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 P0135: HO2S Heater Performance Bank 1 Sensor 1
DTC P0141: HO2S Heater Performance Bank 1 Sensor 2
DTC P0155: HO2S Heater Performance Bank 2 Sensor 1
DTC P0161: HO2S Heater Performance Bank 2 Sensor 2

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Ignition 1 Voltage | P0135, P0141 | P0135, P0141 | -- | --
HO2S 1 Heater Control | P0135 | P0135 | P0135 | --
HO2S 2 Heater Control | P0141 | P0141 | P0141 | --

### 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 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. If the ECM detects that the HO2S signal voltage is low, this DTC sets.

### Conditions for Running the DTC

• | Before the ECM can report DTCs P0141 or P0161 failed, DTCs P0036, P0037, P0038, P0056, P0057, and P0058 must run and pass.

• | DTCs P0137, P0138, P0140, P0157, P0158, or P0160 are not set.

• | The engine is operating.

• | The ignition 1 voltage is between 10.5-18 volts.

• | The ECM internal sensing element resistance is valid.

• | The fuel system is not in a decel fuel shut-off.

• | The intake air temperature (IAT) is more than -10°C (+14°F).

• | If the engine is operating and then the ignition is turned OFF, the engine must be OFF for at least 2 minutes before the next start-up for the diagnostic to run.

• | The calculated exhaust temperature is between 360-500°C (680-932°F).

• | DTCs P0141 and P0161 run continuously once the above conditions are met.

### Conditions for Setting the DTC

The ECM detects that the HO2S internal resistance is not within the expected range for more than 10 seconds.

### Action Taken When the DTC Sets

DTCs P0135, P0141, P0155, and P0161 are Type B DTCs.

### Conditions for Clearing the MIL/DTC

DTCs P0135, P0141, P0155, and P0161 are Type B DTCs.

### Diagnostic Aids

The front wide band sensors do not toggle or switch like a switching HO2S. The front HO2S signals will be relatively stable for an idling 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

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 P0135, P0141, P0155, or P0161 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 List.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector of the appropriate HO2S.
2. Ignition ON, load test for battery voltage on the ignition voltage circuit of the HO2S heater.

⇒ | If less than B+, repair the short to ground or open/high resistance on the ignition voltage circuit of the HO2S heater .

3. Ignition OFF, connect a test lamp between the control circuit of the HO2S heater and B+.

⇒ | If test lamp illuminates, test the control circuit of the HO2S heater for a short to ground. If the circuit tests normal, replace the ECM.

4. Ignition ON, test for less than 0.3 volt between the control circuit of the HO2S heater at the test lamp probe and ground.

⇒ | If greater than the specified range, test the control circuit of the HO2S heater for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.

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

### 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.