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 provide an overview of each diagnostic category.

### DTC Descriptors

DTC P2196: HO2S Signal Biased Rich Bank 1 Sensor 1
DTC P2198: HO2S Signal Biased Rich 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. 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 greater 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. If the ECM detects that the HO2S signal voltage is low, this DTC sets.

### Conditions for Running the DTC

• | The engine is operating.

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

• | The engine is running in closed loop.

• | DTCs P2195 and P2197 run continuously once the above conditions are met.

### Conditions for Setting the DTC

The ECM detects that the front HO2S is operating too rich while the rear HO2S is operating too lean and the ECM detects that the fuel trim is at minimum control.

OR

The ECM detects that the rear HO2S is operating too lean while the ECM is commanding a rich air/fuel mixture.

### Action Taken When the DTC Sets

DTCs P2196 and P2198 are Type B DTCs.

### Conditions for Clearing the MIL/DTC

DTCs P2196 and P2198 are Type B DTCs.

### 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

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

1. Operate the vehicle within the conditions for running the DTC. DTCs P2196 or P2198 should not set.
2. 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.

### Circuit/System Testing

1. Verify that none of the following conditions exist:

• | Inspect the appropriate HO2S 1 and HO2S 2 for being secure

• | Damaged wiring between either HO2S and the ECM

• | Leaking fuel injectors--Refer to Fuel Injector Balance Test with Special Tool or Fuel Injector Balance Test with Tech 2

• | High fuel system pressure--Refer to Fuel System Diagnosis

• | Fuel that is contaminated-- Alcohol/Contaminants-in-Fuel Diagnosis

• | Contaminated HO2S-Silicon

⇒ | If you find any of the above conditions, repair as necessary.

2. Ignition OFF, disconnect the harness connector at the appropriate HO2S 2.
3. Ignition ON, verify the scan tool HO2S 2 voltage parameter is between 350-550 mV

⇒ | If greater than the specified range, test the HO2S 2 high signal circuit for a short to voltage. If the circuit/connections test normal, replace the ECM.

4. Connect the harness connector at the HO2S 2.
5. Engine idling, raise the engine speed above 1,200 RPM for 30 seconds. Verify the scan tool HO2S 2 voltage parameter is less than 1,000 mV.

⇒ | If greater than the specified range, replace the HO2S 2.

6. Engine idling, move the HO2S 1 and HO2S 2 harnesses between the HO2S harness connector and the ECM. Observe the scan tool HO2S 1 lambda parameter, and the HO2S 2 voltage parameter. Verify the parameters do not change abruptly.

⇒ | If the parameter changes abruptly, repair the harness/connections as necessary.

7. If all circuits/connections test normal, replace the appropriate HO2S 1.

### Component Testing

1. Ignition OFF, disconnect the harness connector of the appropriate HO2S.
2. Test the HO2S heater resistance for 3-35 ohms.

⇒ | If the resistance is out of the specified range, replace the HO2S.

### Repair Instructions

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 engine control module replacement, setup, and programming.