The wide band heated oxygen sensor (HO2S) measures the amount of oxygen in the exhaust system and provides more information than the switching style HO2S. The wide band sensor consists of an oxygen sensing cell, an oxygen pumping cell, and a heater. The exhaust gas sample passes through a diffusion gap between the sensing cell and the pumping cell. The engine control module (ECM) supplies a voltage to the HO2S and uses this voltage as a reference to the amount of oxygen in the exhaust system. An electronic circuit within the ECM controls the pump current through the oxygen pumping cell in order to maintain a constant voltage in the oxygen sensing cell. The ECM monitors the voltage variation in the sensing cell and attempts to keep the voltage constant by increasing or decreasing the amount of current flow, or oxygen ion flow, to the pumping cell. By measuring the amount of current required to maintain the voltage in the sensing cell, the ECM can determine the concentration of oxygen in the exhaust. The HO2S voltage is displayed as a lambda value. A lambda value of 1 is equal to a stoichiometric air fuel ratio of 14.7:1. Under normal operating conditions, the lambda value will remain around 1. When the fuel system is lean, the oxygen level will be high and the lambda signal will be high or more than 1. When the fuel system is rich, the oxygen level will be low, and the lambda signal will be low or less than 1. The ECM uses this information to maintain the correct air/fuel ratio.

DTC P2231 is a Type B DTC.

DTC P2231 is a Type B DTC.

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

The following table illustrates the ECM connector locations:

1. Ignition ON, observe the scan tool DTC information. Verify that DTCs P0131, or P0132 are not set.

⇒	If any of the listed DTCs are set refer to DTC P0131 or DTC P0132 for further diagnosis.

2. Engine idling at operating temperature. Observe the scan tool Loop Status Sen 1. Verify the scan tool displays Closed Loop.
3. Operate the vehicle within the conditions for running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records Data List.

1. Ignition OFF, disconnect the harness connector at the HO2S 1.
2. Ignition ON, test for 2.5-3.5 volts between the high signal circuit terminal 1 and ground.

⇒	If greater than the specified range, test the high signal circuit for a short to the heater control circuit. If the circuit tests normal, replace the ECM.

3. Test for 2-3 volts between the low signal circuit terminal 5 and ground

⇒	If greater than the specified range, test the low signal circuit for a short to the heater control circuit. If the circuit tests normal, replace the ECM.

Important: The input pumping current circuit and the pump current circuit are connected internally within the ECM. If there is a condition with one of the circuits, the other circuit will be affected.

4. Test for less than 1 volt between the input pump circuit terminal 6 and ground.

⇒	If greater than the specified range, test the input pump circuit and pump current circuit for a short to the heater control circuit. If the circuit tests normal, replace the ECM.

5. If all circuits test normal, replace the HO2S 1.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.