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 : HO2S Heater Control Circuit Sensor 1
DTC P0031 : HO2S Heater Control Circuit Low Voltage Sensor 1
DTC P0032 : HO2S Heater Control Circuit High Voltage Sensor 1
DTC P0135 : HO2S Heater Performance Sensor 1

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
HO2S 1 Heater Voltage Supply | P0031, P0130 | P0030, P0130, P0135 | -- | --
HO2S 1 Heater Low Control | P0031, P0130 | P0031, P0135 | P0032 | --
HO2S 1 Signal | P0131 | P0134 | P0132 | P0133, P0134, P2297, P2A00
HO2S 1 Voltage Reference | Opens Fuse | P0134 | -- | --

### Circuit/System Description

Heated oxygen sensors (HO2S) are used for fuel control and post-catalyst monitoring. The HO2S 2 compares the oxygen content of the surrounding air with the oxygen content in the exhaust stream. The HO2S 2 must reach operating temperature to provide an accurate voltage signal. A heating element inside the HO2S 2 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 2 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 2 heater operation to maintain a specific HO2S 2 operating temperature range.

### Conditions for Running the DTC

#### P0030, P0031, P0032

• | The ignition is ON.

• | The Ignition 1 Signal parameter is more than 9 volts.

#### P0135

• | DTCs P0030, P0031, P0032, P0068, P0101, P0102, P0103, P0130, P0131, P0132, P0134, P1101 are not set.

• | The engine is running.

• | The ignition 1 signal parameter is more than 9 volts.

### Conditions for Setting the DTC

#### P0030, P0031, P0032

The ECM detects that the difference between the predicted voltage and the actual voltage exceeds a calibrated limit.

#### P0135

The ECM detects that the sensor heater resistance is more than 1,200 ohms.

### Action Taken When the DTC Sets

DTCs P0030, P0031, P0032, P0135 are Type B DTCs.

### Conditions for Clearing the DTC

DTCs P0030, P0031, P0032, P0135 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

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

• | Heated Oxygen Sensor 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. Clear the DTCs with a scan tool.
2. Operate the vehicle within the conditions for running and setting the DTC. The DTC should not set.

### Circuit/System Testing

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

1. Ignition OFF, disconnect the harness connector at the HO2S 1.
2. Ignition ON, verify that a test lamp illuminates between the HO2S 1 heater voltage supply circuit terminal 3 and ground.

⇒ | If the test lamp does not illuminate, test the HO2S 1 heater voltage supply circuit for a short to ground or an open/high resistance. If the circuit tests normal and its 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 HO2S 1 heater low control circuit terminal 1 and the HO2S 1 heater voltage supply circuit terminal 3.

⇒ | If the test lamp illuminates, test the HO2S 1 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 1 heater low control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.

5. If the ECM and all circuits test normal, replace the HO2S 1.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Heated Oxygen Sensor 1 Replacement

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