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For 1990-2009 cars only
Makes 🢒 Buick 🢒 2006 🢒 Rendezvous - FWD 🢒 Accessories 🢒 Navigation Systems 🢒 DTC P0134

Circuit Description

Heated oxygen sensors (HO2S) are used for fuel control and catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is started, the control module operates in an Open Loop mode, ignoring the HO2S signal voltage while calculating the air-to-fuel ratio. The control module supplies the HO2S with a reference, or bias, voltage of approximately 450 mV. While the engine runs, the HO2S heats up and begins to generate a voltage within a range of 0-1,000 mV. This voltage will fluctuate above and below the bias voltage. Once sufficient HO2S voltage fluctuation is observed by the control module, Closed Loop is entered. The control module uses the HO2S voltage to determine the air-to-fuel ratio. An HO2S voltage that increases above bias voltage toward 1,000 mV indicates a rich fuel mixture. An HO2S voltage that decreases below bias voltage toward 0 mV indicates a lean fuel mixture.

The heating elements within each HO2S heat the sensor. The powertrain control module (PCM) controls the HO2S heater control circuit. The HO2S heater diagnostic monitors the current draw through the HO2S output driver module (ODM) when the engine is running. This allows the system to enter Closed Loop earlier and the control module to calculate the air-to-fuel ratio sooner.

If the PCM detects that the HO2S 1 voltage remains at or near the bias voltage amount, DTC P0134 will set.

The HO2S 1 has the following circuits:

    • A HO2S 1 high signal circuit
    • A HO2S 1 low reference circuit
    • A HO2S 1 heater ignition voltage circuit
    • A HO2S 1 heater low control circuit

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0134 HO2S Insufficient Activity Bank 1 Sensor 1

Conditions for Running the DTC
    • DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0125, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0220, P0442, P0443, P0446, P0449, P0451, P0452, P0453, P0454, P0455, P0464, P0496, P2135 are not set.
    • DTCs P2A01, P0401, and P0420 are not commanding fuel.
    • The system voltage is between 9-18 volts.
    • The scan tool special functions are not active.
    • The HO2S 1 Heater parameter is ON.
    • The Engine Run Time parameter is more than 2 minutes.

Conditions for Setting the DTC
    • The PCM detects that the HO2S 1 signal voltage is between 382-525 mV for more than 30 seconds.
    • This diagnostic runs continuously.

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.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

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

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2
  1. Start the engine.
  2. Allow the engine to idle at operating temperature. Refer to Scan Tool Data List .
  3. Clear the DTC and record the Freeze Frame/Failure Records.
  4. Observe the affected HO2S parameter with a scan tool.

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

381-525 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 Testing for Intermittent Conditions and Poor Connections

4
  1. Turn OFF the ignition.
  2. Disconnect the affected heated oxygen sensor (HO2S) 1.
  3. Turn ON the ignition, with the engine OFF.
  4. Observe the affected HO2S parameter on a scan tool.

Is the voltage more than the specified value?

475 mV

Go to Step 10

Go to Step 5

5

Measure the voltage between the HO2S 1 low signal circuit, on the engine harness side, and a good ground with a DMM. Refer to Circuit Testing .

Is the voltage more than the specified value?

1 V

Go to Step 11

Go to Step 6

6
  1. Connect a 3-amp fused jumper wire between the HO2S 1 high signal circuit, on the engine harness side, and a good ground.
  2. Observe the HO2S parameter with a scan tool.

Is the voltage less than the specified value?

15 mV

Go to Step 7

Go to Step 12

7
  1. Remove the jumper wire from the previous step.
  2. Connect a 3-amp fused jumper wire between the high signal circuit and the low signal circuit of the HO2S 1 on the engine harness side.
  3. Observe the HO2S parameter with a scan tool.

Is the voltage less than the specified value?

15 mV

Go to Step 8

Go to Step 13

8
  1. Turn OFF the ignition.
  2. Measure the resistance between the low signal circuit and heater low control circuit on the engine harness side of the HO2S 1. Refer to Circuit Testing .

Is the resistance less than the specified value?

200 K ohms

Go to Step 14

Go to Step 9

9

Probe the HO2S 1 low signal circuit with a test lamp that is connected to B+. Refer to Probing Electrical Connectors .

Does the test lamp illuminate?

--

Go to Step 15

Go to Step 16

10

Test the HO2S 1 high signal circuit for a short to voltage. Refer to Circuit Testing , Wiring Repairs , and Heated Oxygen Sensor Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 21

Go to Step 18

11

Test the HO2S 1 low signal circuit for a short to voltage. Refer to Circuit Testing , Wiring Repairs , and Heated Oxygen Sensor Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 21

Go to Step 18

12

Test the HO2S 1 high signal circuit for an open or high resistance. Refer to Circuit Testing , Wiring Repairs , and Heated Oxygen Sensor Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 21

Go to Step 18

13

Test the HO2S 1 low signal circuit for an open or high resistance. Refer to Circuit Testing , Wiring Repairs , and Heated Oxygen Sensor Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 21

Go to Step 18

14

Test the HO2S 1 low signal circuit for a short to the HO2S 1 heater low control circuit. Refer to Circuit Testing , Wiring Repairs , and Heated Oxygen Sensor Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 21

Go to Step 18

15

Test the HO2S 1 low signal circuit for a short to ground. Refer to Circuit Testing , Wiring Repairs , and Heated Oxygen Sensor Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 21

Go to Step 18

16

Inspect for the following that may affect the HO2S operation:

Notice: Refer to Silicon Contamination of Heated Oxygen Sensors Notice in the Preface section.

    • HO2S contamination
    • Engine oil consumption--Refer to Oil Consumption Diagnosis .
    • Engine coolant consumption--Refer to Loss of Coolant .

Notice: Refer to Heated Oxygen and Oxygen Sensor Notice in the Preface section.

    • Chafed, burnt, cut, pinched, or otherwise damaged HO2S wiring
    • Exhaust system leaks or restrictions
    • Evaporative emission (EVAP) system malfunction--Inspect the EVAP control system. Refer to Inspection/Maintenance (I/M) System Check .
    • Incorrect fuel pressure--Refer to Fuel System Diagnosis .

Did you find and correct the condition?

--

Go to Step 21

Go to Step 17

17

Test for shorted terminals and poor connections at the HO2S 1. Refer to Testing for Intermittent Conditions and Poor Connections , Connector Repairs , and Heated Oxygen Sensor Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 21

Go to Step 19

18

Test for shorted terminals and poor connections at the powertrain control module (PCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

--

Go to Step 21

Go to Step 20

19

Notice: Refer to Heated Oxygen Sensor Resistance Learn Reset Notice in the Preface section.

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

Did you complete the replacement?

--

Go to Step 21

--

20

Replace the PCM. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

--

Go to Step 21

--

21
  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 22

22

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List - Vehicle

System OK