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 Bank 1 Sensor 1
DTC P0031: HO2S Heater Control Circuit Low Voltage Bank 1 Sensor 1
DTC P0032: HO2S Heater Control Circuit High Voltage Bank 1 Sensor 1
DTC P0036: Heater Control Circuit Bank 1 Sensor 2
DTC P0037: HO2S Heater Control Circuit Low Voltage Bank 1 Sensor 2
DTC P0038: HO2S Heater Control Circuit High Voltage Bank 1 Sensor 2
DTC P0050: HO2S Heater Control Circuit Bank 2 Sensor 1
DTC P0051: HO2S Heater Control Circuit Low Voltage Bank 2 Sensor 1
DTC P0052: HO2S Heater Control Circuit High Voltage Bank 2 Sensor 1
DTC P0056: HO2S Heater Control Circuit Bank 2 Sensor 2
DTC P0057: HO2S Heater Control Circuit Low Voltage Bank 2 Sensor 2
DTC P0058: HO2S Heater Control Circuit High Voltage Bank 2 Sensor 2

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Ignition Voltage | P0030, P0036, P0050, P0056 | P0030, P0036, P0050, P0056 | -- | P0135, P0141, P0155, P0161
HO2S Heater Control Sensor 1 | P0031, P0051 | P0030, P0050, P0134, P0154 | P0032, P0052 | P0135, P0141, P0155, P0161
HO2S Heater Control Sensor 2 | P0037, P0057 | P0036, P0056, P0140, P0160 | P0038, P0058 | P0135, P0141, P0155, P0161

### Circuit Description

The heated oxygen sensor (HO2S) heater reduces the time required for the oxygen sensor to reach operating temperature and maintains the operating temperature during extended idle periods. When the ignition is turned to the ON position, ignition voltage is supplied directly to the sensor heater. The engine control module (ECM) controls the heater operation by first modulating the control circuit to ground when the sensors are cold. This prevents the possibility of thermal shock to the sensor, from condensation build-up on the sensor, by controlling the sensors rate of heating. After a predetermined amount of time, the ECM commands the heaters ON continuously. Once the sensor reaches operating temperature, the ECM may modulate the heater control circuit to ground, to maintain a desired temperature.

The ECM controls the heater by grounding the control circuit with a solid state device called a driver. The driver is equipped with a feedback circuit that is pulled-up to voltage. The ECM can determine if the control circuit is open, shorted to ground, or shorted to a voltage by monitoring the feedback voltage.

The HO2S utilizes the following circuits:

• | A signal circuit

• | A low reference circuit

• | An ignition voltage circuit

• | A heater control circuit

### Conditions for Running the DTC

#### P0030, P0031, P0032, P0050, P0051, P0052

• | The ignition voltage is between 10-18 volts.

• | The engine speed is greater than 80 RPM.

• | The HO2S heater is commanded ON and OFF at least once during the ignition cycle.

• | The DTCs run continuously when the above conditions are met.

#### P0036, P0037, P0038, P0056, P0057, P0058

• | The ignition voltage is between 10-18 volts.

• | The engine speed is greater than 80 RPM.

• | The HO2S heater is commanded ON and OFF at least once during the ignition cycle.

• | The HO2S 2 is at operating temperature.

• | The DTCs run continuously when the above conditions are met for greater than 500 ms.

### Conditions for Setting the DTC

#### P0030, P0036, P0050, and P0056

The ECM detects an open in the heater circuits of the HO2S when the heater is commanded OFF. The condition exists for greater than 4 seconds or a cumulative of 30 seconds.

#### P0031, P0037, P0051, and P0057

The ECM detects a ground in the heater circuits of the HO2S when the heater is commanded OFF. The condition exists for greater than 4 seconds or a cumulative of 30 seconds.

#### P0032, P0038, P0052, and P0058

The ECM detects a short to voltage in the heater circuits of the HO2S when the heater is commanded ON. The condition exists for greater than 4 seconds or a cumulative of 30 seconds.

### Action Taken When the DTC Sets

DTCs P0030, P0031, P0032, P0036, P0037, P0038, P0050, P0051, P0052, P0056, P0057, and P0058 are Type B DTCs.

### Conditions for Clearing the MIL/DTC

DTCs P0030, P0031, P0032, P0036, P0037, P0038, P0050, P0051, P0052, P0056, P0057, and P0058 are Type B DTCs.

### Diagnostic Aids

• | If the condition is intermittent, move the related harnesses and connectors, with the engine operating, while monitoring the scan tool circuit test status parameters for the component. The circuit test status parameters change from OK or Not Run to Fault if there is a condition with the circuit or a connection.

• | An open fuse in the HO2S heater circuit may be caused by the heater element in one of the sensors. The condition may not be present until the sensor operates for a period of time. If no fault is present in the heater circuit, monitor the amperage of each heater using the DMM to determine if one of the heater elements is the cause of the open fuse. Inspect the sensor pigtail or the harness for contacting the exhaust system.

### 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

#### DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

#### Scan Tool Reference

Control Module References for scan tool information

### Circuit/System Verification

1. Engine idling at operating temperature for at least 30 seconds. Observe the DTC information. DTC P0030, P0031, P0032, P0036, P0037, P0038, P0050, P0051, P0052, P0056, P0057, or P0058 should not set.
2. Observe the appropriate scan tool HO2S Heater Circuit Test Status parameter. The parameter should display OK or Not Run.
3. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

### Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the appropriate heated oxygen sensor (HO2S).
2. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal C and ground.

Note: The ignition 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 circuit.

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

3. Connect a test lamp between the heater control circuit terminal D and B+. The test lamp should not illuminate.

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

Note: The control circuit for the HO2S heater is pulled-up to voltage within the ECM, 2.0-3.0 V on the control circuit is normal.

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

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

5. Ignition ON, test for 2.0-3.0 V between the control circuit terminal D and ground.

⇒ | If not within the specified range, test the control circuit for a short to voltage. If the circuit/connections test normal, replace the ECM.

6. If all circuits/connections test normal, test or replace the appropriate HO2S.

### Component Testing

1. Ignition OFF, disconnect the harness connector at the heated oxygen sensor (HO2S) sensor.
2. Test the HO2S heater resistance for 3-35 Ω.

⇒ | If not within the specified range, replace the HO2S sensor.

### Repair Instructions

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 ECM replacement, setup, and programming