P0133

CIRCUIT DESCRIPTION
The heated oxygen sensor (HO2S) is a sensor designed to create a voltage relative to the oxygen content in the engine exhaust stream. The control module supplies the HO2S with signal high and low circuits. Ignition voltage and ground are supplied to the HO2S heater by independent circuits. The oxygen content of the exhaust indicates when the engine is operating lean or rich. When the HO2S detects that the engine is operating rich, the signal voltage is high, and decreases the signal voltage as the engine runs leaner. This oscillation above and below the bias voltage, sometimes referred to as activity or switching, can be monitored with the HO2S signal voltage.

The HO2S contains a heater that is necessary in order to quickly warm the sensor to operating temperature. The heater also maintains the operating temperature during extended idle conditions. The HO2S needs to be at a high temperature in order to produce a voltage. When the HO2S reaches operating temperature, the control module monitors the HO2S bias, or reference, voltage. The control module also monitors the HO2S signal voltage for Closed Loop fuel control. During normal Closed Loop control operation, the control module will add fuel, or enrich the mixture, when the HO2S detects a lean exhaust content. The control module will subtract fuel, or lean out the mixture, when the HO2S detects a rich exhaust condition.

This diagnostic trouble code (DTC) is designed to detect a HO2S that is lazy or slow when switching from lean to rich or from rich to lean. The DTC is set when the average transition time is too long.

CONDITIONS FOR RUNNING THE DTC
^ DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0131, P0132, P0134, P0135, P0151, P0152, P0154, P0155, P0200, P0300, P0440, P0442, P0446, P0452, P0453, or P1441 are not set.
^ The engine coolant temperature (ECT) is more than 57°C (135°F).
^ The engine run time is more than 160 seconds.
^ The mass air flow (MAF) sensor is between 18-45 g/s.
^ The engine speed is between 1,300-3,000 RPM.
^ The throttle position (TP) is more than 5 percent.
^ The engine is operating in Closed Loop status.
^ The ignition 1 signal is between 9-18 volts.
^ The fuel tank level remaining is more than 10 percent.
^ Intrusive tests are not in progress.
^ The scan tool output controls are not active.
^ The evaporative emissions (EVAP) purge solenoid command is more than 1 percent.
^ The above conditions are met for 100 seconds.

CONDITIONS FOR SETTING THE DTC
The rich-to-lean and lean-to-rich response average time is more than a calibrated value.

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.

DIAGNOSTIC AIDS

IMPORTANT: Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing or replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent water intrusion into the PCM.

^ This diagnostic only runs once per ignition cycle.
^ A malfunction in the HO2S heater circuits causes a DTC to set-Check the HO2S heater circuits for intermittent opens and for poor connections. Refer to Testing for Intermittent and Poor Connections in Diagnostic Aids.
^ An oxygen supply inside the HO2S is necessary for proper operation. The HO2S wires provide the supply of oxygen. Inspect the HO2S wires and the connections for breaks or for contamination. Refer to Heated Oxygen Sensor (HO2S) Wiring Repairs in Diagnostic Aids.
^ Using the Freeze Frame/Failure Records may help to locate an intermittent condition. If you cannot duplicate the DTC, the information included in the Freeze Frame/Failure Records can help to determine how many kilometers miles) since the DTC set. The Fail Counter and the Pass Counter can also help determine how many ignition cycles the diagnostic reported a pass or a fail. In order to isolate when the DTC failed, operate the vehicle within the same Freeze Frame conditions, and refer to Symptoms - Computers and Controls Systems. Symptom Related Diagnostic Procedures

These conditions include
- The RPM
- The vehicle load
- The vehicle speed
- The temperature

TEST DESCRIPTION

Steps 1-4:

Steps 5-11:

Steps 12-20:

The numbers below refer to the step numbers on the diagnostic table.
2. After the HO2S heater is commanded ON, the HO2S heater heats up causing the HO2S signal voltage to either increase or decrease. This indicates that the HO2S heater is OK.
3. If the HO2S voltage is varying outside the specified range, the condition is not present.
5. If the voltage is below the specified value, the high signal circuit, the low reference circuit, and the PCM are OK.
8. The opposite bank HO2S must be disconnected to isolate a short to ground in the HO2S heater high control circuit.
12. Resistance within the specified range indicates the HO2S heater is OK.