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 heated oxygen sensor (HO2S) heater reduces the time required for the oxygen sensor to reach operating temperature and maintains the operating temperature during extended idle periods. When the ignition is turned to the ON position, ignition voltage is supplied directly to the sensor heater. The engine control module (ECM) controls the heater operation by first modulating the control circuit to ground when the sensors are cold. This prevents the possibility of thermal shock to the sensor, from condensation build-up on the sensor, by controlling the sensors rate of heating. After a predetermined amount of time, the ECM commands the heaters ON continuously. Once the sensor reaches operating temperature, the ECM may modulate the heater control circuit to ground, to maintain a desired temperature.

### 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 11-18 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 above -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 greater 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

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 for scan tool information

### 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. 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. Ignition OFF, disconnect the harness connector at the appropriate HO2S.
2. Ignition ON, load test for B+ between the appropriate ignition voltage circuit terminal listed below and ground.

• | Bank 1 or 2 Sensor 1 Terminal 2

• | Bank 1 or 2 Sensor 2 Terminal 1

⇒ | If less than the specified range, repair the ignition voltage circuit for a short to ground or open/high resistance.

3. Ignition OFF, connect a test lamp between the appropriate heater control circuit terminal listed below and B+. The test lamp should not illuminate.

• | Bank 1 or 2 Sensor 1 Terminal 5

• | Bank 1 or 2 Sensor 2 Terminal 2

⇒ | If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the ECM.

4. Ignition ON, load test for less than 0.3 volt between the appropriate heater control circuit terminal listed below and ground.

• | Bank 1 or 2 Sensor 1 Terminal 5

• | Bank 1 or 2 Sensor 2 Terminal 2

⇒ | If greater than the specified range, test the control circuit 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 at the appropriate HO2S.
2. Test for 3-35 ohms between the HO2S heater terminals listed below.

• | Bank 1 or 2 Sensor 1 Terminals 2 and 5

• | Bank 1 or 2 Sensor 2 Terminals 1 and 2

⇒ | If not within the specified range, replace the HO2S sensor.

### 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.