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For 1990-2009 cars only
Makes 🢒 Buick 🢒 2003 🢒 LeSabre 🢒 Body and Accessories 🢒 Body Control System 🢒 DTC P0134

Circuit Description

Heated oxygen sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is first started, the powertrain control module (PCM) operates in an Open Loop mode, ignoring the HO2S signal voltage when calculating the air-to-fuel ratio. The PCM supplies the HO2S with a reference or bias voltage of about 450 mV. The HO2S generates a voltage within a range of 0-1,000 mV that fluctuates above and below bias voltage once in Closed Loop. A high HO2S voltage output indicates a rich fuel mixture. A low HO2S voltage output indicates a lean mixture. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature and provide an accurate voltage signal. If the PCM detects that the HO2S 1 voltage remains at or near the bias voltage amount, DTC P0134 will set.

Each HO2S has the following circuits:

    • HO2S 1 high signal
    • HO2S 1 low signal
    • HO2S 1 heater ignition 1 voltage
    • HO2S 1 heater ground

Conditions for Running the DTC
    • DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, 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 parameter is longer than 200 seconds.
    • The system voltage is between 9-18 volts.

Conditions for Setting the DTC

The PCM detects that 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. A normally functioning HO2S 1 voltage signal will fluctuate above and below the bias voltage amount.

    2.

  2. The voltage reading must change from the bias amount to below the specified amount when the signal circuits are jumped to a good ground. This step checks the continuity of the signal circuits.

    3.

  3. This step verifies that there are functional HO2S 1 heater power and ground circuits.

    4.

  4. The conditions listed in the table may contribute to the failure of the HO2S. The conditions listed apply only to this type of failure.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Engine Controls Connector End Views or Powertrain Control Module Connector End Views

1

Did you perform the Diagnostic System Check-Engine Controls?

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Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

  1. Start the engine.
  2. Allow the engine to idle at operating temperature.
  3. Clear the DTC and record the Freeze/Frame Failure Records.
  4. Observe the heated oxygen sensor (HO2S) 1 voltage parameter with a scan tool.

Does the HO2S 1 voltage fluctuate rapidly above and below the specified range?

350-550 mV

Go to Step 3

Go to Step 4

3
  1. Observe the Freeze Frame/Failure Records 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. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

--

Go to Step 4

Go to Intermittent Conditions

4

  1. Turn OFF the ignition.
  2. Disconnect the HO2S 1 connector.
  3. Connect a 3-amp fused jumper wire between the HO2S 1 low signal circuit of the engine harness and a good ground.
  4. Connect a 3-amp fused jumper wire between the HO2S 1 high signal circuit of the engine harness and a good ground.
  5. Turn ON the ignition, with the engine OFF.
  6. Observe the HO2S 1 voltage parameter with a scan tool.

Is the HO2S 1 voltage less than the specified value?

25 mV

Go to Step 6

Go to Step 5

5
  1. Turn OFF the ignition.
  2. Disconnect the powertrain control module (PCM).
  3. Measure the resistance of the HO2S 1 high signal circuit. Refer to Circuit Testing in Wiring Systems.
  4. Measure the resistance of the HO2S 1 low signal circuit. Refer to Circuit Testing in Wiring Systems.

Is the resistance within the specified range?

0-5 ohms

Go to Step 9

Go to Step 10

6

  1. Turn OFF the ignition.
  2. Remove the jumper wires from the HO2S 1 signal circuit terminals.
  3. Connect a test lamp between the heater ignition 1 voltage circuit of the HO2S, and the heater ground circuit of the HO2S, at the engine harness side.
  4. Turn ON the ignition, with the engine OFF.

Does the test lamp illuminate?

--

Go to Step 8

Go to DTC P0135

7

Inspect for the following that may affect the HO2S operation:

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.

    • HO2S contamination

Notice: Do not remove the pigtail from either the heated oxygen sensor (HO2S) or the oxygen sensor (O2S). Removing the pigtail or the connector will affect sensor operation.

Handle the oxygen sensor carefully. Do not drop the HO2S. Keep the in-line electrical connector and the louvered end free of grease, dirt, or other contaminants. Do not use cleaning solvents of any type.

Do not repair the wiring, connector or terminals. Replace the oxygen sensor if the pigtail wiring, connector, or terminal is damaged.

This external clean air reference is obtained by way of the oxygen sensor signal and heater wires. Any attempt to repair the wires, connectors, or terminals could result in the obstruction of the air reference and degraded sensor performance.

The following guidelines should be used when servicing the heated oxygen sensor:

   • Do not apply contact cleaner or other materials to the sensor or vehicle harness connectors. These materials may get into the sensor causing poor performance.
   • Do not damage the sensor pigtail and harness wires in such a way that the wires inside are exposed. This could provide a path for foreign materials to enter the sensor and cause performance problems.
   • Ensure the sensor or vehicle lead wires are not bent sharply or kinked. Sharp bends or kinks could block the reference air path through the lead wire.
   • Do not remove or defeat the oxygen sensor ground wire, where applicable. Vehicles that utilize the ground wired sensor may rely on this ground as the only ground contact to the sensor. Removal of the ground wire will cause poor engine performance.
   • Ensure that the peripheral seal remains intact on the vehicle harness connector in order to prevent damage due to water intrusion. The engine harness may be repaired using Packard's Crimp and Splice Seals Terminal Repair Kit. Under no circumstances should repairs be soldered since this could result in the air reference being obstructed.

    • Chafed, burnt, cut, pinched, or otherwise damaged HO2S wiring
    • The HO2S must have a clean air reference in order to function properly. This clean air reference is obtained by way of the HO2S wires. Obstruction of the air reference and degraded HO2S performance could result from any attempt to repair the above conditions.
    • Exhaust system leaks or restrictions
    • Evaporative emissions (EVAP) system malfunction.
        Inspect the EVAP control system. Refer to Inspection/Maintenance Evaporative Emission System Set .
    • The fuel pressure
        Incorrect fuel pressure can affect HO2S operation. Refer to Fuel System Diagnosis .

Did you find and correct the condition?

--

Go to Step 13

Go to Step 8

8

Test for an intermittent and for a poor connection at the harness connector of the HO2S 1. 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 11

9

Test for an intermittent and for a poor connection at the harness connector of 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

10

Repair the signal circuit that has an open or high resistance. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 13

--

11

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

Did you complete the replacement?

--

Go to Step 13

--

12

Replace the PCM. Refer to Powertrain Control Module Replacement .

Did you complete the replacement?

--

Go to Step 13

--

13
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

--

Go to Step 2

Go to Step 14

14

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List

System OK