GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2004 🢒 Grand Prix 🢒 Engine 🢒 Engine Controls - 3.8L (L26 and L32) 🢒 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 the sensor reaches operating temperature. 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, DTC P0134 will set.

Each HO2S 1 has the following circuits:

    • An HO2S 1 high signal circuit
    • An HO2S 1 low signal circuit
    • An HO2S 1 heater ignition voltage 1 circuit
    • An HO2S 1 heater low control circuit

Conditions for Running the DTC
    • DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0120, P0201, P0202, P0203, P0204, P0205, P0206, P0220, P0442, P0443, P0446, P0449, P0455, P0496, P1106, P1107, P1111, P1112, P1114, P1115, P2135 are not set.
    • The Engine Run Time parameter is more than 2 minutes.
    • DTCs P0136, P0401, and P0420 passed.
    • The system voltage is between 9-18 volts.

Conditions for Setting the DTC

The PCM detects that the HO2S 1 signal voltage remains between 381-525 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.

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. Refer to Scan Tool Data List .
  3. Clear the DTC and record the Freeze/Frame Failure Records.
  4. Observe the HO2S 1 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 Intermittent Conditions

4
  1. Turn OFF the ignition.
  2. Disconnect the heated oxygen sensor (HO2S) 1.
  3. Turn ON the ignition, with the engine OFF.
  4. Observe the HO2S 1 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 heated oxygen sensor (HO2S) 1 low signal circuit, on the engine harness side, and a good ground with a DMM. Refer to Circuit Testing in Wiring Systems.

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 1 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 1 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 of the HO2S 1. Refer to Circuit Testing in Wiring Systems.

Is the resistance less than the specified value?

5 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 in Wiring Systems.

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 in Wiring Systems.

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 in Wiring Systems.

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 in Wiring Systems.

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 in Wiring Systems.

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 in Wiring Systems.

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 in Wiring Systems.

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: 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
    • 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--Refer to Fuel System Diagnosis .

Did you find and correct the condition?

--

Go to Step 21

Go to Step 17

17

Test for an intermittent and for a poor connection at the HO2S 1. Refer to Testing for Intermittent Conditions and Poor Connections , Connector Repairs , and Heated Oxygen Sensor Wiring Repairs in Wiring Systems.

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 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 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 Powertrain Control Module Replacement .

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

System OK