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P0172-FUEL SYSTEM 1/1 RICH (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) 3. O2 SENSOR OPERATION Start the engine. Allow the engine to reach normal operating temperature. NOTE: If one of the O2 Sensors Signal or Return circuit is shorted to ground or voltage, all the other O2 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 9 4. 1/1 O2 SENSOR HEATER OPERATION Turn the ignition off. NOTE: Wait a minimum of 10 minutes to allow the O2 Sensor to cool down before continuing the test. Allow With the scan tool, perform the 1/1 O2 Heater Test. With the scan tool, monitor the O2 Sensor voltage while performing the Heater test for at least 2 minutes. Does the voltage stay above 4.5 volts during the Heater test? Yes >> Replace the O2 Sensor. Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE) No >> Go To 5 9 - 232 ENGINE ELECTRICAL DIAGNOSTICS WK |