GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2001 🢒 Catera 🢒 Engine 🢒 Engine Controls - 3.0L (L81) 🢒 DTC P0134 or P0154

Circuit Description

The wide band heated oxygen sensor (HO2S) measures the amount of oxygen in the exhaust stream more quickly and accurately than the switching style HO2S. The wide range HO2S sensor functions more like an air fuel sensor. The wide band sensor consists of an oxygen sensing cell, an oxygen pumping cell, and a heater. The exhaust gas sample passes through a diffusion gap between the sensing cell and the pumping cell. The engine control module (ECM) supplies a signal voltage to the HO2S and uses this voltage as a reference to the amount of oxygen in the exhaust system. An electronic circuit within the ECM controls the pump current through the oxygen pumping cell in order to maintain a constant signal voltage. The ECM monitors the voltage variation on the signal circuit and attempts to keep the voltage constant by increasing or decreasing the amount of current flow or reversing the direction of the current flow to the pumping cell. By measuring the direction and amount of current required to maintain the signal voltage, the ECM can determine the concentration of oxygen in the exhaust. The signal voltage is displayed as a lambda value. A lambda value of 1 is equal to a stoichiometric air fuel ratio of 14.7:1. Under normal operating conditions, the lambda value will remain around 1. When the system is lean, the oxygen level will be high and the lambda signal will be high or more than 1. When the oxygen level is low, the lambda signal will be low or less than 1. The ECM uses this information to maintain the proper air/fuel ratio.

Conditions for Running the DTC
    • DTCs P0130 or P0150 are not set.
    • The engine is at the operating temperature.
    • The engine has been running for more than 25 seconds.
    • The engine speed must be between 1,400-2,400 RPM.
    • The engine load is 8-12 percent.
    • The mass air flow (MAF) is 18-22 g/s.
    • The throttle position (TP) is 6-10 percent.

Conditions for Setting the DTC

The difference in the air/fuel signal within 10 ms is more than expected.

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

Use the J 35616 Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a component harness connector.

Check for the following conditions:

    • Fuel pressure--If the fuel pressure is too low, this DTC may be set. Refer to Fuel System Diagnosis .
    • Lean injectors
    • Contaminated fuel--Water, in small amounts, can be delivered to the fuel injectors. When this occurs, a lean exhaust will be indicated. Excessive alcohol in the fuel can also cause this condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis for the proper method of checking for fuel contamination.

Test Description

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

  1. Any exhaust leak, even a small one, can affect the operation of the HO2S. The ECM compares the reading of sensor 1 with the reading from sensor 2 as part of the diagnosis. A leak between sensor 1 and sensor 2 may set a DTC.

    2.

  2. A short between the signal circuit and the reference ground circuit or the pump current input and output circuits may not appear on the voltage tests. The ECM must be disconnected and each circuit tested for continuity with the other HO2S circuits.

P0134 or P0154 Heated Oxygen Sensor (HO2S) Circuit Insufficient Activity Sensor 1

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

1

Did you perform the Diagnostic System Check-Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

  1. Using the scan tool, store the DTC information from the ECM into the scan tool.
  2. Clear the DTC information from the ECM.
  3. Turn OFF the ignition for 15 seconds.
  4. Start and idle the engine until normal operating temperature is reached.
  5. Operate the vehicle within the Conditions For Running the DTC, or as close to the data observed in the Freeze Frame/Failure Records.
  6. Using the scan tool, check for any DTCs.

Did the DTC fail this ignition?

--

Go to Step 3

Go to Diagnostic Aids

3

  1. Inspect the exhaust system for any leaks upstream from the affected oxygen sensor including the AIR distribution system.
  2. Inspect for any exhaust leaks between sensor 1 and sensor 2.
  3. Repair the exhaust leak as necessary.

Did you find and correct the condition?

--

Go to Step 16

Go to Step 4

4
  1. Turn OFF the ignition.
  2. Visually/physically inspect the following items:
    3. • Ensure that the HO2S is securely installed.
    • Check for terminal corrosion or water intrusion.
    • Check the terminal tension at the HO2S connectors.
    • Check for damaged wiring.
  3. Repair as necessary. Refer to Wiring Repairs and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 16

Go to Step 5

5
  1. Turn OFF the ignition.
  2. Disconnect the connector for the HO2S that applies to this DTC.
  3. Turn ON the ignition, with the engine OFF.
  4. Measure the voltage of the HO2S signal circuit at the ECM side of the connector to battery ground.

Is the voltage within the specified range?

2-4 V

Go to Step 6

Go to Step 10

6

Measure the voltage of the reference ground circuit at the ECM side of the connector to battery ground.

Is the voltage within the specified range?

2-4 V

Go to Step 7

Go to Step 10

7

Measure the voltage of the pump current input circuit at the ECM side of the connector to battery ground.

Is the voltage within the specified range?

0.2-0.4 V

Go to Step 8

Go to Step 10

8

Measure the voltage of the pump current output circuit at the ECM side of the connector to battery ground.

Is the voltage within the specified range?

0.2-0.4 V

Go to Step 9

Go to Step 10

9

  1. Turn OFF the ignition.
  2. Disconnect the ECM.
  3. Test each of the circuits on the affected HO2S for a short to each other.
  4. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 16

Go to Step 13

10

Is the voltage more than the specified value?

0.4 V

Go to Step 12

Go to Step 11

11
  1. Test the affected circuit for the following conditions:
    2. • Open
    • Short to ground
    • High resistance
  2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 16

Go to Step 14

12
  1. Test the affected circuit for a short to voltage.
  2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 16

Go to Step 14

13

Replace the HO2S. Refer to Heated Oxygen Sensor Replacement .

Did you complete the replacement?

--

Go to Step 16

--

14
  1. Check for a poor connection or poor terminal tension at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
  2. Repair as necessary. Refer to Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 16

Go to Step 15

15

Important: 

   • Perform the idle learn procedure when replacing the ECM.
   • This vehicle is equipped with a theft deterrent system that interfaces with the ECM. Program the new ECM with the frequency code of the theft deterrent module that is currently on the vehicle.

Replace the ECM. Refer to Engine Control Module Replacement .

Did you complete the action?

--

Go to Step 16

--

16
  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 17

Go to Step 2

17

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