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 provide an overview of each diagnostic category.

### DTC Descriptors

DTC P0030: HO2S Heater Performance Sensor 1
DTC P0036: HO2S Heater Performance Sensor 2

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Ignition 1 Voltage | P0030, P0036 | P0030, P0036 | -- | --
HO2S Heater Control Sensor 1 | P0030 | P0030 | P0030 | --
HO2S Heater Control Sensor 2 | P0036 | P0036 | P0036 | --

### Circuit/System Description

The 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 the ignition 1 voltage circuit through a fuse. Ground is provided to the heater on the low control circuit by a low side driver within the control module. The control module monitors the current draw of the heater to determine if a failure is present.

The HO2S utilizes the following circuits:

• | A signal circuit

• | A low reference circuit

• | An ignition 1 voltage circuit

• | A heater control circuit

### Conditions for Running the DTC

• | The HO2S heater pulse width modulation (PWM) is at 98 percent after cranking.

• | The airflow is between 6 kg/h and 40 kg/h.

• | The ignition 1 voltage is between 11.07-15.47 volts.

• | The predicted catalyst temperature is higher than 300°C (572°F).

• | DTC P0030 and P0036 runs continuously once the above conditions are met.

### Conditions for Setting the DTC

The HO2S heater resistance is less than 3 ohms or greater than 35 ohms.

### Action Taken When the DTC Sets

DTC P0030 and P0036 are Type B DTCs.

### Conditions for Clearing the MIL/DTC

DTC P0030 and P0036 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 30 seconds and then allow the engine to idle. DTC P0030 or P0036 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 Data List.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the appropriate H02S.
2. Ignition ON, verify that a test lamp illuminates between the ignition 1 voltage circuit and ground.

Important: The ignition 1 voltage circuit supplies voltage to other components. Make sure you test all circuits for a short to ground or test all components for being shorted that share the ignition 1 voltage circuit.

⇒ | If the test lamp does not illuminate, test the ignition 1 voltage circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition 1 voltage circuit fuse is open, test all components connected to the ignition 1 voltage circuit and replace as necessary.

3. Ignition OFF, connect a test lamp between the control circuit and B+. The test lamp should not illuminate.

Important: The control circuit for the HO2S heater is pulled-up to voltage within the ECM, 3.5 to 4.5 volts on the control circuit is normal.

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

4. Start and idle the engine, and verify the test lamp illuminates or flashes.

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

5. If all circuits/connections test normal, test or replace the H02S sensor.

### Component Testing

1. Ignition OFF, disconnect the harness connector of the HO2S sensor.
2. Test the HO2S heater resistance for 3-35 ohms.

⇒ | If the resistance is out of the specified range, replace the HO2S sensor.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Heated Oxygen Sensor 1 Replacement

• | Heated Oxygen Sensor 2 Replacement

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