P0140

CIRCUIT DESCRIPTION
The Heated Oxygen Sensor (HO2S) is a sensor used to detect the oxygen content in the exhaust. The Powertrain Control Module (PCM) supplies the sensor with a signal circuit and a ground circuit. The PCM supplies a bias voltage between the circuits. The sensor varies the voltage based on the oxygen content in the exhaust. When the exhaust stream is lean, indicating more oxygen, the sensor produces a low voltage signal. When the exhaust stream is rich, indicating less oxygen, the sensor produces a high voltage signal. The PCM monitors the HO2S signal during Closed Loop. In order to correct for rich or lean conditions, the PCM adjusts the injector pulse width.

CONDITIONS FOR RUNNING THE DTC
^ DTCs P0030, P0036, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0135, P0141, P0171 or P0174, P0172 or P0175, P0201-P0208, P0401, P0403, P0404, P0405, P0410, P0412, P0418, P0440, P0442, P0443, P0446, P0449, P0560-P0563, P1106, P1107, P1111, P1112, P1114, P1115, P1121, P1122, P1404, P1415, or P1416 are not set.
^ The system voltage is between 9-18 volts.
^ The engine is running for 200 seconds.
^ Closed Loop is enabled.
^ The Exhaust Gas Recirculation (EGR) flow diagnostic test is not active.
^ The Secondary Air Injection (AIR) diagnostic test is not active.
^ The catalyst diagnostic test is not active.

CONDITIONS FOR SETTING THE DTC
The HO2S bank 1 sensor 2 signal voltage remains within 400-500 mV for approximately 80 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.
^ Use a scan tool in order to clear the MIL and the DTC.

DIAGNOSTIC AIDS

NOTE:
^ Refer to Heated Oxygen Sensor (HO2S) Wire Repair Notice in Service Precautions.
^ Refer to J 35616-A Connector Test Adapter kit Notice in Service Precautions.

Check for the following conditions:
^ Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection. Refer to Testing for Intermittent and Poor Connections in Diagrams.
^ A damaged harness-Inspect the wiring harness for damage. If the harness appears to be OK, observe the scan tool while moving connectors and wiring harnesses related to HO2S bank 1 sensor 2. A change in the display will indicate the location of the malfunction. Refer to Testing for Intermittent and Poor Connections in Diagrams.
^ For intermittent conditions, refer to Symptoms - Computer and Control Systems. Symptom Related Diagnostic Procedures

Reviewing the Failure Records vehicle mileage since the diagnostic test last failed may assist in diagnosing the condition. The information may help determine how often the condition that set the DTC occurs.

TEST DESCRIPTION

Steps 1-8:

Steps 9-11:

The numbers below refer to the step numbers on the diagnostic table.
5. Check the HO2S bank 1 sensor 2 wiring, and the PCM's response. With the harness connector terminals jumpered together, the scan tool should display an HO2S bank 1 sensor 2 voltage below 150 mV.
9. This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.