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 P0030: O2 Sensor Heater Circuit Range/Performance (Bank 1 Sensor 1)
DTC P0036: O2 Sensor Heater Circuit Range/Performance (Bank 1 Sensor 2)
DTC P0050: O2 Sensor Heater Circuit Range/Performance (Bank 2 Sensor 1)
DTC P0056: O2 Sensor Heater Circuit Range/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 | Normal Range | Short to Ground | Open | Short to Voltage
--- | --- | --- | --- | ---
HO2S Heater Low Control | 1-2 A | 0 A | 0 A | 0 A
HO2S Heater Voltage Supply | 1-2 A | 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 a 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 commands the heater ON or OFF to maintain a specific HO2S operating temperature range.

The ECM monitors the voltage on the HO2S heater low control circuit for heater fault diagnosis. If the ECM detects that the HO2S heater low control circuit voltage is not within a specified range, DTC P0030 sets for HO2S bank 1 sensor 1, DTC P0036 sets for HO2S bank 1 sensor 2, DTC P0050 sets for HO2S bank 2 sensor 1 or DTC P0056 sets for HO2S bank 2 sensor 2.

### Conditions for Running the DTC

• | The Ignition 1 Signal parameter is between 9-18 volts.

• | The engine speed is more than 400 RPM.

• | DTCs P0030, P0036, P0050, P0056 run continuously when the above conditions are met.

### Conditions for Setting the DTC

• | The ECM detects that the affected HO2S heater low control circuit is not within a predetermined range.

• | DTCs P0030, P0036, P0050 and P0056 are set within 5 seconds when the above condition is met.

### Action Taken when the DTC Sets

DTCs P0030, P0036, P0050 or P0056 are type B DTCs.

### Conditions for Clearing the MIL/DTC

DTCs P0030, P0036, P0050 or P0056 are type B DTCs.

### Reference Information

#### Schematic Reference

Engine Controls Schematics .

#### Connector End View Reference

Component Connector End Views

#### Electrical Information Reference

• | Circuit Testing .

• | Testing for Intermittent Conditions and Poor Connections .

• | Wiring Repairs .

#### Scan Tool Reference

Control Module References

### Circuit/System Verification

• | Allow the engine to reach operating temperature. Using a scan tool, engine running observe the HO2S Heater parameter. The parameter should indicate active.

• | With the engine running observe the HO2S Heater parameter and manipulate the related wiring and connectors.

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

### 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 B+ circuit terminal and known ground.

⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, replace the HO2S.

3. Ignition OFF, verify that the test lamp is off between the heater low control circuit terminal of the appropriate HO2S and B+.

⇒ | If the test lamp illuminates, test the low control circuit for a short to ground open/high resistance.

4. Connect a test lamp between the heater low control circuit terminal of the appropriate HO2S and the B+ circuit.
5. Ignition On, engine running, the test lamp should be flash or remain illuminated.

⇒ | If the test lamp is not illuminated, test the low control circuit for a short to voltage or open/high resistance. If the circuit tests normal, replace the ECM.

6. Ignition OFF, install a 30-A fusible link wire between the B+ circuit terminal and the heater low control circuit of the appropriate HO2S.
7. Ignition ON, engine running Using scan tool to observe that the appropriate HO2S heater parameter indicates active.

⇒ | If the scan tool does not indicate active, test the heater B+ circuit and the low control circuit for resistance greater than 3 ohms. If the circuit tests normal, replace the control module.

8. If all circuits test normal, test or replace the appropriate HO2S.

### 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

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