P0140
DTC P0140CIRCUIT 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 of the exhaust stream. When the vehicle is first started the powertrain control module (PCM) operates in an Open Loop mode, ignoring the HO2S signal voltage when calculating the air-to-fuel ratio. The PCM supplies the HO2S with a reference, or bias, voltage of about 450 mV. The HO2S generates a voltage within a range of 0-1,000 mV that fluctuates above and below bias voltage once the sensor reaches operating temperature. High HO2S voltage output indicates a rich fuel mixture; low HO2S voltage output indicates a lean mixture. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature and provide an accurate voltage signal. The HO2S 2 is used for post catalyst monitoring. If the PCM detects that the HO2S 2 voltage remains at or near the bias voltage, DTC P0140 will set for bank 1 sensor 2, or DTC P0160 will set for bank 2 sensor 2.
Each HO2S 2 has the following circuits:
- The HO2S 2 high signal circuit
- The HO2S 2 low signal circuit
- The HO2S 2 ignition 1 voltage circuit
- The HO2S 2 heater low control circuit
CONDITIONS FOR RUNNING THE DTC
- DTCs P0036, P0056, P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0125, P0128, P0201-P0206, P0442, P0443, P0446, P0449 are not set.
- The Engine Run Time parameter is longer than 2 minutes.
- The Start Up ECT parameter is less than 35°C (95°F).
- The Start Up IAT parameter is less than 35°C (95°F).
- The difference between Start Up ECT and Start Up IAT parameters is less than 6°C (10.8°F).
- The TP Indicated Angle parameter changes more than 5 percent at least 2 times.
- The Loop Status parameter is closed.
- The ignition voltage is between 9-18 volts.
- The HO2S heater is not being commanded by the scan tool.
CONDITIONS FOR SETTING THE DTC
The PCM detects that the HO2S 2 signal voltage remains between 390-520 mV for more than 108 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
Steps 1 - 5:
Steps 6 - 10:
