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P0174-FUEL SYSTEM 2/1 LEAN (CONTINUED) 4. 2/1 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 NOTE: Perform the following test on all O2 Sensors. With a scan tool, actuate the 2/1 O2 Heater Test. With the scan tool, monitor 2/1 O2 Sensor voltage for at least 2 minutes. Does the voltage stay above 4.5 volts? Yes >> Replace the 2/1 O2 Sensor. Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE) No >> Go To 5 5. MAP SENSOR OPERATION Turn the ignition off. Connect a Vacuum Gauge to a Manifold Vacuum source. Start the engine. Allow the engine to idle. NOTE: If engine will not idle, maintain a constant RPM above idle. Is the scan tool reading within 1 ( of the Vacuum Gauge reading? Yes >> Go To 6 No >> Replace the MAP Sensor. Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE) 6. ECT SENSOR OPERATION NOTE: For this test to be valid, the thermostat must be operating correctly. NOTE: This test works best if performed on a cold engine (cold soak). With the scan tool, read the Engine Coolant Temperature (ECT) Sensor value. If the engine was allowed to sit NOTE: If engine coolant temperature is above 82°C (180°F), allow the engine to cool until 65°C (150°F) is During engine warm-up, monitor the ECT Sensor value. The temperature value change should be a smooth tran- Did the ECT value increase smoothly and did it reach at least 180°F (82°C)? Yes >> Go To 7 No >> Replace the Engine Coolant Temperature Sensor. Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE) 9 - 240 ENGINE ELECTRICAL DIAGNOSTICS WK |