DTC P0171 FUEL INJECTION SYSTEM FUNCTION (LEAN SIDE) - Diagnostic Procedure (Cont'd)

2. CHECK FOR INTAKE AIR LEAK Listen for an intake air leak after the mass air flow sensor.

3. CHECK HEATED OXYGEN SENSOR 1 (FRONT) CIRCUIT 1. Turn ignition switch "OFF". 2. Disconnect heated oxygen sensor 1 (front) harness connector and ECM harness connector. 3. Check harness continuity between ECM terminal 12 and heated oxygen sensor 1 (front) harness connector terminal 1. Refer to wiring diagram. Continuity should exist. 4. Check harness continuity between ECM terminal 12 (or terminal 1) and ground. Continuity should not exist. 5. Also check harness for short to ground and short to power.

4. CHECK FUEL PRESSURE 1. Release fuel pressure to zero. Refer to EC-7024. 2. Install fuel pressure gauge and check fuel pressure. At idling: When fuel pressure regulator valve vacuum hose is connected. 235 kPa (2.35 bar, 2.4 kg/cm^2, 34 psi) When fuel pressure regulator valve vacuum hose is disconnected. 294 kPa (2.94 bar, 3.0 kg/cm^2, 43 psi)

5. DETECT MALFUNCTIONING PART Check the following. - Fuel pump and circuit Refer to EC-7236. - Fuel pressure regulator Refer to EC-7025. - Fuel lines Refer to "ENGINE MAINTENANCE" in MA section. - Fuel filter for clogging Repair or replace.