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 P2297: Performance During Decel Fuel Cut-Off (DFCO) Bank 1 Sensor 1
DTC P2298: Performance During Decel Fuel Cut-Off (DFCO) Bank 2 Sensor 1

### Typical Scan Tool Data

#### HO2S 1 or 2

Circuit | Short to Ground | Open | Short to Voltage
--- | --- | --- | ---
Operating Conditions: Engine operating in Closed Loop Parameter Normal Range: Fluctuates above and below 350-500 mV
Sensor Signal | 0-60 mV | 400-415 mV | 5000 mV
Low Reference | -- | 400-415 mV | 5000 mV

### Circuit Description

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 circuit. 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.

### Conditions for Running the DTCs

#### P2297, P2298

• | The ignition voltage is between 10-16 volts.

• | The engine is operating.

• | The front heated oxygen sensors are at operating temperature.

• | The internal ECM HO2S signal voltage is less than 4.81 volts.

• | A decel fuel cut-off has occurred 10 times with successful adjustments.

### Conditions for Setting the DTCs

#### P2297, P2298

The ECM detects that the internal HO2S signal voltage is more than 3.7 volts for more than 10 seconds or the ECM detects that the compensation factor of the HO2S is less than -25 percent or more than 30 percent of the expected value.

### Action Taken when the DTCs Set

DTCs P2297 and P2298 are type B DTCs.

### Conditions for Clearing the MIL/DTC

DTCs P2297 and P2298 are type B DTCs.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

Component 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

Control Module References

### Circuit/System Verification

1. Engine idling, observe the appropriate HO2S voltage parameter. The reading should fluctuate above and below the range of 350-550 mV.
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 HO2S sensor.
2. Ignition ON, verify that the HO2S parameter is between 350-500 mV.

⇒ | If less than 350 mV, test the signal circuit for a short to ground. If the circuit/connections test normal, replace the ECM.

⇒ | If greater than 500 mV, test the signal circuit for a short to voltage. If the circuit/connections test normal, replace the ECM.

3. Ignition OFF, test for 5 ohms or less between the low reference circuit of the HO2S sensor and a known ground.

⇒ | If greater than 5 ohms, test the low reference circuit for an open/high resistance. If the circuit/connections test normal, replace the ECM.

4. Install a 3A fusible link wire between the signal circuit and the low reference circuit of the HO2S sensor and verify the HO2S sensor parameter is less than 60 mV.

⇒ | If greater than 60 mV, test the signal circuit for an open/high resistance. If the circuit/connections test normal, replace the ECM.

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

### Repair Instructions

Perform the Diagnostic Repair Verification.

• | Heated Oxygen Sensor Replacement - Bank 1 Sensor 1

• | Heated Oxygen Sensor Replacement - Bank 2 Sensor 1

• | Engine Control Module Replacement for engine control module replacement, setup and programming.