GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2001 🢒 Seville - RHD 🢒 DTC 🢒 DTC P0134 or P0154

Circuit Description

The heated oxygen sensor (HO2S) is a sensor used to detect oxygen-content in the exhaust. The powertrain control module (PCM) supplies the sensor with a signal circuit and a ground circuit. The PCM supplies a bias voltage between the circuits. The sensor varies the voltage based on the oxygen content in the exhaust. When the exhaust stream is lean (more oxygen), the sensor produces a low voltage signal. When the exhaust stream is rich (less oxygen), the sensor produces a high voltage signal.

The PCM monitors the HO2S signal during closed loop. In order to correct for rich or lean conditions, the PCM adjusts the injector pulse width. This DTC indicates that the HO2S voltage remained at or near the bias voltage for a calibrated period of time.

Conditions for Running the DTC
    • DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0201-P0208, P0410, P0440, P0442, P0443, P0446, P0449, P1133, P1415, P1416, or P1441 are not set.
    • The system voltage is between 9-18 volts.
    • The engine is running for 3 minutes.
    • The exhaust gas recirculation (EGR) flow diagnostic test is not active.
    • The catalyst diagnostic test is not active.
    • The secondary air injection (AIR) diagnostic test is not active.

Conditions for Setting the DTC

HO2S signal voltage remain within 400-500 mV for approximately 1 minute.

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

Notice: Do not solder heated oxygen sensor wires. Soldering the wires will result in the loss of the air reference to the sensor. Refer to Engine Electrical for proper wire and connection repair techniques.

For intermittent conditions, refer to Intermittent Conditions .

Test Description

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

  1. With the harness connector terminals jumpered together, the scan tool should display an HO2S voltage below 75 mV.

Step

Action

Value(s)

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

Are any DTCs set other than DTC P0134?

--

Go to Diagnostic Trouble Code (DTC) List

Go to Step 3

3
  1. With the engine at operating temperature, raise and hold the engine speed above 1,200 RPM for 2 minutes.
  2. Observe the HO2S voltage display on the scan tool.

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

400-500 mV

Go to Step 4

Go to Step 5

4
  1. Review and record scan tool Failure Records data.
  2. Operate the vehicle within the Failure Records conditions.
  3. With the scan tool, observe the Specific DTC Information for this DTC until the test runs.

Does the scan tool indicate this DTC passed?

--

Go to Intermittent Conditions

Go to Step 5

5

  1. Disconnect the affected HO2S harness connector.
  2. Turn ON the ignition, with the engine OFF.
  3. Jumper the HO2S signal and low circuits in the harness connector (PCM side).
  4. Observe the HO2S voltage display on the scan tool.

Does the scan tool indicate an HO2S voltage below the specified value?

75 mV

Go to Step 7

Go to Step 6

6
  1. Turn OFF the ignition.
  2. Disconnect the PCM connector C1. Refer to Powertrain Control Module Replacement .
  3. Test for the following conditions:
    4. • Open signal circuit
    • Open low circuit
    • Poor terminal connections at the PCM
  4. If a condition is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 10

Go to Step 9

7
  1. Inspect for poor terminal connections at the HO2S harness connector. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
  2. If a condition is found, repair as necessary. Refer to Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 10

Go to Step 8

8

Replace the affected HO2S. Refer to Heated Oxygen Sensor Replacement - Bank 1 Sensor 1 or Heated Oxygen Sensor Replacement - Bank 2 Sensor 1 .

Did you complete the replacement?

--

Go to Step 10

--

9

Replace the PCM. Refer to Powertrain Control Module Replacement .

Did you complete the replacement?

--

Go to Step 10

--

10
  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 11

Go to Step 2

11

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