be about 198 psi (13.9 kg/cm2 ) at 300 RPM. If engine compression is as specified, go to next step. If engine compression is not as specified, determine source of low compression. Repair as necessary and go to step  12.
  11. Turn ignition off. Inspect fuel injectors operation. See Fuel Injector test in FUEL CONTROL under FUEL SYSTEM in SYSTEM & COMPONENT TESTING - MIATA, MILLENIA, MPV, PROTEGE, PROTEGE5 & 626 article. If fuel injectors are operating properly, go to next step. If any fuel injector is faulty, replace fuel injector and go to next step.
  12. Return vehicle to original condition. Using NGS tester or equivalent, clear DTCs from PCM memory. Start engine and run DRIVE MODE 1. See DRIVE MODES  under SELF-DIAGNOSTIC SYSTEM.Monitor for pending DTCs. If same DTC P0301, P0302, P0303 or P0340 is present, replace PCM. For PCM removal and installation, see POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION article. If any other DTC is present, follow appropriate DTC diagnostic procedure.
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