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: Heater Control Circuit Bank 2 Sensor 1
DTC P0056: HO2S Heater Control Circuit 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, P0050, P0056 | 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: 0.5-2 A
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 sensor 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

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

• | The engine speed is more than 425 RPM.

• | The ignition is in the Crank or Run position.

• | DTC P0050 runs once per drive cycle when the above conditions are met.

#### P0056

• | Driver Output Command is ON.

• | The ignition 1 signal parameter is between 10-18 volts.

• | The engine speed is more than 425 RPM.

• | The ignition is in the Crank or Run position.

• | DTC P0056 runs once per drive cycle when the above conditions are met.

#### P0059 or P0060

• | The ECT sensor parameter minus the intake air temperature (IAT) sensor parameter is less than 8°C (14°F) at engine start-up

• | The ignition is OFF for more than 8 hours.

• | The engine coolant temperature (ECT) sensor parameter is between -30 and +45°C (-22 and +113°F) at engine start-up.

• | The ignition voltage is less than 18 volts.

• | Coolant temperature DTCs is inactive.

• | Ignition OFF timer DTCs is inactive.

• | IAT monitor DTCs is inactive.

• | DTC P0059 and P0060 run once per cold start when the above conditions are met.

#### 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, P1101, P1516, P2101, P2119, P2135, P2176 are not set.

• | The three-way catalytic monitor intrusive diagnostic tests is inactive.

• | The post oxygen sensor intrusive diagnostic tests is inactive.

• | The traction control, induction, fuel, idling, exhaust gas recirculation and engine No overspeed intrusive test is inactive.

• | The ignition 1 signal parameter is between 10-18 volts.

• | EGR valve, idling, fuel injectors and intake air output control is inactive.

• | The ECT sensor parameter is more than 60°C (140°F).

• | The MAF sensor parameter is between 5-45 g/s.

• | The engine running time parameter is more than 180 seconds.

• | The engine speed parameter is between 500-3,000 RPM.

• | The HO2S heater is not at the state of output control.

• | The HO2S Heater performance bank 2 sensor 2 resistance fault codes is inactive.

• | DTC P0141 runs the heater current test twice per drive cycle when the above conditions are met for 2 seconds, with a 120 second delay between each test.

#### 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, P1101, P1516, P2101, P2119, P2135, P2176 are not set.

• | The three-way catalytic monitor intrusive diagnostic tests is inactive.

• | The post oxygen sensor intrusive diagnostic tests is inactive.

• | The traction control, induction, fuel, idling, exhaust gas recirculation and engine No overspeed intrusive test is inactive.

• | EGR valve, idling, fuel injectors and intake air output control is inactive.

• | The ECT sensor parameter is more than 60°C (140°F)

• | The ignition 1 signal parameter is between 10-18 volts.

• | The MAF sensor parameter is between 5-45 g/s.

• | The engine running time parameter is more than 180 seconds.

• | The engine speed parameter is between 500-3,000 RPM.

• | The HO2S heater is not at the state of output control.

• | The HO2S Heater performance bank 2 sensor 1 resistance fault codes is inactive.

• | DTC P0135 runs the heater current test twice per drive cycle when the above conditions are met for 2 seconds, with a 120 second delay between each test.

### Conditions for Setting the DTC

#### P0050 or P0056

• | The control module detects that the affected HO2S heater low voltage control circuit is not within the specified range.

• | It occurs at least 20 times during the 25 tests.

• | DTC P0050 and P0056 are set when the above conditions are met.

#### P0059 or P0060

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

• | DTCs P0059 and P0060 are set when the above conditions are met.

#### P0161

• | The control module detects that the HO2S 2 heater current parameter is more than 3.125 amps or less than 0.25 amp.

• | DTC P0161 is set within 2 seconds when the above conditions are met during the heater current test. Two tests run per trip with 120 seconds delay between each test.

#### P0155

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

• | DTC P0155 runs the heater current test twice per drive cycle when the above conditions are met for 2 seconds, with a 120 second delay between each test.

### 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

• | Power Distribution Schematics

#### Connector End View Reference

• | Engine Control Module Connector End Views

• | Engine Controls Connector End Views

#### Description and Operation

Engine Control Module Description

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

• | Heated Oxygen Sensor Wiring Repairs

#### DTC Type Reference

Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

Scan Tool Data List

### 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 1 amp to above 2 amps.
2. With the engine running at operating temperature, observe the HO2S Heater parameter with scan tool and manipulate the related harness and connectors.

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

### Circuit/System Testing

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

1. Turn the ignition OFF, disconnect the harness connector at the appropriate HO2S sensor.
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 circuit terminal D and the terminals listed below the appropriate HO2S heater low control circuit.

• | B1S1 terminal E

• | B1S2 terminal C

• | B2S1 terminal E

• | B2S2 terminal C

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

4. With the 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 steady or flashing, test the HO2S heater low control circuit for a short to voltage or an open/high resistance. If the circuit test 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. When the resistance is less than 10 ohms, DTC may set.

• | Performing this test may set additional DTCs.

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

• | B1S1 terminal E

• | B1S2 terminal C

• | B2S1 terminal E

• | B2S2 terminal C

6. With the engine running, verify the appropriate scan tool heater parameter is less than 0.1.

⇒ | If more than the specified range, test the HO2S heater voltage supply and HO2S heater low control circuits for more than 1 ohm of resistance. If the circuit 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 Sensor Resistance Learn Reset Notice in the Preface section.

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 replacement, setup, and programming