GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The powertrain control module (PCM) continuously monitors the heated oxygen sensor (HO2S 1) activity for 100 seconds. During the monitor period, the PCM counts the number of times that the HO2S 1 switches from rich to lean and from lean to rich and adds the amount of time that the HO2S 1 took in order to complete all of the switches. With this information, you can determine an average time for all of the switches. If the average time to switch is too slow, a DTC P0133 will set.

Do not attempt to repair the HO2S. Replace the entire HO2S if the following conditions exist:

    • Damaged wiring
    • Damaged electrical connector
    • Damaged terminals

Conditions For Running The DTC

    • DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0201, P0202, P0203, P0204, P0205, P0206, P0300, P0336, P0440, P0446, P0452, P0453, P0507, P0601, P0602, P0604, P0606, P1120, P1220, P1221, P1271, P1275, P1280, P1484, P1512, P1514, P1515, P1516, P1621, P1635, P1639, P1680, or P1681 are not set.
    • The fuel level sensor is more than 10 percent.
    • The engine coolant temperature (ECT) sensor is more than 70°C (158°F).
    • The engine speed is between 1,450-1,900 RPM.
    • The loop status is closed.
    • The throttle position (TP) indicated angle is between 25-30 percent.
    • The evaporative emission (EVAP) purge solenoid command is more than 10 percent.
    • The above conditions have been met for 30 seconds.

Conditions For Setting The DTC

The average HO2S 1 response times are more than 850 mS for rich to lean sweeps or 950 mS for lean to rich sweeps or the sum of rich to lean and lean to rich sweeps is more than 2100 mS.

Action Taken When the DTC Sets

    • The malfunction indicator lamp (MIL) will illuminate after two consecutive ignition cycles in which the diagnostic runs with the malfunction present.
    • The PCM will record the operating conditions at the time that the diagnostic fails. This information will store in the Freeze Frame/Failure Records buffers.
    • A history DTC stores.

Conditions for Clearing the MIL/DTC

    • The MIL will turn OFF after three consecutive ignition cycles in which the diagnostic runs without a fault.
    • A history DTC will clear after 40 consecutive warm up cycles without a fault.
    • Use a scan tool to clear the DTCs.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. When the system is operating correctly, the HO2S voltage should toggle above and below the specified values.

  2. The specified value is what is measured on a correctly operating system.

  3. The specified value is what is measured on a correctly operating system.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Engine Controls Connector End Views

1

Did you perform the Diagnostic System Check-Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

Important: If any other DTCs are set, except HO2S DTCs, refer to other DTCs first before proceeding with this table.

  1. The engine has reached operating temperature.
  2. Operate the engine above 1,200 RPM for two minutes.
  3. With a scan tool, observe the HO2S voltage parameter.

Does scan tool indicate HO2S voltage varying outside the specified values?

400-500 mV

Go to Step 3

Go to Step 4

3

  1. Observe the Freeze Frame/Failure Records data 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 as specified in the supporting text or as close to the Freeze Frame/Failure Records data that you observed.

Does the DTC fail this ignition?

--

Go to Step 4

Go to Symptoms - Engine Controls

4

Inspect and test for the following conditions:

    • Exhaust leak--Refer to Exhaust Leakage in Engine Exhaust.
    • The HO2S is installed correctly.
    • Damaged wiring--Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 13

Go to Step 5

5

  1. Turn OFF the ignition.
  2. Disconnect the HO2S.
  3. Turn ON the ignition.
  4. Measure the voltage on the HO2S high signal circuit (PCM side) .

Does the voltage measure near the specified value?

450 mV

Go to Step 6

Go to Step 8

6

  1. Jumper the HO2S high signal circuit to the HO2S low signal circuit (PCM side).
  2. With a scan tool, observe HO2S voltage parameter.

Does the scan tool indicate HO2S voltage at or near the specified value?

0 mV

Go to Step 9

Go to Step 7

7

Test the HO2S low signal circuit for an open, high resistance, or short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 13

Go to Step 11

8

Test the HO2S high signal circuit for an open, high resistance, or short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 13

Go to Step 11

9

Test for poor connections at the HO2S. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 13

Go to Step 10

10

Important: Determine the cause of contamination before replacing the sensor.

Inspect and test for the following conditions:

    • Fuel contamination--Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Engine oil or coolant consumption--Refer to Oil Consumption Diagnosis in Engine Mechanical.

Notice: Contamination of the oxygen sensor can result from the use of an inappropriate RTV sealant (not oxygen sensor safe) or excessive engine coolant or oil consumption. Remove the HO2S and visually inspect the portion of the sensor exposed to the exhaust stream in order to check for contamination. If contaminated, the portion of the sensor exposed to the exhaust stream will have a white powdery coating. Silicon contamination causes a high but false HO2S signal voltage (rich exhaust indication). The control module will then reduce the amount of fuel delivered to the engine, causing a severe driveability problem. Eliminate the source of contamination before replacing the oxygen sensor.

    • Use of improper RTV sealant

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

Did you complete the replacement?

--

Go to Step 13

--

11

Test for poor connections at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 13

Go to Step 12

12

Replace the PCM. Refer to Powertrain Control Module Replacement .

Did you complete the replacement?

--

Go to Step 13

--

13

  1. Use the scan tool in order to clear the DTCs.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

--

Go to Step 14

Go to Step 2

14

With a scan tool, observe the stored information, Capture Info.

Does the scan tool display any DTCs that you have not diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List

System OK