P0134

CIRCUIT DESCRIPTION
The Heated Oxygen Sensor (HO2S) is a sensor used to detect 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. This Diagnostic Trouble Code (DTC) indicates that the HO2S voltage remained at or near the bias voltage for a calibrated period of time.

CONDITIONS FOR RUNNING THE DTC
^ DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0201-P0208, P0410, P0412, P0418, P0440, P0442, P0443, P0446, P0449, P1106, P1107, P1112, P1114, P1115, P1121, P1122, P1415, or P1416 are not set.
^ The Exhaust Gas Recirculation (EGR) flow diagnostic is not active.
^ The Secondary Air Injection (AIR) diagnostic test is not active.
^ The catalyst diagnostic test is not active.
^ The system voltage is between 9-18 volts.
^ The engine has been running for more than 3 minutes.

CONDITIONS FOR SETTING THE DTC
The HO2S signal voltage remains within 400-500 mV for approximately 1 minute.

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.

For intermittent conditions, refer to Intermittent Conditions. Intermittent Conditions

TEST DESCRIPTION

Steps 1-3:

Steps 4-11:

The numbers below refer to the step numbers on the diagnostic table.
5. With the harness connector terminals jumpered together, the scan tool should display a HO2S voltage below 75 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.