GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2001 🢒 Grand Prix 🢒 Engine 🢒 Engine Controls - 3.8L 🢒 DTC P0134

Circuit Description

The powertrain control module (PCM) supplies a bias voltage of about 450 mV between the heated oxygen sensor (HO2S) high signal and the low signal circuits. When measured with a 10 megaohm DMM, this voltage may display as low as 320 mV. The oxygen sensor varies the voltage within a range of about 1,000 mV when the exhaust is rich, down through about 10 mV when exhaust is lean. The PCM constantly monitors the HO2S signal during Closed Loop operation, and compensates for a rich or lean condition by decreasing or increasing the injector pulse width as necessary. If the HO2S 1 voltage remains at or near the 450 mV bias for an extended time, DTC P0134 will set.

Conditions for Running the DTC
    • DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, 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 engine run time is longer than 200 seconds.

Conditions for Setting the DTC

The HO2S 1 signal voltage remains between 400-500 mV for more than 30 seconds.

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 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.

  2. If the HO2S low signal circuit is shorted to ground, the HO2S voltage will be less than 400 mV when the HO2S high signal circuit is jumped to ground.

    3.

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

    4.

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

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

1

Did you perform the Diagnostic System Check--Engine Control?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

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

  1. Ensure that the engine is at the operating temperature.
  2. Operate the engine above 1,200 RPM for 2 minutes.
  3. With a scan tool, observe the HO2S voltage parameter.

Does scan tool indicate that the HO2S voltage varies outside the specified values?

400-500 mV

Go to Step 3

Go to Step 4

3

Operate the vehicle within the Failure Records conditions.

Does the scan tool indicate this DTC failed this ignition?

--

Go to Step 4

Go to Intermittent Conditions

4

Inspect and test for the following conditions:

    • An exhaust leak--Refer to Exhaust Leakage in Engine Exhaust.
    • Correct HO2S installation
    • Damaged wiring--Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 15

Go to Step 5

5

  1. Turn ON the ignition.
  2. Disconnect the HO2S.
  3. Jumper the HO2S high signal circuit on the PCM side to a good ground.
  4. With a scan tool, observe the HO2S voltage parameter.

Does the scan tool indicate that the HO2S voltage is more than the specified value?

400 mV

Go to Step 6

Go to Step 10

6

  1. Remove the jumper wire.
  2. Measure the voltage on the HO2S high signal circuit on the PCM side, using a DMM that is connected to a good ground.

Does the voltage measure near the specified value?

4.5 V

Go to Step 7

Go to Step 9

7

Measure the voltage on the HO2S low signal circuit on the PCM side, using a DMM that is connected to a good ground.

Does the voltage measure near the specified value?

5 V

Go to Step 11

Go to Step 8

8

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

Did you find and correct the condition?

--

Go to Step 15

Go to Step 13

9

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

Did you find and correct the condition?

--

Go to Step 15

Go to Step 13

10

Test the HO2S low signal circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 15

Go to Step 14

11

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 15

Go to Step 12

12

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-3.8L.
    • Use of an improper RTV sealant--Refer to

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.

in Cautions and Notices.

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

Did you complete the replacement?

--

Go to Step 15

--

13

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 15

Go to Step 14

14

Replace the PCM. Refer to Powertrain Control Module Replacement .

Did you complete the replacement?

--

Go to Step 15

--

15
  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 16

Go to Step 2

16

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