GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2002 🢒 Tracker - 2WD 🢒 Engine 🢒 Engine Controls - 2.5L (LE8) 🢒 DTC P0134 or P0154

Circuit Description

The DTC P0134 Heated Oxygen Sensor (HO2S) Circuit Insufficient Activity Bank 1 Sensor 1 diagnostic monitors the HO2S switching time. The DTC P0154 Heated Oxygen Sensor (HO2S) Circuit Insufficient Activity Bank 2 Sensor 1 diagnostic monitors the HO2S switching time. The heated oxygen sensor (HO2S) produces a voltage that varies between 100 mV and 900 mV under normal operating conditions. The powertrain control module (PCM) monitors this voltage and determines if the exhaust is indicating a lean or rich fuel mixture. If the voltage input at the PCM is about 100 mV the fuel mixture is lean, and if the voltage input is about 900 mV the fuel mixture is rich. The PCM constantly monitors the HO2S signal during Closed Loop operation and compensates for a rich or a lean condition by decreasing or increasing the fuel injector pulse width as necessary. If the HO2S 1 voltage remains at or near 450 mV for an extended period of time, DTC P0134 will be set.

Air Fuel Mixture

Exhaust O2 Content

HO2S 1 Output

Fuel System Response

Lean Mixture

High Oxygen

Low Voltage

Rich Command

Rich Mixture

Low Oxygen

High Voltage

Lean Command

Conditions for Running the DTC
    • The barometric pressure (BARO) is more than 75 kPa.
    • The engine coolant temperature (ECT) is between -8°C (+18°F) and +110°C (230°F).
    • The intake air temperature (IAT) is more than -8°C (+18°F) at engine start up.

Conditions for Setting the DTC
    • The HO2S 1 voltage remains less than or equal to 450 mV for 30 seconds.
    • The maximum HO2S 1 voltage remains less than 450 mv.

Action Taken When the DTC Sets
    • The PCM illuminates the malfunction indicator lamp (MIL) after 2 consecutive ignition cycles in which the diagnostic runs with the fault active.
    • The PCM records the operating conditions at the time the diagnostic fails. This information is stored in the Freeze Frame buffer.

Conditions for Clearing the MIL/DTC
    • The MIL turns OFF after three consecutively passing trips without a fault present.
    • A history DTC will clear after 40 consecutive warm-up cycles without a fault.
    • Perform the scan tool Clear DTC Information function in order to clear the DTC.

Diagnostic Aids

Check for any of the following conditions:

    • If any DTCs other than fuel trim P0171, P0172, P0174, P0175, misfire P0300-P0306, exhaust gas recirculation (EGR) P0400, and other HO2S are set, diagnosis those DTCs first.
    • Any vacuum leaks--Check for disconnected or damaged vacuum hoses and for vacuum leaks at the intake manifold, the throttle body, the EGR system, and the crankcase ventilation system.
    • Check for exhaust leaks near the HO2S.
    • The correct fuel pressure--The fuel system can go lean if the fuel pressure is too low, and DTC P0134 or the DTC P0154 may set. Refer to Fuel System Diagnosis .
    • The fuel pressure--The system will go rich or lean if pressure is too high or too low. The PCM can compensate for minor changes. However, if the fuel pressure is too high or too low, a DTC may set.
    • Check the evaporative emissions (EVAP) canister for fuel saturation--If the canister is full of fuel, check the canister control and the hoses.
    • Check for a leaking fuel pressure regulator diaphragm by checking vacuum line to regulator for the presence of fuel.
    • A contaminated HO2S--A contaminated oxygen sensor can fail to enter or remain in Closed Loop. Silicon contamination of the HO2S can cause a lazy HO2S voltage to be indicated. Silicone contamination is indicated by a powdery white deposit on the portion of the HO2S exposed to the exhaust stream. If contamination is found, determine the cause and correct the condition before replacing the HO2S.
    • A poor connection at the PCM--Inspect the harness connectors for backed out terminal, improper mating, broken locks, improperly formed or damaged terminals, and a poor terminal-to-wire connection.
    • A damaged wiring harness--Inspect the wiring harness for damage. If the harness appears to be OK, observe the applicable HO2S display on the scan tool while moving the connectors and the wiring harnesses related to the sensor. A change in the HO2S display will indicate the location of the fault.
    • Follow DTC P0171, DTC P0174, DTC P0172, or DTC P0175 for fuel system checks.

If a DTC P0134 or a DTC P0154 is intermittent, driving the vehicle under the conditions outlined in the Inspection/Maintenance (I/M) section can verify whether the fault is present. Refer to Inspection/Maintenance Heated Oxygen Sensor/Oxygen Sensor System Set .

An intermittent malfunction may be caused by a fault in the HO2S sensor circuit. Inspect the wiring harness and components for an intermittent condition. Refer to Intermittent Conditions .

If the DTC P0134 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.

Test Description

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

  1. The Diagnostic System Check-Engine Controls prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

    2.

  2. This step determines if the fault is present. The vehicle must be at operating temperature.

    3.

  3. This step checks whether the malfunction that caused the DTC P0134 or DTC P0154 is still present. Driving the vehicle under these conditions will verify whether the fault is present. After performing the scan tool clear DTC information function, the DTC P0134 or DTC P0154 diagnostic can be monitored on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If a DTC P0134 or DTC P0154 appears in the Not Ran Since Code Cleared list, the DTC diagnostic has not yet run. When the DTC does not appear in the Not Ran Since Code Cleared list, the DTC diagnostic has run. If the MIL is NOT illuminated, and there is no Pending DTC Status in DTC Information, the DTC diagnostic has passed. The DTCs MUST be cleared in order to view the Current Status of the Not Ran Since Code Cleared list. DO NOT forget that the Not Ran Since Code Cleared list only indicates that the test has run, not whether the test passed or failed. The DTC Information screen must be checked for Current or Pending status in order to determine the outcome of the diagnostic test involved.

    4.

  4. This step checks for a short to voltage on the HO2S signal circuit.

    5.

  5. This step checks for an open in the HO2S ground circuit.

    6.

  6. This step checks the HO2S signal circuit. The DMM is used as a low Current voltage source, taking the place of the HO2S. This test verifies whether the signal wire is good, and whether the PCM is able to receive and process a signal from the HO2S.

    7.

  7. A possible cause of a voltage short to the HO2S signal circuit is water. Check the wiring harness and PCM connectors for water that may cause ignition positive voltage to be shorted to the signal circuit.

    8.

  8. Clearing the DTCs by removing the DOME fuse also clears the PCM long term memory. Using the scan tool to clear DTCs leaves the long term memory active. DTC emitting diagnostics may not run to completion as expected unless the long term memory is cleared. Removal of the DOME fuse also clears the time display of the radio. The DTC P0134 or DTC P0154 diagnostic can be monitored on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If a DTC P0134 or DTC P0154 appears in the Not Ran Since Code Cleared list, the DTC P0134 or DTC P0154 diagnostic has not yet run. When the DTC P0134 or DTC P0154 does not appear in the Not Ran Since Code Cleared list, the DTC P0134 or DTC P0154 diagnostic has run. If the MIL is NOT illuminated, and there is no Pending DTC Status in DTC Information, the DTC P0134 or DTC P0154 diagnostic has passed. The DTCs MUST be cleared in order to view the Current Status of the Not Ran Since Code Cleared list. DO NOT forget that the Not Ran Since Code Cleared list only indicates that the test has run, not whether the test passed or failed. The DTC Information screen must be checked for Current or Pending status, in order to determine the outcome of the diagnostic test involved.

Step

Action

Value(s)

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

Are any DTCs set other than fuel trim and HO2S DTCs?

--

Go to Diagnostic Trouble Code (DTC) List

Go to Step 3

3

  1. Start the engine.
  2. Run the engine until the engine reaches a normal operating temperature.
  3. Increase the engine speed to 2,000 RPM for 1 minute.
  4. Operate the vehicle within the parameters specified in the first 3 items listed under Conditions for Setting the DTC.
  5. Monitor the HO2S 1 voltage with a scan tool.

Does the HO2S voltage switch below and above the specified value?

300-600 mV

Go to Step 4

Go to Step 5

4

  1. Turn ON the ignition, leaving the engine OFF.
  2. Perform the scan tool clear DTC information function.
  3. Operate the vehicle within Freeze Frame conditions as specified or until the P0134 diagnostic test has run. Refer to the Test Description.

Does the HO2S voltage switch below and above the specified value?

300-600 mV

Go to Diagnostic Aids

Go to Step 5

5

  1. Turn OFF the ignition,
  2. Disconnect the electrical connector of the suspect HO2S.
  3. Disconnect the C2 electrical connector of the PCM.
  4. Turn ON the ignition, leaving the engine OFF.
  5. Connect a DMM from ground to the oxygen sensor signal circuit on the harness side of the electrical connector.

Is the voltage at the specified value?

0.0 V

Go to Step 6

Go to Step 10

6

  1. Turn OFF the ignition.
  2. Connect the PCM C2 electrical connector.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the HO2S ground circuit at the HO2S connector with a test lamp connected to B+.

Does the test lamp illuminate?

--

Go to Step 7

Go to Step 8

7

  1. Use the J 39200 DMM and select the MilliVolt DC scale.
  2. Connect one lead of the DMM to B+.
  3. Connect the other lead of the DMM to the HO2S signal circuit.
  4. Start the engine.
  5. Observe the HO2S voltage parameter on the scan tool.

Does the scan tool indicate a HO2S voltage at the specified value?

1,000 mV

Go to Step 11

Go to Step 9

8
  1. Check for an open in the HO2S ground circuit.
  2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 13

Go to Step 12

9
  1. Check the HO2S signal circuit for the following conditions:
    2. • Open Circuit
    • Short to ground
    • High circuit resistance
  2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 13

Go to Step 12

10

Repair the short to voltage in the HO2S signal circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 13

--

11

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

Did you complete the replacement?

--

Go to Step 13

--

12

Important: The replacement PCM must be programmed.

Replace the PCM. Refer to Powertrain Control Module Replacement .

Did you complete the replacement?

--

Go to Step 13

--

13

  1. Turn OFF the ignition.
  2. Remove the DOME fuse for 30 seconds.
  3. Install the DOME fuse.
  4. Reset the radio clock time. Refer to Radio/Audio System Description and Operation in Entertainment.
  5. Start the engine.
  6. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text or until the DTC P0134 or DTC P0154 diagnostic test has run.

Does the DTC run and pass?

--

Go to Step 14

Go to Step 2

14

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