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 P0050: HO2S Heater Control Bank 2 Sensor 1
DTC P0056: HO2S Heater Control Bank 2 Sensor 2
DTC P0059: HO2S Heater Resistance Bank 2 Sensor 1
DTC P0060: HO2S Heater Resistance Bank 2 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 | High Resistance | Open | Short to Voltage | Signal Performance
--- | --- | --- | --- | --- | ---
HO2S Heater Voltage Supply | Opens fuse | P0030, P0036, P0050, P0053, P0054, P0056, P0059, P0060, P0135, P0141, P0155, P0161 | P0030, P0036, P0050, P0056, P0135, P0141, P0155, P0161 | -- | P0135, P0141, P0155, P0161
HO2S Heater Low Control | P0030, P0036 | P0030, P0036, P0050, P0053, P0054, P0056, P0059, P0060, P0135, P0141, P0155, P0161 | P0030, P0036, P0050, P0056, P0135, P0141, P0155, P0161 | P0030, P0036, P0050, P0056, P0135, P0141, P0155, P0161 | P0135, P0141, P0155, P0161

### Typical Scan Tool Data

#### HO2S Heater

Circuit | Short to Ground | Open | Short to Voltage
--- | --- | --- | ---
Parameter Normal Range: 200-800 mV
HO2S Heater Low Control | 0 A | 0 A | 0 A
HO2S Heater Voltage Supply | 0 A | 0 A | 1-2 A

### Circuit/System Description

Heated oxygen sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content in the exhaust stream. The HO2S must reach operating temperature to provide an accurate voltage signal. A heating element inside the HO2S minimizes the time required for the sensors to reach operating temperature. Voltage is provided to the heater by an ignition voltage circuit through a fuse. With the engine running, ground is provided to the heater by the HO2S heater low control circuit through a low side driver within the engine control module (ECM). The ECM uses pulse width modulation (PWM) to control the HO2S heater operation to maintain a specific HO2S operating temperature range.

### Conditions for Running the DTC

#### P0050 or P0056

• | The ignition 1 signal parameter is between 11-18 volts.

• | The engine speed is more than 400 RPM.

• | DTCs 0050 or P0056 run once per drive cycle when the above conditions are met.

#### P0059 or P0060

• | DTCs P0112, P0113, P0117, P0118 are not set.

• | The engine is started.

• | The ignition voltage is less than 18 volts.

• | The ignition is OFF form more than 10 hours.

• | The Engine Coolant Temperature (ECT) Sensor parameter is between -30 and +45°C (-22 and +113°F) at engine start-up.

• | The Engine Coolant Temperature (ECT) Sensor parameter minus the Intake Air Temperature (IAT) Sensor parameter is less than 8°C (14°F) at engine start-up.

• | DTCs P0059 or P0060 run once per drive cycle when the above conditions are met.

#### P0155

• | DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0455, P0496, P1516, P2101, P2119, P2135, P2176 are not set.

• | The ECT Sensor parameter is more than 50°C (122°F).

• | The Ignition 1 Signal parameter is between 10-18 volts.

• | The MAF Sensor parameter is between 3-40 g/s.

• | The Engine Run Time parameter is more than 300 seconds.

• | The Engine Speed parameter is between 500-3,000 RPM.

• | DTC P0155 runs the heater current test once per drive cycle when the above conditions are met for 120 seconds.

#### P0161

• | DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0455, P0496, P1516, P2101, P2119, P2135, P2176 are not set.

• | The ECT Sensor parameter is more than 50°C (122°F).

• | The Ignition 1 Signal parameter is between 10-18 volts.

• | The MAF Sensor parameter is between 3-40 g/s.

• | The Engine Run Time parameter is more than 300 seconds.

• | The Engine Speed parameter is between 500-3,000 RPM.

• | DTC P0161 runs the heater current test twice per drive cycle when the above conditions are met for 120 seconds.

### Conditions for Setting the DTC

#### P0050 or P0056

• | The ECM detects that the affected HO2S heater low control circuit is not within a specified range at engine start-up.

• | DTCs P0050, and P0056 set within 1 second when the above condition is met.

#### P0059

• | The ECM detects that the affected HO2S heater low control circuit is not within a specified resistance range at engine start-up.

• | DTCs P0059 sets within 1 second when the above condition is met.

#### P0060

• | The ECM detects that the affected HO2S heater low control circuit is not within a specified resistance range at engine start-up.

• | DTCs P0060 sets within 1 second when the above condition is met.

#### P0155

• | The ECM detects that the HO2S 1 heater current parameter is more than 3.125 amps or less than 0.25 amp.

• | DTC P0155 sets within 120 seconds during the heater current test when the above condition is met.

#### P0161

• | The ECM detects that the HO2S 2 heater current parameter is more than 2.875 amps or less than 0.25 amp.

• | DTC P0161 sets within 120 seconds during the heater current test when the above condition is met.

### Action Taken When the DTC Sets

DTCs P0050, P0056, P0059, P0060, P0155, and P0161 are Type B DTCs.

### Conditions for Clearing the MIL/DTC

DTCs P0050, P0056, P0059, P0060, 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

• | Heated Oxygen Sensor Wiring 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

1. Allow the engine to reach operating temperature. With the engine running, observe the HO2S Heater parameter with a scan tool. The value should vary from below 2A to above 1A.
2. With the engine running at operating temperature, observe the HO2S Heater parameter with a scan tool and manipulate the related wiring and connectors.

⇒ | If manipulation does affect the parameter then repair the harness or connector.

3. 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

Important: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.

1. Ignition OFF, disconnect the harness connector at the appropriate HO2S.
2. Ignition ON, verify that a test lamp illuminates between the appropriate HO2S heater voltage supply circuit terminal D and ground.

⇒ | If the test lamp does not illuminate, test the HO2S heater voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal and the HO2S heater voltage supply circuit fuse is open, test all components connected to the fuse and replace as necessary.

3. Ignition ON, verify that a test lamp does not illuminate between the appropriate HO2S heater voltage supply control circuit terminal D and the appropriate HO2S heater low control circuit terminal listed below:

• | B2S1 terminal C

• | B2S2 terminal C

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

4. Engine running, leave the test lamp connected from the previous step. The lamp should flash or be ON steady.

⇒ | If the test lamp is not ON steady or flashing, test the HO2S heater low control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.

Important:

• | The output driver should detect a short to voltage and turn OFF. If a resistance fault is present the driver will remain ON and the scan tool will display more than 0.0 amp. Less than 10 ohms may set a DTC.

• | Performing this test may set additional DTCs.

5. Ignition OFF, install a 30A fused jumper wire between the appropriate HO2S heater voltage supply circuit terminal D and the appropriate HO2S heater low control circuit terminal listed below:

• | B2S1 terminal C

• | B2S2 terminal C

6. Engine running, verify the appropriate scan tool HO2S Heater parameter is less than 0.1 amp.

⇒ | If more than the specified range, test the HO2S heater voltage supply and HO2S heater low control circuits for more than 1 ohm. If the circuits test normal, replace the ECM.

7. If the ECM and all circuits test normal, replace the appropriate HO2S.

### Repair Instructions

Notice: Refer to Heated Oxygen and Oxygen Sensor Notice in the Preface section.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Heated Oxygen Sensor Replacement - Bank 2 Sensor 1

• | Heated Oxygen Sensor Replacement - Bank 2 Sensor 2

• | Control Module References for ECM replacement, setup, and programming