P0140

DTC P0140 Heated Oxygen Sensor (HO2S 2) Circuit No Activity Detected (Bank1, Sensor 2) (Catalyst Motor):

Heated Oxygen Sensor (HO2S) (Bank 1, Sensor 2):

CIRCUIT DESCRIPTION
The Vehicle Control Module-A (VCM-A) supplies a voltage of about 0.45 volt between terminals "BL21" and "BL7". (If measured with a 10 megohm digital voltmeter, this may read as low as 0.32 volt.) The Heated Oxygen Sensor (HO2S 2) varies the voltage within a range of about 1 volt if the exhaust is rich, down through about 0.10 volt if exhaust is lean.

The sensor is like an open circuit and produces no voltage when it is below 360°C (600°F).

The HO2S heater provides for faster sensor warm-up which allows the sensor to become active in a shorter period of time and remain active during long extended idle. DTC P0140 determines if the HO2S or the HO2S circuit has developed an open.

DTC P0140 WILL SET WHEN
^ No Throttle Position (TP) sensor DTCs.
^ No Evaporative Emissions (EVAP) System DTCs.
^ No Intake Air Temperature (IAT) sensor DTCs.
^ No Manifold Absolute Pressure (MAP) DTCs.
^ No fuel trim DTCs.
^ No Exhaust Gas Recirculation (EGR) DTCs.
^ "Closed Loop."
^ No Engine Coolant Temperature (ECT) sensor DTCs.
^ Engine run time is greater than 120 seconds.
^ HO2S is between 0.350V and 0.473V.

ACTION TAKEN (VCM-A WILL DEFAULT TO)
With a current DTC set, the Malfunction Indicator Lamp (MIL) (Service Engine Soon) will be turned "ON" after 2 test failures.

DTC P0140 WILL CLEAR WHEN
The VCM-A will turn the MIL "OFF" after three consecutive trips without a fault condition present. A history DTC will be cleared if no fault conditions have been detected for forty warm-up cycles [coolant temperature has risen 22°C (40°F) from start-up coolant temperature and engine coolant temperature exceeds 71°C (160°F) that same ignition cycle] or the Tech 1 clearing feature has been used.

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. If the conditions for setting DTC P0140 exist, the system will not go into "Closed Loop."
2. This will determine if the sensor or the wiring is the cause of DTC P0140.
3. This test checks the continuity of CKT 1670.

DIAGNOSTIC AIDS
An intermittent may be caused by a poor connection, rubbed through wire insulation, or a wire broken inside the insulation.

Check for:
^ Poor connection or damaged harness - Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection, and damaged harness.
^ Faulty HO2S 2 heater or heater circuit - With the ignition "ON," engine "OFF" the HO2S 2 voltage displayed on a Tech 1 should gradually drop to below 0.300 volt, indicating that the heater is working properly. If not, disconnect the HO2S 2 and connect a test light between terminals "C" and "D". If the test light does not light, repair open CKT(s) 150 or 539. If the test light lights, replace HO2S 2.
^ Intermittent test - With Tech 1, monitor HO2S 2 signal voltage while moving related connectors and wiring harness, with warm engine running at part throttle in "Closed Loop." If the failure is induced, the HO2S 2 signal voltage reading will change from its normal fluctuating voltage (above 600 mV and below 300 mV) to a fixed value around 450 mV. This may help to isolate the location of the malfunction.