P0133

CIRCUIT 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 in Closed Loop. A high HO2S voltage output indicates a rich fuel mixture. A 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 PCM monitors the HO2S rich-to-lean and lean-to-rich transition time. This DTC will set if the HO2S voltage average response time is too slow.

Each HO2S has the following circuits:
^ HO2S 1 high signal
^ HO2S 1 low signal
^ HO2S 1 heater ignition 1 voltage
^ HO2S 1 heater ground

CONDITIONS FOR RUNNING THE DTC
^ DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0410, P0440, P0442, P0443, P0446, P0449, or P1441 are not set.
^ The PCM has commanded Closed Loop for at least 60 seconds.
^ The engine speed is between 1,000-3,000 RPM.
^ The engine coolant temperature (ECT) is more than 50°C (122°F).
^ The mass airflow (MAF) is between 13-32 g/s.

CONDITIONS FOR SETTING THE DTC
The DTC will set if either of the following conditions are present:
^ The HO2S 1 rich-to-lean transition time takes longer than 145 milliseconds.
^ The HO2S 1 lean-to-rich transition time takes longer than 135 milliseconds.

ACTION TAKEN WHEN THE DTC SETS
^ The PCM illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
^ The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the failure records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the operating conditions to the Freeze Frame and updates the Failure Records.

CONDITIONS FOR CLEARING THE DTC
^ The PCM turns OFF the MIL after 3 consecutive ignition cycles that the diagnostic runs and passes.
^ A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
^ A DTC stored in history clears after 40 warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
^ Use the scan in order to clear the DTCs.

TEST DESCRIPTION

Steps 1-8:

Steps 9-16:

The numbers below refer to the step numbers on the diagnostic table.
2. A normally functioning HO2S 1 voltage signal will fluctuate above and below the bias voltage amount.
4. A voltage reading other than bias voltage in this step indicates a short circuit condition in the high signal circuit.
5. A voltage reading higher than the specified amount indicates an open circuit condition in the HO2S 1 signal circuits.
6. This step checks for an open circuit condition in the signal circuits, independent of the PCM.
8. This step verifies that there are functional HO2S 1 heater power and ground circuits.
10. The conditions listed in the table may contribute to the failure of the HO2S. The conditions listed apply only to this type of failure.