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For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2008 🢒 SLS 🢒 Diagnostic Navigation 🢒 Vehicle Diagnostic Information 🢒 DTC P0131, P0132, P0137, or P0138

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 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

Diagnostic Fault Information

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

Short to Ground

Open

Short to Voltage

Parameter Normal Range: 200-800 mV

HO2S High Signal

0 mV

Approximately 470 mV

Approximately 1,100 mV

HO2S Low Signal

455 mV

Approximately 450 mV

Approximately 445 mV

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 in the exhaust gases. The HO2S must reach operating temperature to provide an accurate voltage signal. A heating element inside the HO2S minimizes the time required for the sensor to reach operating temperature. The control module supplies the HO2S with a reference, reference voltage or bias voltage of approximately 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 activated, 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 gases. Low HO2S voltage indicates a lean exhaust gases.

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, P1101, P1516, P2101, P2119, P2135, P2176 are not set.
    • The three-way catalytic monitor intrusive diagnostic tests is inactive.
    • The post oxygen sensor intrusive diagnostic tests is inactive.
    • The traction control, induction, fuel, idling, exhaust gas recirculation and engine no overspeed intrusive test is inactive.
    • The EGR valve, idling, fuel inject and intake air output control is inactive.
    • The HO2S Loop Status parameter is Closed.
    • The Ignition 1 Signal parameter is between 10-18 volts.
    • The TP indicated angle parameter is 0-50 percent.
    • The equivalent ratio is between 0.99-1.01.
    • The fuel injectors is in the open state.
    • The traction control is inactive.
    • 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, P1101, P1516, P2101, P2119, P2135, P2176 are not set.
    • The three-way catalytic monitor intrusive diagnostic tests is inactive.
    • The post oxygen sensor intrusive diagnostic tests is inactive.
    • The traction control, induction, fuel, idling, exhaust gas recirculation and engine no overspeed intrusive test is inactive.
    • The EGR valve, idling, fuel inject and intake air output control is inactive.
    • The HO2S Loop Status parameter is Closed.
    • The ignition 1 Signal parameter is between 10-18 volts.
    • The Throttle Position (TP) Sensor parameter is between 0-60 percent.
    • The equivalent ratio is between 0.99-1.01.
    • The fuel injectors is in the open state.
    • The traction control is inactive.
    • DTC P0132 runs the rich test continuously when the above conditions are met for 3 seconds.

P0137 and P0138

    • 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, P1101, P1516, P2101, P2119, P2135, P2176 are not set.
    • The three-way catalytic monitor intrusive diagnostic tests is inactive.
    • The post oxygen sensor intrusive diagnostic tests is inactive.
    • The traction control, induction, fuel, idling, exhaust gas recirculation and engine No overspeed intrusive test is inactive.
    • The EGR valve, idling, fuel inject and intake air output control is inactive.
    • The HO2S Loop Status parameter is Closed.
    • The ignition 1 signal parameter is between 10-18 volts.
    • The throttle position (TP) indicated angle parameter is between 0-50 percent.
    • The equivalent ratio is between 0.99-1.01.
    • The fuel injectors is in the open state.
    • The traction control is inactive.
    • These DTCs run the power enrichment test during each occurrence of power enrichment, when the above conditions are met for 3 seconds.

Conditions for Setting the DTC

P0131

    • The control module detects that the HO2S 1 voltage parameter is less than 25 mV.
        OR
    • The control module detects that the HO2S Bank 1 Sensor 2 Voltage parameter is less than 10 mV.
    • It occurs 160 times faults during every 200 times tests for 2 consecutive test experiment.
    • DTC P0131 is set when the above conditions are met.

P0132

    • The control module detects that the HO2S 1 parameter is more than 1,050 mV.
    • It occurs 40 times faults during every 50 times tests for 2 consecutive test experiment.
    • DTC P0132 is set when the above conditions are met.

P0137 Lean Test

    • It occurs 320 times faults during every 400 times tests for 1 consecutive test experiment.
    • DTC P0137 is set when the above condition is met.

P0138 Rich Test

    • The control module detects that the HO2S 2 voltage parameter is more than 1,050 mV.
    • It occurs 320 times faults during every 400 times tests for 1 consecutive test experiment.
    • DTC P0138 is set when the above conditions are met.

Action Taken When the DTC Sets

DTCs P0131 P0132, P0137 and P0138 are Type B DTCs.

Conditions for Clearing the DTC

DTCs P0131 P0132, P0137 and P0138 are Type B DTCs.

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

    •  Engine Controls Connector End Views
    •  Engine Control Module Connector End Views

Electrical Information Reference

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

DTC Type Reference

Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Scan Tool Data List

Circuit/System Verification
    • If any HO2S DTCs are set, diagnose those DTCs first.
    • Allow the engine to reach operating temperature.
    • With the 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 the throttle 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.

       - Silicon Contamination of 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. Turn the ignition OFF, disconnect the scan tool and wait 60 seconds to ensure all modules are powered down.
  2. Turn the ignition OFF, disconnect the harness connector at the appropriate HO2S sensor.
  3. Ignition OFF, test for less than 5 ohms between the appropriate heated oxygen sensor low reference 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 test 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 test 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 test normal, replace the ECM.
  5. Ignition ON, install a 3-amp fused jumper wire at the HO2S high signal circuit terminal B. Secure the jumper wire between the HO2S low signal circuit terminal A and battery voltage. Verify that the appropriate scan tool HO2S parameter changes between 0 mV and approximately 1,000 mV.
    6. ⇒If the appropriate scan tool HO2S parameter does not change correctly, test the HO2S high signal circuit for an open/ high resistance. If the circuit 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