P0140

CIRCUIT DESCRIPTION
The Powertrain Control Module (PCM) supplies a voltage of about 450 mV between the HO2S high and low signal circuits. The oxygen sensor varies the voltage over a range from about 1,000 mV when the exhaust is rich, down through about 10 mV when the exhaust is lean.

The PCM monitors and stores the Heated Oxygen Sensor (HO2S) voltage information. The PCM evaluates the HO2S voltage samples in order to determine the amount of time the HO2S voltage was out of range. The PCM compares the stored HO2S voltage samples taken within each sample period and determines if majority of the samples are out of the operating range.

The PCM monitors the HO2S voltage and detects if the voltage goes out of the bias range. If the PCM does not detect the voltage went out of the bias range, a DTC sets.

CONDITIONS FOR RUNNING THE DTC
^ DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0117, P0118, P121, P0122, P0123, P0135, P0141, P0155, P0161, P0200, P0300, P0410, P0440, P0442, P0446, P0452, P0453, P1258, P1415, P1416, or P1441 are not set.
^ The engine run time is more than 409 seconds.
^ The ignition 1 signal is between 9-18 volts.
^ The loop status is Closed.
^ The secondary Air Injection (AIR) and the catalyst diagnostics are not active.

CONDITIONS FOR SETTING THE DTC
^ The HO2S signal voltage is steady between 409-489 mV for 145 seconds.
^ The Throttle Position (TP) changes more than 5 percent within 1 second, 6 times.

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.
^ Use a scan tool in order to clear the MIL and the DTC.

TEST DESCRIPTION

Steps 1-7:

Steps 8-13:

The numbers below refer to the step numbers on the diagnostic table.
2. Before you perform this test, the engine must be at the normal operating temperature.
3. The Freeze Frame/Failure Records may help to locate an intermittent condition. If you cannot duplicate the DTC, the information in the Freeze Frame/Failure Records can help to determine how many miles have occurred since the DTC set. The Fail Counter and the Pass Counter can also determine how many ignition cycles have occurred since the diagnostic reported a pass and/or a fail. In order to isolate when the DTC failed, operate the vehicle within the same Freeze Frame conditions that the PCM recorded. These conditions include the RPM, the vehicle load, the vehicle speed, and the temperature.
4. If the scan tool indicates the HO2S voltage goes below 200 mV, the HO2S circuits and PCM are OK.
5. This step verifies whether the HO2S low signal circuit from the PCM is OK.
6. This step verifies whether the HO2S low signal circuit from the PCM is OK. A voltage indicates that the PCM and wiring are OK.
7. Disconnecting the PCM allows using a DMM in order to test the circuit continuity. This procedure helps to locate a circuit that is open or shorted.