P0140

CIRCUIT DESCRIPTION

Engine Control Schematics: Heated Oxygen Sensors (HO2S):

The HO2S is a sensor used to detect oxygen-content in the exhaust. The PCM supplies the sensor with a signal circuit and a ground circuit. The PCM supplies a bias voltage between the circuits. The sensor varies the voltage based on the oxygen content in the exhaust. When the exhaust stream is lean (more oxygen), the sensor produces a low voltage signal. When the exhaust stream is rich (less oxygen), the sensor produces a high voltage signal.

The PCM monitors the HO2S signal during closed loop. To correct for rich or lean conditions, the PCM adjusts the injector pulse width. If HO2S bank 1 sensor 2 remains at, or near the bias voltage for a calibrated period of time, DTC P0140 will set.

CONDITIONS FOR RUNNING THE DTC
^ No TP sensor, MAF sensor, MAP sensor, IAT sensor, ECT sensor, HO2S heater, EVAP system, AIR system (if equipped), fuel injector, EGR system DTCs are set.
^ Engine run time is more than 200 seconds (3 minutes).
^ TP angle is between 3 percent and 25 percent.
^ A change in TP angle more than 5 percent occurs at least 7 times.
^ System voltage is between 9 and 18 volts.
^ Closed loop fuel control is enabled.
^ Air fuel ratio is between 14.4 and 14.9
^ Catalyst test inactive.
^ AIR test inactive.
^ The condition above are met for 5 seconds.

CONDITIONS FOR SETTING THE DTC
HO2S bank 1 sensor 2 signal voltage remain within 400 and 500 mV for approximately 190 seconds (approximately 3 minutes).

ACTION TAKEN WHEN THE DTC SETS
^ The PCM illuminates the Malfunction Indicator Lamp (MIL) during the second consecutive trip in which the diagnostic test runs and fails.
^ The PCM stores the conditions present when the DTC set as Freeze Frame and Fail Records data.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The PCM will turn the MIL OFF after the third consecutive trip in which the diagnostic runs and passes
^ The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
^ The DTC can be cleared by using the scan tool Clear DTC Information function.

DIAGNOSTIC AIDS

NOTE: Refer to HO2S wire repair notice in Service Precautions.

For intermittent conditions, refer to Symptoms. Intermittent Conditions

TEST DESCRIPTION

Steps 1 - 9:

Steps 10 - 13: