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Home >> Nissan-Datsun >> 2003 >> Sentra Limited >> Repair and Diagnosis >> External Pages >> Different car >> Section 39 (Engine Controls - Self-Diagnostics - 1.8L - XE, GXE) >> Diagnostic Tests >> DTC P0172 Or DTC DTC P0175 >> 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.
NOTE: For circuit wiring diagram, see Figure or Figure . For connector identification and locations, see CONNECTOR IDENTIFICATION  .

  1. Check For Exhaust Leak

    Start engine and let it idle. Listen for exhaust leak before 3-way catalyst. If problem is found, repair as necessary. Perform DTC CONFIRMATION TEST  to verify repair. If problem is not found, go to next step.

  2. Check HO2S1 Signal Circuits

    Disconnect appropriate HO2S1 harness connector. See Figure . Disconnect ECM harness connector. See Figure . Check continuity between HO2S1 harness connector terminal No. 2 and ECM harness connector terminal No. 94 (on bank 1) or No. 62 (on bank 2). See Figure or Figure . Continuity should exist. Also, check harness for short to ground and short to power. If problem is found, repair as necessary. Perform DTC CONFIRMATION TEST  to verify repair. If problem is not found, go to next step.

  3. Check Fuel Pressure

    Check fuel pressure. See BASIC DIAGNOSTIC PROCEDURES article. Fuel pressure should be about 34 psi (235 kPa) with fuel pressure regulator vacuum hose connected and about 43 psi (294 kPa) with fuel pressure regulator vacuum hose disconnected. If fuel pressure is okay, go to next step. If fuel pressure is not okay, repair fuel system as necessary. Perform DTC CONFIRMATION TEST  to verify repair.

  4. Check MAF Sensor

    Install all removed parts. Using CONSULT-II, select MASS AIR FLOW in DATA MONITOR mode. Using generic scan tool, select MODE 1, and read mass airflow. MAF reading should be 1.4-4.0 g/sec at idle and 5.0-10.0 g/sec at 2500 RPM. If MAF reading is as specified, go to next step. If MAF reading is not as specified, check connectors for rusted terminals or loose connections in the MAF sensor circuit for engine grounds. See DTC P0101, DTC P0102, DTC P0103 OR DTC P1102  . Repair as necessary. Perform DTC CONFIRMATION TEST  to verify repair.

  5. Check Function Of Injectors

    Using CONSULT-II, perform POWER BALANCE in ACTIVE TEST mode. Each circuit should produce a momentary engine speed drop. If not using CONSULT-II, listen to each fuel injector. Clicking noise should be heard from each injector. If operation is as specified, go to next step. If operation is not as specified, diagnose and repair fuel injector circuits. See FUEL SYSTEM in SYSTEM & COMPONENT TESTING article. Perform DTC CONFIRMATION TEST  to verify repair.
    6. NOTE: NEW "O" rings must be used on all fuel injectors once removed.

  6. Check Injectors
    Turn ignition off. Allow engine to cool and ensure no fire hazards exist. Remove injector assembly, keeping fuel hose and all injectors connected to injector gallery. Place a suitable cup under each injector to collect fuel. Disconnect all injector harness connectors. Disconnect all ignition coil harness connectors. Crank engine for 3 seconds. Ensure fuel does not drip from injectors. Replace any injector from which fuel does not spray. Perform DTC CONFIRMATION TEST  to verify repair. If all injectors are okay, go to next step.

  7. Check For Intermittent

    Check for intermittent condition. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES article. Perform DTC CONFIRMATION TEST  to verify repair.
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