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DTC P0172 - Fuel Injection System Function-Rich Side

  1. Check Exhaust/Intake Air Leak

    Start engine and run at idle. Listen for exhaust air leaks before three way catalyst. Listen for intake air leaks after MAF sensor. If any leaks are detected, repair or replace appropriate parts or systems as required. If no leaks are detected, go to next step.

  2. Check Front Heated O2 Sensor

    Turn ignition switch to OFF position. Disconnect front heated O2 sensor and ECM harness connectors. See Figure and Figure . Using an ohmmeter, check continuity between ECM harness connector terminal No. 46 and front heated O2 sensor harness connector terminal No. 2 (White wire). See Figure. If no continuity exists, repair open in White wire. If continuity exists, check continuity between ECM harness connector terminal No. 46 (White wire) and ground. If continuity exists, repair shorted White wire. If no continuity exists, go to next step.

  3. Check Fuel Pressure

    Turn ignition to switch to OFF position. Relieve fuel pressure. See the REMOVE/INSTALL/OVERHAUL article. Install fuel pressure gauge. With ignition on, fuel pressure should be about 43 psi (3.0 kg/cm2 ). At idle, fuel pressure should be about 34 psi (2.4 kg/cm2 ). If fuel pressure is not as specified, check for fault in fuel pump and related circuitry. If fuel pressure is okay, inspect MAF sensor. See DTC P0100  - MASS AIR FLOW sensor and go to next step.

  4. Check Function Of Injectors

    Turn ignition switch to ON position. Using a voltmeter, check voltage between ground and ECM connector terminals No. 102 (White/Black wire), 104 (White/Red wire), 107 (White/Blue wire) and 109 (White/Green wire). See Figure. If battery voltage does not exist, repair fault in wires as required. If battery voltage exists at all terminals, go to next step.
  5. Turn ignition switch to OFF position. Allow engine to cool. Remove injector assembly, keeping fuel hose and all injectors connected to injector gallery. Disconnect all injector harness connectors. Disconnect ignition coil harness connector. Crank engine for about 3 seconds. Verify no fuel drips from injectors. If any injector drips fuel, replace faulty injector. If no injectors drip fuel, go to next step.
  6. Check ECM pins and terminals for damage and check connection of ECM harness connector. Reconnect ECM harness connector and retest.
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