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: O2 Sensor Heater Circuit Range/Performance (Bank 1 Sensor 1)
DTC P0141: O2 Sensor Heater Circuit Range/Performance (Bank 1 Sensor 2)
DTC P0155: O2 Sensor Heater Circuit Range/Performance (Bank 2 Sensor 1)
DTC P0161: O2 Sensor Heater Circuit Range/Performance (Bank 2 Sensor 2)

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Ignition Voltage Supply - HO2S Bank 1 and 2 Sensor 1 | P0030, P0031, P0050, P0051 | P0135, P0141 | -- | --
Ignition Voltage Supply - HO2S Bank 1 and 2 Sensor 2 | P0036, P0037, P0056, P0057 | P0135 | -- | --
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.

### Conditions for Running the DTCs

#### P0135 or P0155

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

• | DTC P0130, P0131, P0132, P0134, P0150, P0151, P0152, or P0154 is not set.

• | The engine is operating.

• | The ignition voltage is 10-18 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 524°C (975°F).

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

• | The HO2S 1 is at operating temperature for greater than 10 seconds.

• | The internal HO2S 1 resistance is less than 10,000 Ω.

• | The DTCs 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 P0030, P0031, P0032, P0050, P0051, and P0052 must run and pass.

• | DTCs P0130, P0131, P0132, P0134, P0150, P0151, P0152, or P0154 are not set.

• | The engine is operating.

• | The ignition voltage is 10-18 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 0 seconds.

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

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

• | The internal HO2S 2 resistance is less than 10,000 Ω.

• | The HO2S 2 heater is enabled for greater than 120 seconds.

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

### Conditions for Setting the DTCs

The ECM detects that the internal resistance of an HO2S 1 or HO2S 2 heater is not within the expected range.

### 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

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

Note: 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. 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 you observed from the Freeze Frame/Failure Records data.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the appropriate HO2S.
2. Ignition ON, test for B+ on the HO2S ignition circuit terminal 1 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 2 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.

⇒ | If the test lamp is always OFF, test the control circuit terminal 2 for an open/high resistance. If the circuit/connections test normal, replace the ECM.

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

5. Ignition ON, test for 2.0-3.0 V between the control circuit terminal 2 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 at the heated oxygen sensor (HO2S) sensor.
2. Test for 5-25 Ω between the control terminal 2 and the ignition terminal 1 of the heated oxygen sensor (HO2S) sensor.

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

### Repair Instructions

Perform the Diagnostic Repair Verification .

• | 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

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