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 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 Voltage Supply - Primary HO2S | P0030, P0031, P0050, P0051 | P0010, P0013, P0023, P0030, P0031, P0050, P0051, P0134, P0135, P0154, P0155, P0458, P2088 | -- | --
Ignition Voltage Supply - Secondary HO2S | P0036, P0037, P0056, P0057 | P0036, P0037, P0056, P0057, P0140, P0160, P0645, P0646, P0691, P0693 | -- | --
HO2S Bank 1 Sensor 1 Heater Control | P0031 | P0030, P0134 | P0032 | P0135
HO2S Bank 1 Sensor 2 Heater Control | P0037 | P0036, P0140 | P0038 | P0141
HO2S Bank 2 Sensor 1 Heater Control | P0051 | P0050, P0154 | P0052 | P0155
HO2S Bank 2 Sensor 2 Heater Control | P0057 | P0056, P0160 | P0058 | P0161

### 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 sensor's 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. The ECM controls the heater by grounding the control circuit with a solid state device called a driver. The driver is equipped with a feedback circuit that is pulled up to voltage. The ECM can determine if the control circuit is open, shorted to ground, or shorted to a voltage by monitoring the feedback voltage.

### Conditions for Running the DTC

#### P0135 or P0155

• | Before the ECM can report DTC P0135 or P0155 failed, P0030, P0031, P0032, P0050, P0051, and P0052 must run and pass.

• | DTCs P0131, P0132, P0134, P0151, P0152, and P0154 are not set.

• | The engine is operating.

• | The ignition voltage is 10.5-18.1 volts.

• | The intake air temperature (IAT) is greater than -30°C (-22°F).

• | After the previous ignition cycle the engine OFF time was greater than 2 minutes.

• | The calculated exhaust temperature is less than 500°C (932°F).

• | The engine is not in decel fuel cut-off (DFCO).

• | The HO2S is at operating temperature for greater than 10 seconds.

• | The internal HO2S resistance is less than 10,000 ohms.

• | DTCs P0135 and P0155 run continuously once the above conditions are met for approximately 100 seconds.

#### P0141 or P0161

• | Before the ECM can report DTC 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 voltage is 10.5-18.1 volts.

• | The intake air temperature (IAT) is greater than -30°C (-22°F).

• | After the previous ignition cycle the engine OFF time was greater than 2 minutes.

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

• | The engine is not in decel fuel cut-off (DFCO).

• | The internal HO2S resistance is less than 10,000 ohms.

• | DTCs P0141 and P0161 run continuously once the above conditions are met for approximately 100 seconds.

### Conditions for Setting the DTC

The ECM detects that the internal resistance of a primary or secondary HO2S heater is not within the expected range for more than 4 seconds or for a cumulative of 50 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.

### 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. With the engine at normal operating temperature, operate the engine above 1,200 RPM for 2 minutes and then allow the engine to idle. 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, test for B+ on the HO2S ignition voltage circuit terminal C of the HO2S harness connector.

⇒ | If less than the specified value, repair the ignition voltage circuit of the HO2S heater for a short to ground or an open/high resistance.

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

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

4. Idle the engine, and verify the test lamp illuminates or flashes with bright intensity.

⇒ | If the test lamp is always OFF, test the control circuit for an open/high resistance. If the circuit/connections test normal, replace the ECM.

Important: The control circuit for the HO2S heater is pulled-up to voltage within the ECM, 2.0-3.0 volts on the control circuit is normal.

5. Ignition ON, test for 2.0-3.0 volts between the control circuit terminal D and ground.

⇒ | If not within the specified range, test the control circuit for a short to voltage. If the circuit/connections test normal, replace the ECM.

6. If all circuits/connections 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