GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2008 🢒 Enclave - AWD 🢒 DTC 🢒 DTC P0133, P0134, P0140, P1133, P2A00, or P2A01

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provide an overview of each diagnostic category.

DTC Descriptors

DTC P0133: HO2S Slow Response Bank 1 Sensor 1

DTC P0134: HO2S Circuit Insufficient Activity Bank 1 Sensor 1

DTC P0140: HO2S Circuit Insufficient Activity Bank 1 Sensor 2

DTC P1133: HO2S Insufficient Switching Bank 1 Sensor 1

DTC P2A00: HO2S Circuit Closed Loop (CL) Performance Bank 1 Sensor 1

DTC P2A01: HO2S Circuit Closed Loop (CL) Performance Bank 1 Sensor 2

Diagnostic Fault Information

HO2S Bank 1 Sensor 1

Circuit

Short to Ground

High Resistance

Open

Short to Voltage

Signal Performance

HO2S High Signal

P0131, P0171, P1133, P2A00

P0131, P0133, P0134, P1133, P2A00

P0131, P0133, P0134, P1133, P2A00

P0132, P0134, P0172, P0300, P1133, P2A00

P0133, P0134, P1133, P2A00

HO2S Low Signal

P2A00

P0133, P0134, P1133, P1174, P2A00

P0133, P0134, P1133, P1174, P2A00

P0134, P1133, P2A00

P2A00

HO2S Bank 1 Sensor 2

Circuit

Short to Ground

High Resistance

Open

Short to Voltage

Signal Performance

HO2S High Signal

P0137, P0140, P2A01

P0140, P2A01

P0140, P2A01

P0138, P0140

P0140

HO2S Low Signal

--

P0140, P2A01

P0140, P2A01

P0138, P0140,

--

Typical Scan Tool Data

HO2S Bank 1 Sensor 1

HO2S Sensor Voltage Circuits

Normal Range

Short to Ground

Open

Short to Voltage

HO2S High Signal

0-1,000 mV

0-45 mV

350-550 mV

Approximately 1,100 mV

HO2S Low Signal

0-1,000 mV

0-1,000 mV

0-1,000 mV

0-1,100 mV

HO2S Bank 1 Sensor 2

HO2S Sensor Voltage Circuits

Normal Range

Short to Ground

Open

Short to Voltage

HO2S High Signal

0-1,000 mV

0-90 mV

Approximately 450 mV

Approximately 1,100 mV

HO2S Low Signal

0-1,000 mV

0-1,000 mV

450-700 mV

0-1,100 mV

Circuit/System 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 in the exhaust stream. The HO2S must reach operating temperature to provide an accurate voltage signal. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature. The engine control module (ECM) supplies the HO2S with a reference, or bias, voltage of about 450 mV. When the engine is first started, the ECM operates in Open Loop, ignoring the HO2S voltage signal. Once the HO2S reaches operating temperature and Closed Loop is achieved, the HO2S generates a voltage within a range of 0-1,000 mV that fluctuates above and below bias voltage. High HO2S voltage indicates a rich exhaust stream. Low HO2S voltage indicates a lean exhaust stream.

Conditions for Running the DTC

P0133

    • DTCs P0030, P0053, P0068, P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0128, P0131, P0132, P0134, P0135, P0201, P0202, P0203, P0204, P0205, P0206, P0220, P0222, P0223, P0300, P0442, P0443, P0446, P0449, P0451, P0452, P0453, P0454, P0455, P0496, P1516, P2101, P2119, P2135, P2176 are not set.
    • DTCs P0050, P0059, P0155, where applicable, are not set.
    • The system voltage is between 10-18 volts.
    • The scan tool special functions are not active.
    • The HO2S Bank 1 Sensor 1 Heater command parameter is ON for greater than 40 seconds.
    • The ECT sensor parameter is greater than 65°C (149°F).
    • The Intake Air Temperature (IAT) Sensor parameter is greater than -40°C (-40°F).
    • The Engine Run Time parameter is greater than 60 seconds.
    • The vehicle is not in Park, Reverse, or Neutral.
    • The Loop Status parameter is closed.
    • The MAF sensor parameter is between 17-37 g/s.
    • The TP Indicated Angle parameter is greater than 3.5 percent.
    • The Engine Speed parameter is between 1,250-2,550 RPM.
    • The evaporative emission (EVAP) system is purging.
    • The Barometric (BARO) parameter is at least 69.8 kPa.
    • The above conditions have been met for 3 seconds.

P0134

    • DTCs P0030, P0053, P0068, P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0451, P0452, P0453, P0454, P0455, P0496, P1516, P2101, P2119, P2135, P2176 are not set.
    • The system voltage is between 10-18 volts.
    • The scan tool special functions are not active.
    • The Engine Run Time parameter is greater than 2 minutes.

P0140 - Fast Pass Test

    • DTCs P0036, P0054, P0068, P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0451, P0452, P0453, P0454, P0455, P0496, P1516, P2101, P2119, P2135, P2176 are not set.
    • The system voltage is between 10-18 volts.
    • The scan tool special functions are not active.
    • The Engine Run Time parameter is less than 90 seconds.

P0140 - Regular Test

    • DTCs P0036, P0054, P0068, P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0451, P0452, P0453, P0454, P0455, P0496, P1516, P2101, P2119, P2135, P2176 are not set.
    • The system voltage is between 10-18 volts.
    • The FAST PASS Test has failed.
    • The scan tool special functions are not active.
    • The Engine Run Time parameter is greater than 124 seconds.
    • The TP Indicated Angle parameter has changed more than 3 percent at least 1 time.
    • The Loop Status parameter is closed.

P1133

    • DTCs P0030, P0053, P0068, P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0128, P0131, P0132, P0134, P0135, P0201, P0202, P0203, P0204, P0205, P0206, P0220, P0222, P0223, P0300, P0442, P0443, P0446, P0449, P0451, P0452, P0454, P0455, P0496, P1516, P2101, P2119, P2135, P2176, P2A00 are not set.
    • The system voltage is between 10-18 volts.
    • The scan tool special functions are not active.
    • The HO2S Bank 1 Sensor 1 Heater command parameter is ON for greater than 40 seconds.
    • The ECT Sensor parameter is greater than 65°C (149°F).
    • The IAT parameter is greater than -40°C (-40°F).
    • The Engine Run Time parameter is at least 60 seconds.
    • The EVAP purge solenoid is commanded ON.
    • The MAF sensor parameter is between 17-37 g/s.
    • The Engine Speed parameter is between 1,250-2,550 RPM.
    • The TP Indicated Angle parameter is greater than 3.5 percent.
    • The Loop Status parameter is closed.
    • The BARO parameter is at least 69.8 kPa.
    • The Fuel Level parameter is greater than 10 percent.
    • The vehicle is not in Park, Reverse, or Neutral.
    • The above conditions have been met for 3 seconds.

P2A00

    • DTCs  P0030, P0053, P0068, P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0120, P0121, P0122, P0123, P0128, P0131, P0132, P0133, P0134, P0135, P0151, P0152, P0153, P0154, P0201, P0202, P0203, P0204, P0205, P0206, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0451, P0452, P0453, P0454, P0455, P0496, P1133, P1153, P1516, P2101, P2119, P2176, P2A03 are not set.
    • The Engine Run Time parameter is more than 100 seconds.
    • The MAF Sensor parameter is between 5-30 g/s.
    • The Engine Speed parameter is between 500-3,000 RPM.
    • The ECT Sensor parameter is more than 65°C (149°F).
    • The DFCO parameter is Inactive.
    • The Power Enrichment (PE) parameter is Inactive.
    • The Ignition 1 Signal parameter is between 10-18 volts.
    • DTC P2A00 runs continuously when the above conditions are met for 5 seconds.

P2A01

    • DTCs P0030, P0053, P0068, P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0120, P0121, P0122, P0123, P0128, P0131, P0132, P0133, P0134, P0135, P0171, P0172, P0174, P0175, P0201, P0202, P0203, P0204, P0205, P0206, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0451, P0452, P0453, P0454, P0455, P0496, P1133, P1516, P2101, P2119, P2135, P2176, P2A00 are not set.
    • The engine is running for at least 5 minutes.
    • The ignition voltage is between 10-18 volts.
    • The Engine Speed parameter is between 625-1,650 RPM.
    • The MAF Sensor parameter is between 3.5-15 g/s.
    • The Vehicle Speed parameter is between 40-132 km/h (25-82 mph).
    • When all of the above conditions have been met for at least 2 seconds, the following conditions must also be met:
       - The evaporative emission (EVAP) purge diagnostic is not active.
       - The Short Term FT Bank 1 or the Short Term FT Bank 2 parameter is between +5 and -5 percent.
       - The Loop Status parameter is closed.
       - When all of the above conditions have been met for 4 seconds, the Intrusive portion of the test will be performed.

Conditions for Setting the DTC

P0133

    • The ECM detects that the HO2S 1 rich-to-lean and lean-to-rich transition time takes longer than a calibrated value.
    • Lean voltage threshold is 350 mV.
    • Rich voltage threshold is 600 mV.
    • This diagnostic runs once per trip.

P0134

    • The ECM detects that the HO2S 1 signal voltage is between 380-525 mV for more than 30 seconds.
    • This diagnostic runs continuously.

P0140 - Fast Pass Test

During the fast pass, the HO2S 2 voltage is between 350-550 mV for longer than 18 seconds within the first 90 seconds of engine run time. If the fast pass test does not report a pass, then the regular test is initiated.

P0140 - Regular Test

    • During the regular test, the HO2S 2 voltage is between 380-525 mV for at least 120 seconds.
    • This diagnostic runs once per trip.

P1133

    • The ECM detects that the HO2S 1 voltage did not have enough switches from rich-to-lean and lean-to-rich during a 70 second monitoring period.
    • This diagnostic runs once per trip.

P2A00

    • The ECM detects the loop status is open.
    • The ECM detects that the HO2S  1 voltage signal remains between 350-550 mV for more than 10 seconds.
    • This diagnostic runs continuously.

P2A01

    • The HO2S 2 parameter is between 175-715 mV during the passive test.
    • One of the following tests fail:
       - Lean Intrusive Test--Accumulated mass air flow is greater than 400 grams and HO2S 2 voltage signal is less than 175 mV.
       - Rich Intrusive Test--Accumulated mass air flow is greater than 600 grams and HO2S 2 voltage signal is greater than 715 mV.
    • This diagnostic runs up to 8 times per trip, or once per trip on a pass.

Action Taken When the DTC Sets

DTCs P0133, P0134, P0140, P1133, P2A00, and P2A01 are Type B DTCs.

Conditions for Clearing the MIL/DTC

DTCs P0133, P0134, P0140, P1133, P2A00, and P2A01 are Type B DTCs.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs
    •  Heated Oxygen Sensor Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification
  1. If any HO2S heater DTCs are set, perform those diagnostics first.
  2. Allow the engine to reach operating temperature.
  3. Engine running, observe the affected HO2S parameter with a scan tool.
    4. ⇒The pre-catalyst oxygen sensors value should vary from below 200 mV to above 800 mV and respond to fueling changes.
    ⇒The post-catalyst oxygen sensors value should change more than 200 mV when the throttle is quickly cycled 3 times from closed to wide open and back to closed after running the engine at 1,500 RPM for 30 seconds.
  4. The affected HO2S may be damaged due to contamination. Prior to replacing the affected HO2S, inspect for the following sources of contamination.

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

    • A silicon contaminated HO2S
    • Fuel contamination--Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Engine oil consumption--Refer to Oil Consumption Diagnosis .
    • Engine coolant consumption--Refer to Loss of Coolant .
  5. 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 data.

Circuit/System Testing

Important: All modules must be powered down or misdiagnosis may result.

  1. Ignition OFF, disconnect the scan tool and wait 60 seconds to ensure all modules are powered down.
  2. Ignition OFF, disconnect the harness connector at the appropriate HO2S.
  3. Ignition OFF, measure for less than 5 ohms resistance between the appropriate HO2S low signal circuit terminal A and ground.
    4. ⇒If more than the specified range, test the appropriate HO2S low signal circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
  4. Ignition ON, verify the appropriate scan tool HO2S parameter is approximately 450 mV.
    5. ⇒If more than the specified value, test the appropriate HO2S high signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.
    ⇒If less than the specified value, test the appropriate HO2S high signal circuit for a short to ground. If the circuit tests normal, replace the ECM.
  5. Ignition ON, install a 3A fused jumper wire at the HO2S high signal circuit terminal B. Toggle the jumper wire between the HO2S low signal circuit terminal A and battery voltage. Verify the appropriate scan tool HO2S parameter toggles between 0 mV and approximately 1,000 mV.
    6. ⇒If the appropriate scan tool HO2S parameter does not toggle correctly, test the HO2S high signal circuit for an open/high resistance. If the circuits test normal, replace the ECM.
  6. If all circuits test normal, replace the appropriate HO2S.

Repair Instructions

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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Heated Oxygen Sensor Replacement - Bank 1 Sensor 1
    •  Heated Oxygen Sensor Replacement - Bank 1 Sensor 2
    •  Control Module References for ECM replacement, setup, and programming