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Home >> Toyota >> 1997 >> Tercel 4D Sedan, Standard >> Repair and Diagnosis >> Engine Performance >> Testing & Diagnosis >> Engine Control System Tests W/Codes >> Circuit Tests >> DTC P0300: Random/Multiple Misfire Detected >> Diagnosis & Repair
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Diagnosis & Repair

  1. Inspect spark plug and check for spark at misfiring cylinder. See BASIC TESTING article. Repair as necessary. If spark plug is okay and spark is present, go to next step.
  2. Access ECM behind glove box. Turn ignition on. Using DVOM, backprobe ECM connector. Measure voltage between ground and injector terminals at ECM E7 connector. See IDENTIFYING INJECTOR TERMINALS  table. See Figure. If voltage is 9-14 volts for each circuit, go to step 4). If voltage is not 9-14 volts, go to next step.
    IDENTIFYING INJECTOR TERMINALS

    Injector No. (1) Terminal No. Wire Color
    1 12 Green
    2 25 Yellow
    3 11 Red
    4 24 Blue
    (1) Terminals are located in ECM E7 connector.
  3. Disconnect injector of misfiring cylinder. Using ohmmeter, measure resistance between injector terminals. If resistance is 13.4-14.2 ohms, check for open or short circuit in wiring harness between ECM and injector. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair wiring as necessary. If resistance is not 13.4-14.2 ohms, replace injector.
  4. Check fuel pressure. See BASIC TESTING article. Repair fuel pressure as necessary. If fuel pressure is okay, check fuel injector performance. See SYSTEM/COMPONENT TESTS article. Replace fuel injectors as necessary.
  5. If all injectors are okay, check MAP sensor and ECT sensor. See SYSTEM/COMPONENT TESTS article. Replace MAP and/or ECT sensor as necessary. If both components are okay, also check engine compression, valve clearance and valve timing. See BASIC TESTING article.
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