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Home >> Toyota >> 1995 >> Tercel Base, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Diagnostic Testing >> Code P0300 - Random/Multiple Misfire Detected >> Diagnosis & Repair
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Diagnosis & Repair

  1. Inspect spark plugs and ignition system. See procedures in the BASIC TESTING article. Repair as needed. If ignition system is okay, ensure ignition is off.
  2. Access ECM harness connectors behind glove box. Turn ignition on. Using DVOM, backprobe ECM connector. Measure voltage between individual terminals #10, #20, and ground. 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.
  3. Disconnect injector of misfiring cylinder. Using ohmmeter, measure resistance between injector terminals. If resistance is 13.4-14.2 ohms, inspect circuits between ECM and injector for open or short. See wiring diagram in the WIRING DIAGRAMS article. Repair as needed. If resistance is NOT 13.4-14.2 ohms, replace injector.
  4. Inspect fuel pressure. See the BASIC TESTING article. Repair as needed. If fuel pressure is okay, inspect fuel injector performance. See the SYSTEM/COMPONENT TESTS article. Replace as needed.
  5. If all injectors are okay, inspect EGR system. See the SYSTEM/COMPONENT TESTS article. Repair as needed. If EGR system is okay, inspect MAP sensor and CTS. See the SYSTEM/COMPONENT TESTS article. Replace as needed. If both components are okay, also inspect engine compression, valve clearance and valve timing. See the BASIC TESTING article.
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