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Home >> Mitsubishi >> 2002 >> Lancer ES, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0300: Random/Multiple Cylinder Misfire Detected >> Diagnostic Procedure
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Diagnostic Procedure

CAUTION: To prevent damage to scan tool, always turn ignition switch to LOCK position before connecting or disconnecting scan tool.
  1. Using scan tool, check crankshaft position sensor. Connect scan tool to data link connector. Start and operate engine at idle. Set scan tool to the data reading mode for data list item 22: CRANKSHAFT POSITION SENSOR. Check the waveform of the crankshaft position sensor while keeping the engine speed constant. The pulse width should be constant. Turn ignition switch to LOCK position. If the sensor is operating properly, go to next step. If the sensor is not operating properly, go to DTC P0335: CRANKSHAFT POSITION SENSOR CIRCUIT  .
  2. Using scan tool, check long-term fuel compensation (trim). Start and operate engine at idle. Set scan tool to the data reading mode for data list item 81, LONG-TERM FUEL COMPENSATION (TRIM). The fuel trim should be between -12.5 and 12.5 when the load is 2500 RPM (during closed loop) after the engine is at operating temperature. Turn ignition switch to LOCK position. If the specification is as specified, go to next step. If the specification is not as specified, go to DTC P0171: SYSTEM TOO LEAN  or DTC: P0172: SYSTEM TOO RICH  .
  3. Using scan tool, check short-term fuel compensation (trim). Start and operate engine at idle. Set scan tool to the data reading mode for data list item 82: SHORT-TERM FUEL COMPENSATION (TRIM). The fuel trim should be between -25 and 16.8 when the load is 2500 RPM (during closed loop) after the engine is at operating temperature. Turn ignition switch to LOCK position. If the fuel trim is as specified, go to next step. If the fuel trim is not as specified, go to DTC P0171: SYSTEM TOO LEAN  or DTC: P0172: SYSTEM TOO RICH  .
  4. Check each ignition coil for spark. Remove intake manifold. Remove spark plug and connect to spark plug cable. Ground spark plug side electrode securely. When engine is cranked, spark plug should spark. If spark does not exist, go to next step. If spark exists, go to step  7 .
  5. Check that spark plug is not burned, insulator is not damaged, and that plug is not seized. If cleaning is required due to carbon deposits, etc., clean using a spark plug cleaner or wire brush, etc. Check spark plug gap using a plug gap gauge, and adjust if not 0.039-0.043" (1.0-1.1 mm). If spark plug is in good condition, go to next step. If spark plug is not in good condition, replace the faulty spark plug. After replacing spark plug, go to step  13 .
  6. Check spark plug cable. Check boot and coating for cracks. Measure resistance. Limit is 19 k/ohms maximum. If resistance is as specified, check ignition system. See IGNITION CHECKS in BASIC DIAGNOSTIC PROCEDURES article. If resistance is not as specified, replace faulty spark plug cable. After replacing spark plug cable, go to step  13 .
  7. Disconnect injector connector. Measure resistance between each injector No. 1 and 2. Standard value is 13-16 ohms [at 68°F (20°C)]. If resistance is as specified, go to next step. If resistance is not as specified, replace the faulty injector. After replacing injector, go to step  13 .
  8. Check injector connector (B-17, B-18, B-20, B-22) for damage. If connector is in good condition, go to next step. If connector is not in good condition, repair or replace as necessary. After repairs, go to step  13 .
  9. Check ECM harness connector C-121 (M/T) or PCM harness connector C-120 (A/T) for damage. If connector is in good condition, go to next step. If connector is not in good condition, repair or replace as necessary. After repairs, go to step  13 .
  10. Check for harness damage between injector connector and ECM harness connector (M/T) or PCM harness connector (A/T). See INJECTOR CONTROL CIRCUIT IDENTIFICATION  table. If wiring harness is in good condition, go to next step. If wiring harness is not in good condition, repair as necessary. After repairs, go to step  13 .
  11. Check the following items:
    • Skipped timing belt teeth.
    • Compression.
    • EGR valve.

    If there are no abnormalities, go to next step. If there are any abnormalities, repair or replace as necessary. After repairs, go to step  13 .

  12. Replace fuel injector. Carry out a test drive with the drive cycle pattern. See OTHER MONITOR  under VERIFYING REPAIRS. Check for DTCs. If DTC P0300 is output, replace the ECM or PCM. After replacing ECM or PCM, go to next step. If DTC P0300 is not output, inspection is complete.
  13. Test the OBD-II drive cycle. Carry out a test drive with the drive cycle pattern. See OTHER MONITOR  under VERIFYING REPAIRS. Check for DTCs. If DTC P0300 is output, repeat diagnosis. If DTC P0300 is not output, inspection is complete.
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