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Home >> Nissan-Datsun >> 2003 >> Sentra Limited >> Repair and Diagnosis >> External Pages >> Different car >> Section 40 (Engine Controls - Self-Diagnostics - 2.5) >> Diagnostic Tests >> DTC P0300, DTC P0301, DTC P0302, DTC P0303 &/Or DTC P0304 >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2002 Nissan Sentra. However, it is still accessible from the selected car via links, so may be relevant.
  1. Start engine and let idle. Check for intake leaks. Stop engine and visually inspect exhaust system, 3-way catalyst and muffler for damage. Repair intake or exhaust system as necessary and retest system. If intake and exhaust systems are okay, go to next step.
  2. Start engine and let idle. Individually, disconnect fuel injector harness connectors. If engine speed momentarily drops, go to step  5. If engine speed does not momentarily drop, listen to each fuel injector. If all injectors click, go to next step. If any injector does not click, repair injector or circuit and retest system. See SYSTEM & COMPONENT TESTING article.
  3. Turn ignition off. Check for spark at misfiring cylinder(s). If spark is detected, go to step  5. If no spark is detected, go to next step.
  4. Check spark plug wires. Spark plug wire resistance should be 4.15-5.61 k/ohms per foot at 77°F (25°C). If problem exists, replace spark plug and/or spark plug wires as necessary, then retest system. If spark plug wires are okay, check distributor cap, rotor, ignition coil, power transistor and related circuits. See SYSTEM & COMPONENT TESTING article. Repair ignition system as necessary and retest system. If ignition system is okay, go to next step.
  5. Check spark plugs. Replace spark plus as necessary and retest system. If spark plugs are okay, check engine compression. See BASIC DIAGNOSTIC PROCEDURES article. Standard specification is 178 psi (12.2 kg/cm2 ). Minimum specification is 149 psi (10.3 kg/cm2 ). If compression is not within specification, repair engine as necessary and retest system. If compression is okay, go to next step.
  6. Check fuel pressure. See BASIC DIAGNOSTIC PROCEDURES article. Fuel pressure should be 34 psi (2.4 kg/cm2 ) with vacuum hose connected to fuel pressure regulator. Fuel pressure should be 43 psi (3.0 kg/cm2 ) with vacuum hose disconnected from fuel pressure regulator. If fuel pressure is not as specified, repair fuel system as necessary. If fuel pressure is as specified, go to next step.
  7. Check ignition timing. See ON-VEHICLE ADJUSTMENTS article. If ignition timing is incorrect, adjust as necessary and retest system. If ignition timing is okay, go to next step.
    8. CAUTION: DO NOT use ECM ground terminals when measuring voltage.
  8. Ensure engine is at normal operating temperature. Measure voltage between ground and ECM terminal No. 62 (White wire) by backprobing. See Figure and Figure . Increase engine speed to 2000 RPM. The following conditions should exist:
    • Voltage cycles from 0-0.3 volt to 0.6-1.0 volt and back more than 5 times within 10 seconds.
    • Maximum voltage is more than .6 volt at least once.
    • Minimum voltage is less than .3 volt at least once.
    • Voltage never exceeds one volt.

    If operation is as specified, go to next step. If operation is not as specified, replace HO2S and retest system.

  9. Turn ignition off. Connect scan tool to Data Link Connector (DLC). Using scan tool, check MAF sensor signal. At idle, value should be 2.5-5.0 gm/sec. At 2500 RPM, value should be 7.1-12.5 gm/sec. If values are as specified, go to next step. If values are not as specified, repair MAF sensor or circuit. See DTC P0101, DTC P0102, DTC P0103 & P1102 .
  10. Check for possible causes of rough idle. See ROUGH IDLE under SYMPTOMS in TROUBLESHOOTING - NO CODES article. Repair as necessary and retest system. Clear any DTCs that may have been set by performing test. Problem may be intermittent. See INTERMITTENTS in TROUBLESHOOTING - NO CODES article.
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