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 1 Heater Control | P0030 | P0030 | P0030 | --
HO2S 2 Heater Control | P0036 | P0036 | P0036 | --

### Circuit 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

#### P0030

• | DTCs P0107, P0108, P0117, P0118 are not set.

• | The engine has been operating for 3 minutes.

• | The DTC runs continuously when the above conditions are met.

#### P0036

• | The ignition 1 voltage is greater than 10 volts.

• | The engine has been operating for 30 seconds.

• | The DTCs run continuously when the above conditions.

### Conditions for Setting the DTC

#### P0030

The ECM detects that the HO2S 1 heater current is less than 0.1 amp for 3 seconds.

#### P0036

The ECM detects that the HO2S 2 heater current is less than 0.1 amp for 13 seconds.

### Action Taken When the DTC Sets

DTCs P0030 and P0036 are Type B DTCs.

### Conditions for Clearing the MIL/DTC

DTCs 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 of the appropriate heated oxygen sensor (HO2S).

Important: The test lamp is used to load the circuit and may not illuminate.

2. Connect a test lamp between the ignition 1 voltage circuit of the HO2S heater and ground.
3. Ignition ON, test for less than 0.1 volt between the ignition 1 voltage circuit of the HO2S heater at the test lamp probe and B+.

⇒ | If greater than 0.1 volt, repair the ignition 1 voltage circuit of the HO2S heater for a short to ground or an open/high resistance.

4. Ignition OFF, connect a test lamp between the control circuit of the HO2S heater and B+.

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

5. Ignition ON, test for less than 0.3 volt between the control circuit of the HO2S heater at the test lamp probe and ground.

⇒ | If greater than 0.3 volt, test the control circuit of the HO2S heater for a short to voltage or an open/high resistance. 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 of the heated oxygen sensor (HO2S).
2. Test the HO2S heater resistance for 3-35 ohms.

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

### 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 engine control module replacement, setup, and programming