GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2007 🢒 Solstice 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 DTC P0137, P0138, P0139, P0140, P2232, P2270, or P2271

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 provides an overview of each diagnostic category.

DTC Descriptors

DTC P0137: HO2S Circuit Low Voltage Sensor 2

DTC P0138: HO2S Circuit High Voltage Sensor 2

DTC P0139: HO2S Slow Response Sensor 2

DTC P0140: HO2S Circuit Insufficient Activity Sensor 2

DTC P2232: HO2S Signal Circuit Shorted to Heater Circuit Sensor 2

DTC P2270: HO2S Signal Stuck Lean Sensor 2

DTC P2271: HO2S Signal Stuck Rich Sensor 2

Diagnostic Fault Information

Circuit

Short to Ground

Open

Short to Voltage

Signal Performance

HO2S 2 Heater Voltage Supply

Opens fuse

P0036, P0037, P0141

--

P0141

HO2S 2 Heater Low Control

P0036, P0037,

P0036, P0037, P0141

P0036, P0038, P0141

P0141

HO2S 2 Signal Hi

P0137

--

P0138

--

HO2S 2 Reference Ground

--

--

--

--

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

P0137 Lean Test Enable

    • DTCs P0116, P0117, P0118, P0119, P0125 are not set.
    • The Ignition 1 Signal parameter is between 10-18 volts.
    • Modeled exhaust gas temp model is more than 250°C (482°F) for at least 90 seconds.
    • Modeled exhaust gas temp model is less than 800°C (1,472°F).
    • Time after engine start is less than 1 second.
    • Engine coolant is more than 60°C (140°F) after last engine shut-down.
    • Engine coolant at start is less than 40°C (104°F)
    • DTC P0137 runs once per drive cycle when the above conditions are met for 2 seconds.

P0138 Rich Test Enable

    • DTCs P0116, P0117, P0118, P0119, P0125 are not set.
    • The Loop Status parameter is Closed.
    • The Ignition 1 Signal parameter is between 10-18 volts.
    • Modeled exhaust gas temp model is more than 250°C (482°F) for at least 90 seconds.
    • Modeled exhaust gas temp model is less than 800°C (1,472°F).
    • DTC P0138 runs the rich test continuously when the above conditions are met for 2 seconds.

P0139

    • DTCs P0137, P0138, P0140, P2232, P2270, P2271 are not set.
    • Deceleration Fuel Cut-Off (DFCO) is active.
    • HO2S 2 voltage since DFCO is more than 0.59 mV.
    • Ignition voltage is more than 10.5 volts.
    • Total integrated air mass during test must exceed 20 g.
    • DTC P0139 runs continuously when the above conditions are met for 2 seconds.

P0140

    • DTCs P0116, P0117, P0118, P0119, P0125 are not set.
    • The engine is running.
    • The HO2S 2 heater is stable and the estimated exhaust temperature was more than 250°C (482°F) for more than 90 seconds.
    • Ignition voltage is more than 10.5V.
    • Estimated exhaust temperature is less than 800°C (1,472°F).
    • DTC P0140 runs continuously when the above conditions are met for 60 seconds.

P2232

    • DTCs P0116, P0117, P0118, P0119, P0125 are not set.
    • The engine is running.
    • The HO2S 2 heater is stable and the estimated exhaust temperature was more than 250°C (482°F) for more than 90 seconds.
    • Ignition voltage is more than 10.5V.
    • Estimated exhaust temperature is less than 800°C (1,472°F).
    • DTC P2232 runs continuously when the above conditions are met for 60 seconds.

P2270

    • DTCs P0036, P0037, P0038, P0137, P0138, P0140, P0141, P0443, P0458, P0459, P2232 are not set.
    • The engine is running.
    • Ignition voltage is more than 10.5V.
    • The HO2S 2 has been in closed loop for more than 10 seconds.
    • DFCO is inactive.
    • Engine air flow has been between 5.56-33.33 g/sec for more than 3 seconds and is currently more than 9.72 g/sec.
    • DTC P2270 runs continuously when the above conditions are met for 10 minutes.

P2271

    • DTCs P0036, P0037, P0038, P0137, P0138, P0140, P0141, P0443, P0458, P0459, P2232 are not set.
    • The engine is running.
    • Ignition voltage is more than 10.5V.
    • The HO2S 2 has been in closed loop for more than 10 seconds.
    • DFCO is inactive.
    • Engine air flow has been between 5.56-33.33 g/sec for more than 3 seconds and is currently more than 9.72 g/sec.
    • DTC P2271 runs continuously when the above conditions are met for 10 minutes.

Conditions for Setting the DTC

P0137

    • The ECM detects that the HO2S 2 voltage parameter is less than 60 mV.
    • DTC P0137 sets within 0.1 second during the lean test when the above condition is met.

P0138

    • The ECM detects that the HO2S 2 voltage parameter is more than 1,050 mV.
    • DTC P0138 sets within 0.1 second during the rich test when the above condition is met.

P0139

    • The ECM detects that the HO2S 2 voltage parameter is more than 0.11 volt since DFCO.
    • DTC P0139 sets within 4 seconds when the above condition is met.

P0140

    • The ECM detects that the HO2S 2 voltage parameter is between 0.401-0.519 volt OR that the HO2S 2 internal resistance is more than 40,000 ohms while the calculated exhaust temperature is more than 600°C (1,112°F).
    • DTC P0140 sets within 4 seconds when the above condition is met for 60 seconds.

P2232

    • The ECM detects that the HO2S 2 voltage and the HO2S 2 heater voltage changes are synchronous.
    • DTC P2232 sets within 4 seconds when the above condition is met continuously, or within 50 seconds when the above condition is met cumulatively.

P2270

    • The ECM detects that the HO2S 2 voltage oscillations are slower than a calibrated value.
    • DTC P2270 sets within 4 seconds when the above condition is met continuously, or within 50 seconds when the above condition is met cumulatively.

P2271

    • The ECM detects that the HO2S 2 voltage oscillations are faster than a calibrated value.
    • DTC P2271 sets within 4 seconds when the above condition is met continuously, or within 50 seconds when the above condition is met cumulatively.

Action Taken When the DTC Sets

DTC P0137, P0138, P0139, P0140, P2232, P2270, and P2271 are Type B DTCs.

Conditions for Clearing the MIL/DTC

DTC P0137, P0138, P0139, P0140, P2232, P2270, and P2271 are Type B DTCs.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

    •  Engine Control Module Connector End Views
    •  Engine Controls 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

    •  Scan Tool Data List
    •  Scan Tool Data Definitions
    •  Scan Tool Output Controls

Circuit/System Verification
  1. Clear the DTCs with a scan tool.
  2. Operate the vehicle within the conditions for running and setting the DTC. The DTC should not set.

Circuit/System Testing

You must perform the Circuit/System Verification before proceeding with 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 HO2S 2.
  3. Ignition OFF, measure for less than 5 ohms resistance between the HO2S 2 low signal circuit terminal A and ground.
    4. ⇒If more than the specified range, test the HO2S 2 low signal circuit for an open/high resistance. If the circuit tests normal, replace the ECM.
  4. Ignition ON, verify the scan tool HO2S 2 parameter is approximately 450 mV.
    5. ⇒If more than the specified value, test the HO2S 2 high signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.
    ⇒If less than the specified value, test the HO2S 2 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 2 high signal circuit terminal B. Toggle the jumper wire between the HO2S 2 low signal circuit terminal A and battery voltage. Verify the scan tool HO2S 2 parameter toggles between 0 mV and approximately 1,000 mV.
    6. ⇒If the scan tool HO2S 2 parameter does not toggle correctly, test the HO2S 2 high signal circuit for an open/high resistance. If the circuits test normal, replace the ECM.
  6. If all circuits test normal, replace the HO2S 2.

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.

       Important: For DTC P0131 and P0132, in order to ensure that the performance of the catalyst has not been affected by the fault that set this DTC, operate the vehicle within the conditions for running and setting DTC P0420 and verify that P0420 runs and passes. Refer to DTC P0420 .

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