GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2003 🢒 Grand Prix 🢒 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 to 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 1 has the following circuits:

    • HO2S 1 high signal
    • HO2S 1 low reference
    • HO2S 1 heater ignition voltage
    • HO2S 1 heater low control
    • Low reference loop

Conditions for Running the DTC
    • DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0410, P0440, P0442, P0443, P0446, P0449, P1441 are not set.
    •  The Engine Run Time parameter is at least 4 minutes.
    • The system voltage is between 9-18 volts.

Conditions for Setting the DTC

The PCM detects that the HO2S 1 signal voltage remains between 382-525 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. A voltage reading other than the specified amount in this step indicates an open circuit condition in the high signal circuit or the PCM.

    3.

  3. This step inspects the HO2S 1 signal circuits from the HO2S connector and the PCM connectors, including the low reference loop between the PCM connectors.

    4.

  4. This step inspects for correct HO2S 1 heater circuit operation up to the HO2S connector. The heater low control is controlled by the PCM. The engine must be running to enable the HO2S heater.

  5. 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?

--

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. Turn ON the ignition, with the engine OFF.
  4. Measure the voltage from the high signal circuit of the HO2S 1 harness connector on the engine harness side to a good ground with a DMM .

Is the HO2S 1 voltage within the specified range?

0.425-0.500 V

Go to Step 5

Go to Step 6

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

Is the HO2S 1 voltage less than the specified value?

25 mV

Go to Step 8

Go to Step 6

6

  1. Turn OFF the ignition.
  2. Disconnect both powertrain control module (PCM) connectors.
  3. Measure the resistance of each of the following circuits with a DMM:
    4. • HO2S 1 high signal circuit between HO2S connector and the PCM connector
    • HO2S 1 low reference circuit between HO2S connector and the PCM connector
    • Low reference loop between pin C1-29 and pin C2- 80 of the PCM connectors--Refer to Circuit Testing in Wiring Systems.

Is the resistance of each circuit less than the specified value?

5 ohms

Go to Step 11

Go to Step 7

7

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

Did you complete the repair?

--

Go to Step 14

--

8

  1. Remove the jumpers from the HO2S 1 terminals.
  2. Connect a test lamp between the HO2S heater ignition voltage circuit and heater low control circuit terminals on the engine harness side.
  3. Start the engine.

Does the test lamp illuminate?

--

Go to Step 9

Go to DTC P0135

9

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 for contamination

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

    • 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 14

Go to Step 10

10

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 14

Go to Step 12

11

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 14

Go to Step 13

12

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

Did you complete the replacement?

--

Go to Step 14

--

13

Replace the PCM. Refer to Powertrain Control Module Replacement .

Did you complete the replacement?

--

Go to Step 14

--

14
  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 15

15

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