GM Service Manual Online
For 1990-2009 cars only

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 in the exhaust stream. The HO2S must reach operating temperature to provide an accurate voltage signal. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature. The powertrain control module (PCM) supplies the HO2S with a reference, or bias, voltage of about 450 mV. When the engine is first started, the PCM operates in Open Loop, ignoring the HO2S voltage signal. Once the HO2S reaches operating temperatures and Closed Loop is achieved, the HO2S generates a voltage within a range of 0-1,000 mV that fluctuates above and below bias voltage. High HO2S voltage indicates a rich exhaust stream. Low HO2S voltage indicates a lean exhaust stream.

This diagnostic will only run once per ignition cycle. The PCM monitors the rich-to-lean and lean-to-rich transition time. A transition is defined as the HO2S voltage changes from above 650 mV to below 450 mV or from below 450 mV to above 650 mV. If the PCM detects that the transition time is too long, DTC P0133 will set.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0133 HO2S Slow Response Bank 1 Sensor 1

Conditions for Running the DTC

    • DTCs P0030, P0068, P0069, P0097, P0098, P0101, P0102, P0103, P0106, P0107, P0108, P0117, P0118, P0120, P0121, P0125, P0128, P0131, P0132, P0134, P0201, P0202, P0203, P0204, P0220, P0300, P0442, P0443, P0446, P0449, P0452, P0453, P0461, P0496, P1133, P1516, P1681, P2101, P2135, or P2176 are not set.
    • The Engine Coolant Temperature (ECT) Sensor parameter is more than 70°C (158°F).
    • The Ignition 1 Signal parameter is between 11-18 volts.
    • The Fuel Level Sensor parameter is more than 10 percent.
    • The Engine Run Time parameter is more than 200 seconds.
    • The Engine Speed parameter is between 1,000-3,500 RPM.
    • The Manifold Absolute Pressure (MAP) Sensor parameter is more than 30 kPa.
    • The Mass Airflow (MAF) Sensor parameter is between 15-50 g/s.
    • The Loop Status parameter is closed.
    • The Throttle Position (TP) Indicated Angle parameter is more than 5 percent.
    • The catalyst test is not active.
    • Traction control is not active.
    • No fuel injectors are disabled.
    • The transmission is not in Park, Reverse, or Neutral.
    • DTC P0133 runs once per drive cycle when the above conditions are met for 2 seconds.

Conditions for Setting the DTC

    • The PCM detects that the HO2S 1 rich-to-lean or lean-to-rich average response time is more than 0.1 second.
    • DTC P0133 sets within 60 seconds when the above condition is met.

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.

Test Description

The number below refers to the step number on the diagnostic table.

  1. If the voltage is varying above and below the specified value, the condition is not present.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

Important: If DTC P0030 or P0135 is set, diagnose those DTCs first. Refer to Diagnostic Trouble Code (DTC) List - Vehicle .

  1. Start the engine.
  2. Allow the engine to reach operating temperature. Refer to Scan Tool Data List .
  3. Operate the engine at 1,500 RPM for 30 seconds.
  4. Observe the Heated Oxygen Sensor (HO2S) 1 parameter with a scan tool.

Is the HO2S 1 parameter varying above and below the specified range?

450-650 mV

Go to Step 3

Go to Step 4

3

  1. Observe the Freeze Frame/Failure Records for this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

--

Go to Step 4

Go to Testing for Intermittent Conditions and Poor Connections

4

  1. Turn OFF the ignition.
  2. Disconnect the HO2S 1.
  3. Connect a 3-amp fused jumper wire between the high signal circuit of the HO2S 1 harness connector on the engine harness side and a good ground.
  4. Turn ON the ignition, with the engine OFF.
  5. Observe the HO2S 1 parameter with a scan tool.

Is the HO2S 1 parameter less than the specified value?

100 mV

Go to Step 6

Go to Step 5

5

Test the HO2S 1 high signal circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 12

Go to Step 9

6

  1. Remove the jumper wire from the previous step.
  2. Connect a 3-amp fused jumper wire between the high signal circuit of the HO2S 1 harness connector on the engine harness side and the low signal circuit of the HO2S 1 harness connector on the engine harness side.
  3. Observe the HO2S 1 parameter with a scan tool.

Is the HO2S 1 parameter less than the specified value?

100 mV

Go to Step 8

Go to Step 7

7

Test the HO2S 1 low signal circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 12

Go to Step 9

8

Test for shorted terminals and for poor connections at the HO2S 1. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

--

Go to Step 12

Go to Step 10

9

Test for shorted terminals and for poor connections at the powertrain control module (PCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

--

Go to Step 12

Go to Step 11

10

Notice: Refer to Silicon Contamination of Heated Oxygen Sensors Notice in the Preface section.

    Important: The HO2S 1 may be damaged due to contamination.

  1. Prior to replacing the HO2S inspect for the following sources of contamination:
  2. • A silicon contaminated HO2S 1
    • Fuel contamination--Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Engine oil consumption--Refer to Oil Consumption Diagnosis .
    • Engine coolant consumption--Refer to Loss of Coolant .

    Notice: Refer to Heated Oxygen Sensor Resistance Learn Reset Notice in the Preface section.

  3. Replace the HO2S 1. Refer to Heated Oxygen Sensor 1 Replacement .

Did you complete the replacement?

--

Go to Step 12

--

11

Replace the PCM. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

--

Go to Step 12

--

12

  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

--

Go to Step 2

Go to Step 13

13

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List - Vehicle

System OK