GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2002 🢒 DeVille 🢒 DTC 🢒 DTC P1134 or P1154

Circuit Description

The heated oxygen sensor (HO2S) is a sensor used in order to detect the 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 activity in order to determine a time ratio for the lean to rich and rich to lean switches. A lean to rich switch occurs when the HO2S signal voltage changes from less than 300 mV to more than 600 mV. A rich to lean switch occurs when the HO2S signal voltage switches from more than 600 mV to less than 300 mV. The PCM counts the number of lean to rich and rich to lean switches for 100 seconds. The PCM records the amount of time required to complete all transitions. With this information, the PCM determines an average transition time for the lean to rich switches, and the rich to lean switches. By dividing the rich to lean time by the lean to rich time, the PCM determines the average transition time ratio. This DTC indicates that the PCM detects an average transition time ratio that is out of range.

Conditions for Running the DTC
    • DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0125, P0131, P0132, P0135, P0151, P0152, P0155, P0201-P0208, P0300, P0410, P0440, P0442, P0443, P0446, P0449, P1415, P1416, or P1441 are not set.
    • The engine speed is between 1,200-2,800 RPM.
    • The mass air flow (MAF) is between 15-35 g/s.
    • The throttle position (TP) angle is more than 3 percent.
    • The exhaust gas recirculation (EGR) flow test is not active.
    • The secondary air injection (AIR) system tests are not active.
    • The catalyst test is not active.
    • The system voltage is between 9-18  volts.
    • The coolant temperature is more than 75°C (166°F).
    • The transmission is not in Park, Reverse, or Neutral.
    • The Closed Loop fuel control is enabled.
    • The above conditions are met for 3 seconds.

Conditions for Setting the DTC
    • The ratio of average transition times is not between 0.50 and 3.9.
    • The O2 voltage is between 325-625 mV.

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 DTC
    • 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 non-emission related diagnostic.
    • Clear 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.

If the condition is intermittent, refer to Intermittent Conditions .

Test Description

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

  1. This step tests if other possible causes of this DTC have already been diagnosed.

    2.

  2. Diagnose other DTCs first because they may be the cause of this DTC setting.

    3.

  3. With the engine running warm and at fast idle, and with the coolant temperature at least 85°C (185°F), the oxygen sensor voltage should rapidly swing above 0.60 volt and below 0.30 volt.

    4.

  4. This step tests if the oxygen sensor voltage is swinging between rich and lean very slowly, or not at all.

    5.

  5. This step tests for causes of oxygen sensor failure. If the sensor is replaced without finding the cause of contamination, premature failure of the new sensor may result.

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

Were you sent here from another DTC?

--

Go to Step 4

Go to Step 3

3

Are any other DTCs set?

--

Go to Diagnostic Trouble Code (DTC) List

Go to Step 4

4

  1. Start the engine.
  2. Operate the vehicle until the engine reaches normal operating temperature.
  3. View both the engine speed and the affected HO2S display on the scan tool.
  4. Operate engine at 2,000 RPM for two minutes.

Does the affected HO2S voltage rapidly swing above and below the range specified?

325-625 mV

Go to Step 5

Go to Step 6

5

With engine running at 2,000 RPM, observe the scan tool display Loop Status.

Does the display indicate Closed?

--

Go to Intermittent Conditions

Go to Step 9

6

Does the HO2S voltage remain between the specified values longer than it swings outside this range?

325-625 mV

Go to Step 9

Go to Step 7

7
  1. Test for poor connections at the PCM. 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
  1. Test for poor connections at the HO2S. 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 9

9

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.

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

  1. Inspect and test for the following conditions:
    2. • High resistance in the HO2S high or low signal circuits
    • Incorrect or contaminated fuel--Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • An incorrect RTV gasket sealer
    • An over-rich operation
  2. 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

--

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