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Home >> Nissan-Datsun >> 2003 >> Sentra Limited >> Repair and Diagnosis >> External Pages >> Different car >> Section 112 (Engine Controls Self-Diagnostics - Pathfinder) >> Diagnostic Tests >> DTC P0300, DTC P0301, DTC P0302, DTC P0303, DTC P0304, DTC P0305 Or DTC P0306 >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2003 Nissan Pathfinder. However, it is still accessible from the selected car via links, so may be relevant.
  1. Start engine and let it idle. Check for intake air leaks. Check PCV hose. Stop engine and visually inspect exhaust system, 3-way catalyst and muffler for blockage. If a problem is found, repair as necessary. If no problems are found, go to next step.
  2. If using CONSULT-II, go to next step. If using generic scan tool, go to step  4.
  3. Perform POWER BALANCE in ACTIVE TEST mode with CONSULT-II. If there is any cylinder which does not produce a momentary engine speed drop, go to step  6. If all cylinders produce a momentary engine speed drop, go to step  5.
  4. Start engine and let it idle. Individually, disconnect and reconnect fuel injector harness connectors. If there is any cylinder which does not produce a momentary engine speed drop, go to step  6. If all cylinders produce a momentary engine speed drop, go to next step.
  5. Using an appropriate listening device, listen to each fuel injector. If every injector clicks, go to next step. If any injector does not click, repair injector or circuit as necessary. See FUEL SYSTEM in SYSTEM & COMPONENT TESTING article.
  6. Turn ignition off. Disconnect spark plug from coil. Connect a known-good spark plug. Place end of spark plug against a suitable ground and crank engine. If spark is detected, go to next step. If no spark is detected, check ignition coil, power transistor and their related circuits. See SYSTEM & COMPONENT TESTING article.
  7. Remove spark plugs. Inspect spark plugs for fouling or other damage. If problem is found, repair or replace spark plugs as necessary. If spark plugs are okay, go to next step.
  8. Check compression. See MECHANICAL INSPECTION under PRELIMINARY INSPECTION & ADJUSTMENTS in BASIC DIAGNOSTIC PROCEDURES article. If compression is as specified, go to next step. If compression is not as specified, check pistons, piston rings, valves, valve seats and cylinder head gaskets. If problem is found, repair as necessary.
  9. Check fuel pressure. See FUEL SYSTEM in BASIC DIAGNOSTIC PROCEDURES article. If fuel pressure is okay, go to next step. If fuel pressure is not okay, repair fuel system as necessary. See FUEL SYSTEM in SYSTEM & COMPONENT TESTING article.
  10. Check target idle speed and ignition timing. See IDLE SPEED, IGNITION TIMING & IDLE MIXTURE RATIO ADJUSTMENT in ON-VEHICLE ADJUSTMENTS article. If ignition timing and target idle speed are okay, go to next step. If ignition timing or target idle speed is not okay, perform BASIC INSPECTION. See ON-VEHICLE ADJUSTMENTS article.
  11. Start engine and warm to normal operating temperature. If using CONSULT-II, go to next step. If using generic scan tool, go to step  13.
  12. Select MANU TRIG and HI SPEED in DATA MONITOR mode with CONSULT- II. Select HO2S 1 (B1)/(B2) and HO2S 1 MNTR (B1)/(B2). Hold engine speed at 2000 RPM under no load. Touch RECORD on CONSULT-II screen. The following should occur:
    • HO2S 1 MNTR (B1)/(B2) in DATA MONITOR mode changes from RICH to LEAN to RICH 5 times in 10 seconds.
    • HO2S 1 (B1)/(B2) voltage is more than 0.6V at least once.
    • HO2S 1 (B1)/(B2) voltage is less than 0.3V at least once.
    • HO2S 1 (B1)/(B2) voltage never exceeds 1.0V.
    If operation is as specified, go to step  14. If operation is not as specified, replace appropriate HO2S.
    13. CAUTION: DO NOT use ECM ground terminals when measuring voltage.
  13. Backprobing at ECM, measure voltage between ground and ECM terminal No. 35 (bank 1) or No. 16 (bank 2). See Figure and Figure . Increase engine speed to 2000 RPM. The following should occur:
    • Voltage should cycle from less than 0.3 volt to more than 0.6 volt and back more than 5 times within 10 seconds.
    • Maximum voltage should be more than 0.6 volt at least once.
    • Minimum voltage should be less than 0.3 volt at least once.
    • Voltage should never exceed one volt.
    If operation is as specified, go to next step. If operation is not as specified, replace appropriate HO2S 1.
  14. Select DATA MONITOR with CONSULT- II or MODE 1 with scan tool, and read Mass Airflow (MAF) signal. MAF reading should be 2-6 grams per second at idle and 7-20 grams per second at 2500 RPM. If MAF reading is as specified, go to step  16. If MAF reading is not as specified, go to next step.
  15. Check connectors for rusted terminals or loose connections in MAF sensor circuit or engine grounds. See DTC P0102 OR P0103 . If a problem is found, repair as necessary.
  16. Check for possible causes of rough idle. See ROUGH IDLE under SYMPTOMS in TROUBLE SHOOTING - NO CODES article. If a problem is found, repair as necessary. If a problem is not found, go to next step.
  17. Some tests that were performed may cause a 1st trip DTC to set. Clear 1st trip DTC as necessary. Go to next step.
  18. No problem is indicated at this time. Problem may be intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES article.
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