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P0174-FUEL SYSTEM 2/1 LEAN (CONTINUED) 2. CHECKING FUEL PRESSURE WARNING: The fuel system is under a constant pressure (even with the engine off). Before testing or ser- Ignition on, engine not running. With the scan tool, actuate the ASD Fuel System test and observe the fuel pressure gauge. NOTE: Fuel pressure specification is 407 KPa +/- 34 KPa (59 psi +/- 5 psi). CAUTION: Stop All Actuations. Choose a conclusion that best matches your fuel pressure reading. Within Specification Go To 3 Above Specification Replace the fuel filter/pressure regulator. Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE) Below Specification Go To 12 3. O2 SENSOR OPERATION Start the engine. Allow the engine to reach normal operating temperature. NOTE: If one of the O2 Sensor’s Signal or Return circuit is shorted to ground the scan tool will display all NOTE: If one of the O2 Sensor Signal or Return circuits are shorted to voltage, the scan tool will display all NOTE: After the repairs have been made, verify proper O2 Sensor operation. If all the O2 Sensor voltage Is the voltage switching between 2.5 and 3.4 volts? Yes >> Go To 4 No >> Go To 8 HB ENGINE ELECTRICAL DIAGNOSTICS 9 - 243 |