P0140
DTC P0140
Circuit Description
Heated oxygen sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content in the exhaust stream. The HO2S must reach operating temperature to provide an accurate voltage signal. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature. The powertrain control module (PCM) supplies the HO2S with a reference, or bias, voltage of about 450 mV. When the engine is first started the PCM operates in open loop, ignoring the HO2S voltage signal. Once the HO2S reaches operating temperatures and Closed Loop is achieved, the HO2S generates a voltage within a range of 0-1,000 mV that fluctuates above and below bias voltage. High HO2S voltage indicates a rich exhaust stream. Low HO2S voltage indicates a lean exhaust stream.
If the PCM detects that the HO2S 2 voltage remains within the bias voltage range, DTC P0140 will set.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0140 HO2S Circuit Insufficient Activity Sensor 2
Conditions for Running the DTC
* DTCs P0036, P0068, P0069, P0097, P0098, P0101, P0102, P0103, P0106, P0107, P0108, P0117, P0118, P0120, P0121, P0141, P0201, P0202, P0203, P0204, P0220, P0442, P0443, P0446, P0449, P0452, P0453, P0461, P0496, P1516, P2101, P2135, or P2176 are not set.
* The Engine Coolant Temperature (ECT) Sensor parameter is more than 70°C (158°F).
* The Ignition 1 Signal parameter is between 11-18 volts.
* The Engine Run Time parameter is more than 200 seconds.
* The Loop Status parameter is closed.
* The Throttle Position (TP) Indicated Angle parameter changes more than 1 percent at least 3 times.
* The catalyst diagnostic is not active.
* DTC P0140 runs once per drive cycle when the above conditions have been met.
Conditions For Setting The DTC
* The PCM detects that the HO2S 2 parameter is between 425-475 mV.
* DTC P0140 sets within 100 seconds when the above conditions are met.
Action Taken When the DTC Sets
* The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
* The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.
Conditions for Clearing the MIL/DTC
* The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
* A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
* A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
* Clear the MIL and the DTC with a scan tool.
Test
