P0140

CIRCUIT DESCRIPTION
Oxygen sensors (O2S) are used for fuel control and post catalyst monitoring. Each O2S compares the oxygen content of the surrounding air with the oxygen content in the exhaust stream. The O2S must reach operating temperature to provide an accurate voltage signal. A heating element in O2S 2 minimizes the time required for the sensor to reach operating temperature. The powertrain control module (PCM) supplies the O2S with a reference, or bias, voltage of about 450 mV. When the engine is first started the PCM operates in open loop, ignoring the O2S voltage signal. Once the O2S reaches operating temperature and Closed Loop is achieved, the O2S generates a voltage within a range of 0-1,000 mV that fluctuates above and below bias voltage. High O2S voltage indicates a rich exhaust stream. Low O2S voltage indicates a lean exhaust stream. If the PCM detects that HO2S voltage remains within the bias voltage range, DTC P0140 will set.

CONDITIONS FOR RUNNING THE DTC
- DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0171, P0172, P0201-P0204, P0300, P0301-P0304, P0336, P0440, P0446, P0452, P0453, P0506, P0507, P0601, P0602, or P1441 are not set.
- The Air Flow Calculated parameter is more than 5.5 g/s for 70 seconds.
- The ECT Sensor parameter is more than 70°C (158°F).
- The Loop Status parameter is closed.
- The TP Sensor parameter is between 8-56 percent.
- The MAP Sensor parameter is more than 25 kPa.
- The Fuel Level Sensor parameter is more than 10 percent.
- The Ignition 1 Signal parameter is more than 10 volts.

CONDITIONS FOR SETTING THE DTC
The PCM detects that the HO2S 2 parameter is between 425-460 mV for 125 seconds.

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 DESCRIPTION

Steps 1-4:

Steps 5-7:

Steps 8-12:

Steps 13-14:

The numbers below refer to the step numbers on the diagnostic table.
5. The specified value is what is measured on a correctly operating system.
6. The specified value is what is measured on a correctly operating system.