GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2006 🢒 STS 🢒 DTC 🢒 DTC P0131, P0132, P0137, P0138, P0151, P0152, P0157, P0158, P2A00, P2A01, P2A03, or P2A04

DTC Descriptors

DTC P0131: HO2S Circuit Low Voltage Bank 1 Sensor 1

DTC P0132: HO2S Circuit High Voltage Bank 1 Sensor 1

DTC P0137: HO2S Circuit Low Voltage Bank 1 Sensor 2

DTC P0138: HO2S Circuit High Voltage Bank 1 Sensor 2

DTC P0151: HO2S Circuit Low Voltage Bank 2 Sensor 1

DTC P0152: HO2S Circuit High Voltage Bank 2 Sensor 1

DTC P0157: HO2S Circuit Low Voltage Bank 2 Sensor 2

DTC P0158: HO2S Circuit High Voltage Bank 2 Sensor 2

DTC P2A00: HO2S Performance Bank 1 Sensor 1

DTC P2A01: HO2S Performance Bank 1 Sensor 2

DTC P2A03: HO2S Performance Bank 2 Sensor 1

DTC P2A04: HO2S Performance Bank 2 Sensor 2

Diagnostic Fault Information

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

Circuit

Short to Ground

High Resistance

Open

Short to Voltage

Signal Performance

HO2S High Signal

P0131, P0132, P0134, P0137, P0140, P0151, P0154, P0157, P0160, P1133, P1153, P2A00, P2A01, P2A03, P2A04

P0131, P0133, P0134, P0137, P0140, P0151, P0153, P0154, P0157, P0160, P1133, P1153, P2A00, P2A01, P2A03, P2A04

P0131, P0133, P0134, P0137, P0140, P0153, P0154, P1133, P1153, P2A00, P2A01, P2A03, P2A04

P0132, P0134, P0138, P0140, P0152, P0154, P0158, P0160, P1133, P1153, P2A00, P2A01, P2A03, P2A04

P0133, P0134, P0140, P0153, P0160, P1133, P1153, P2A00, P2A01, P2A03, P2A04

HO2S Low Signal

P2A00, P2A01, P2A03, P2A04

P0131, P0133, P0134, P0138, P0140, P0151, P0153, P0154, P0157, P0160, P1133, P1153, P2A00, P2A01

P0131, P0133, P0134, P0138, P0140, P0153, P0154, P1133, P1153, P2A00, P2A01, P2A03, P2A04

P0134, P0138, P0140, P0152, P0153, P0158, P0160, P1133, P1153, P2A00, P2A01, P2A03, P2A04

P2A00, P2A01, P2A03, P2A04

Typical Scan Tool Data

HO2S Sensor 1 Voltage

Circuit

Normal Range

Short to Ground

Open

Short to Voltage

HO2S High Signal

200-800 mV

0 mV

Approximately 470 mV

Approximately 1,100 mV

HO2S Low Signal

200-800 mV

455 mV

Approximately 450 mV

Approximately 445 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 control module supplies the HO2S with a reference, or bias, voltage of about 450 mV. When the engine is first started, the control module 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

P0131

    • DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0455, P0496, P1516, P2101, P2119, P2135, P2176 are not set.
    • The Loop Status parameter is Closed.
    • The Ignition 1 Signal parameter is between 10-18 volts.
    • The Fuel Tank Level Remaining parameter is more than 10 percent.
    • The Throttle Position (TP) Indicated Angle parameter is between 0-50 percent.
    • The equivalence ratio is between 0.99-1.01.
    • DTC P0131 runs the lean test continuously when the above conditions are met for 3 seconds.

P0132

    • DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0455, P0496, P1516, P2101, P2119, P2135, P2176 are not set.
    • The Loop Status parameter is Closed.
    • The Ignition 1 Signal parameter is between 10-18 volts.
    • The Fuel Tank Level Remaining parameter is more than 10 percent.
    • The Throttle Position (TP) Sensor parameter is between 0-60 percent.
    • The equivalence ratio is between 0.99-1.01.
    • DTC P0132 runs the rich test continuously when the above conditions are met for 3 seconds.

P0137 or P0157

    • DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0455, P0496, P1516, P2101, P2119, P2135, P2176 are not set.
    • The Loop Status parameter is Closed.
    • The Ignition 1 Signal parameter is between 10-18 volts.
    • The Fuel Tank Level Remaining parameter is more than 10 percent.
    • The Power Enrichment parameter is active for more than 3 seconds.
    • The equivalence ratio is between 0.99-1.01.
    • These DTCs run the power enrichment test during each occurrence of power enrichment, when the above conditions are met for 3 seconds.

P0138 or P0158

    • DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0455, P0496, P1516, P2101, P2119, P2135, P2176 are not set.
    • The Loop Status parameter is Closed.
    • The Ignition 1 Signal parameter is between 10-18 volts.
    • The Fuel Tank Level Remaining parameter is more than 10 percent.
    • The TP Sensor parameter is between 0-50 percent.
    • The equivalence ratio is between 0.99-1.01.
    • These DTCs run the rich test continuously when the above conditions are met for 3 seconds.

P0151

    • DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0455, P0496, P1516, P2101, P2119, P2135, P2176 are not set.
    • The Loop Status parameter is Closed.
    • The Ignition 1 Signal parameter is between 10-18 volts.
    • The Fuel Tank Level Remaining parameter is more than 10 percent.
    • The Throttle Position (TP) Sensor parameter is between 0-50 percent.
    • The equivalence ratio is between 0.99-1.01.
    • DTC P0151 runs the test continuously when the above conditions are met for 3 seconds.

P0152

    • DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0455, P0496, P1516, P2101, P2119, P2135, P2176 are not set.
    • The Loop Status parameter is Closed.
    • The Ignition 1 Signal parameter is between 10-18 volts.
    • The Fuel Tank Level Remaining parameter is more than 10 percent.
    • The Throttle Position (TP) Sensor parameter is between 0-60 percent.
    • The equivalence ratio is between 0.99-1.01.
    • DTC P0152 runs the test continuously when the above conditions are met for 3 seconds.

P2A00

    • DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0455, P0496, P1516, P2101, P2119, P2135, P2176 are not set.
    • The Engine Run Time parameter is more than 100 seconds.
    • The Engine speed parameter is between 500-5,000 RPM.
    • The Ignition 1 Signal parameter is between 10-18 volts.
    • The Mass Airflow (MAF) Sensor parameter is between 3-30 g/s.
    • The ECT Sensor parameter is more than 70°C (158°F).
    • DTC P2A00 runs continuously when the above conditions are met for 5 seconds.

P2A01 or P2A04 Passive Test

    • DTCs P0030, P0036, P0053, P0054, P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0128, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0140, P0141, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0455, P0496, P1133, P1516, P2101, P2119, P2135, P2176, P2A00 are not set.
    • The engine is running.
    • The Engine Run Time parameter is less than 260 seconds.
    • These DTCs run the passive test once per drive cycle when the above conditions are met for 2 seconds.

P2A01 or P2A04 Intrusive Test

    • DTCs P0030, P0036, P0053, P0054, P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0128, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0140, P0141, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0455, P0496, P1133, P1516, P2101, P2119, P2135, P2176, P2A00 are not set.
    • The Engine Run Time parameter is more than 260 seconds.
    • The ignition 1 Signal parameter is between 10-18 volts.
    • The MAF sensor parameter is between 0.5-50 g/s.
    • The Engine Speed parameter is between 500-5,000 RPM.
    • The Vehicle Speed parameter is between 24-145 km/h (20-80 mph).
    • The Short Term FT parameter is between 5 and -5 percent.
    • These DTCs run the intrusive test once per drive cycle when the above conditions are met for 1 second.

P2A03

    • DTCs P0030, P0036, P0053, P0054, P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0128, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0140, P0141, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0455, P0496, P1133, P1516, P2101, P2119, P2135, P2176, P2A00 are not set.
    • The Engine Run Time parameter is more than 100 seconds.
    • The ignition 1 Signal parameter is between 10-18 volts.
    • The MAF sensor parameter is between 3-30 g/s.
    • The Engine Speed parameter is between 500-5,000 RPM.
    • DTC P2A01 runs continuously when the above conditions are met for 5 seconds.

Conditions for Setting the DTC

P0131

    • The control module detects that the HO2S 1 Voltage parameter is less than 25 mV.
    • DTC P0131 sets within 100 seconds during the lean test when the above condition is met.

P0132

    • The control module detects that the HO2S 1 parameter is more than 950 mV.
    • DTC P0132 sets within 15 seconds during the rich test when the above condition is met.

P0137 or P0157 Lean Test

    • The control module detects that the HO2S 2 voltage parameter is less than 75 mV.
    • These DTCs set within 100 seconds during the lean test when the above condition is met.

P0138 or P0158 Rich Test

    • The control module detects that the HO2S 2 voltage parameter is more than 950 mV.
    • These DTCs set within 100 seconds during the rich test when the above condition is met.

P0151

    • The control module detects that the HO2S Bank 2 Sensor 1 Voltage parameter is less than 100 mV.
    • DTC P0151 sets within 3 seconds when the above condition is met.

P0152

    • The control module detects that the HO2S Bank 2 Sensor 1 Voltage parameter is more than 950 mV.
    • DTC P0151 sets within 3 seconds when the above condition is met.

P2A00 or P2A03

    • The control module detects that the Loop Status parameter is open.
    • These DTCs set within 5 seconds when the above condition is met.

P2A01 or P2A04

    • The control module detects that the HO2S 2 did not transition below 299 mV and above 751 mV during the passive test.
    • One of the following tests fail once per trip/runs until pass or fail reporting:
       - Lean Intrusive Test--The control module detects that the HO2S 2 is more than 751 mV for 8 seconds.
       - Rich Intrusive Test--The control module detects that the HO2S 2 is less than 299 mV for 8 seconds.
    • These DTCs set sets within 2 minutes when the above conditions are met.
    • The control module detects that the Loop Status parameter is open by not meeting the voltage criteria to enable close loop fueling.
        Voltage cannot be between 250-600 mV for 10 seconds after the O2 has seen a ready to go closed loop command.
    • These DTCs set within 5 seconds when the above condition is met.

Action Taken When the DTC Sets

DTC P0131, P0132, P0137, P0138, P0151, P0152, P0157, P0158, P2A00, P2A01, P2A03, P2A04 are Type B DTCs.

Conditions for Clearing the MIL/DTC

DTC P0131, P0132, P0137, P0138, P0151, P0152, P0157, P0158, P2A00, P2A01, P2A03, P2A04 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

Circuit/System Verification
    • If any HO2S heater DTCs are set, perform those diagnostics first.
    • Allow the engine to reach operating temperature.
    •  Engine running, observe the affected HO2S parameter with a scan tool.
       - 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.
    • The affected HO2S may be damaged due to contamination. Prior to replacing the affected HO2S, inspect for the following sources of contamination:

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 .

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