For 1990-2009 cars

### 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 P0041: HO2S Signals Swapped Banks 1 and 2 Sensor 2

### Circuit Description

The heated oxygen sensors (HO2S) are used for fuel control and catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the engine is started, the control module operates in an Open Loop mode, ignoring the HO2S signal voltage while calculating the air-to-fuel ratio. The control module supplies the HO2S with a reference, or bias voltage of about 450 mV. While the engine runs, the HO2S heats up and begins to generate a voltage within a range of 0-1,000 mV. This voltage will fluctuate above and below the bias voltage. Once sufficient HO2S voltage fluctuation is observed by the control module, Closed Loop is entered. The control module uses the HO2S voltage to determine the air-to-fuel ratio. An HO2S voltage that increases above bias voltage toward 1,000 mV indicates a rich fuel mixture. An HO2S voltage that decreases below bias voltage toward 0 mV indicates a lean fuel mixture. If the ECM detects that the HO2S signals are the opposite of the commanded air/fuel ratio for both banks, this DTC sets.

### Conditions for Running the DTC

• | The engine is operating.

• | The rear heated oxygen sensors are in closed loop.

• | The ECM is commanding the secondary rear heated oxygen sensor fuel trim control.

• | DTC P0041 runs continuously once the above conditions are met.

### Conditions for Setting the DTC

• | The ECM detects that the rear HO2S voltage for 1 bank of the engine is more than 680 mV while the other rear HO2S is less than 150 mV.

• | The above conditions exists for more than 80 seconds.

### Action Taken When the DTC Sets

DTC P0041 is a Type B DTC.

### Conditions for Clearing the MIL/DTC

DTC P0041 is a Type B DTC.

### Diagnostic Aids

This diagnostic detects if the rear heated oxygen sensors are not connected to the correct bank of the engine.

### 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

#### 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. Ignition ON, observe the DTC information with a scan tool. Verify no other HO2S DTCs are set.

⇒ | If a DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .

2. Operate the engine at 1500 RPM for two minutes. Observe the DTC information with a scan tool. DTC P0041 should not set.

⇒ | If the DTC failed this ignition, switch the HO2S Bank 1 Sensor 2 harness connector with the HO2S Bank 2 Sensor 2 harness connector.

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 you observed from the Freeze Frame/Failure Records data.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Heated Oxygen Sensor Replacement - Bank 1 Sensor 2

• | Heated Oxygen Sensor Replacement - Bank 2 Sensor 2