P0032

DTC P0031, P0032, P0037, or P0038

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
* Strategy Based Diagnosis Strategy Based Diagnosis
* Diagnostic Procedure Instructions Diagnostic Procedure Instructions

DTC Descriptors
DTC P0031
- HO2S Heater Control Circuit Low Voltage Sensor 1

DTC P0032
- HO2S Heater Control Circuit High Voltage Sensor 1

DTC P0037
- HO2S Heater Control Circuit Low Voltage Sensor 2

DTC P0038
- HO2S Heater Control Circuit High Voltage Sensor 2

Diagnostic Fault Information






Circuit Description

The 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. A heating element inside the HO2S minimizes the time required for the sensor to reach operating temperature. Voltage is provided to the heater by the ignition 1 voltage circuit through a fuse. Ground is provided to the heater on the low control circuit by a low side driver within the control module.

The HO2S utilizes the following circuits:

* A signal circuit
* A low reference circuit
* An ignition 1 voltage circuit
* A heater control circuit

Conditions for Running the DTC

* The engine is running.
* The ignition 1 voltage is between 7.5-16 volts.
* The DTC runs continuously when the above conditions are met.

Conditions for Setting the DTC

The engine control module (ECM) detects an open, short to ground, or short to voltage on the control circuit of the H02S.

Action Taken When the DTC Sets

* DTC P0031, P0032, P0037, and P0038 are Type A DTCs.
* The ECM commands the fuel control system to open loop.

Conditions for Clearing the MIL/DTC

DTC P0031, P0032, P0037, and P0038 are Type A DTCs.

Reference Information

Schematic Reference

Engine Controls Schematics (w/Throttle Actuator Controls) Electrical DiagramsEngine Controls Schematics (w/o Throttle Actuator Control) Electrical Diagrams

Connector End View Reference
* Engine Control Module Connector End Views (w/ Throttle Actuator Control) Engine Control Module Connector End Views (w/ Throttle Actuator Control)Engine Control Module Connector End Views (w/o Throttle Actuator Control) Engine Control Module Connector End Views (w/o Throttle Actuator Control)
* Engine Controls Connector End Views (w/ Throttle Actuator Control) Engine Controls Connector End Views (w/ Throttle Actuator Control)Engine Controls Connector End Views (w/o Throttle Actuator Control) Engine Controls Connector End Views (w/o Throttle Actuator Control)

Electrical Information Reference
* Circuit Testing Circuit Testing
* Connector Repairs Connector Repairs
* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference
* Scan Tool Data List (w/ Throttle Actuator Control) Scan Tool Data List (w/ Throttle Actuator Control)Scan Tool Data List (w/o Throttle Actuator Control) Scan Tool Data List (w/o Throttle Actuator Control)
* Scan Tool Data Definitions (w/ Throttle Actuator Control) Scan Tool Data Definitions (w/ Throttle Actuator Control)Scan Tool Data Definitions (w/o Throttle Actuator Control) Scan Tool Data Definitions (w/o Throttle Actuator Control)
* Scan Tool Output Controls (w/ Throttle Actuator Control) Scan Tool Output Controls (w/ Throttle Actuator Control)Scan Tool Output Controls (w/o Throttle Actuator Control) Scan Tool Output Controls (w/o Throttle Actuator Control)

Circuit/System Verification

Important: It may take up to 8 minutes for the DTC to set.


1. With the engine at normal operating temperature, operate the engine above 1,200 RPM for 30 seconds and then allow the engine to idle. DTC P0031, P0032, P0037, or P0038 should not set.
2. If the vehicle passes the Circuit/System Verification Test, then operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records Data List.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the appropriate heated oxygen sensor (HO2S).
2. Ignition ON, verify that a test lamp illuminates between the ignition 1 voltage circuit and ground.

• If the test lamp does not illuminate, test the ignition 1 voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition 1 voltage circuit fuse is open, test all components connected to the ignition 1 voltage circuit and replace as necessary.

3. Ignition OFF, connect a test lamp between the control circuit and B+.
4. Ignition ON, command the HO2S Heater ON and OFF with a scan tool. The test lamp should turn ON and OFF.

• If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit/connections test normal, replace the ECM.
• If the test lamp is always ON, test the control circuit for a short to ground. If the circuit/connections test normal, replace the ECM.

5. If all circuits/connections test normal, test or replace the HO2S sensor.

Component Testing

1. Ignition OFF, disconnect the harness connector of the HO2S.
2. Measure for 3-23 ohms of resistance between the ignition 1 voltage circuit terminal and the control circuit terminal of the HO2S heater.

• If the resistance is out of the specified range, replace the HO2S sensor.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.

* Heated Oxygen Sensor 1 Replacement Heated Oxygen Sensor 1 Replacement
* Heated Oxygen Sensor 2 Replacement Heated Oxygen Sensor 2 Replacement
* Control Module References Control Module References for engine control module replacement, setup, and programming