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 Descriptor

DTC P0036 00: HO2S Heater Control Circuit Sensor 2
DTC P0037 00: HO2S Heater Control Low Voltage Sensor 2
DTC P0038 00: HO2S Heater Control Circuit High Voltage Sensor 2
DTC P0141 00: HO2S Heater Performance Sensor 2

### Diagnostic Fault Information

Circuit | Short to Ground | Open | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
HO2S 2 Heater Voltage Supply | Open fuse | P0036 00, P0037 00, P0141 00 | -- | P0141 00
HO2S 2 Heater Low Control | P0036 00, P0037 00 | P0036 00, P0037 00, P0141 00 | P0036 00, P0038 00, P0141 00 | P0141 00
HO2S 2 Signal | P0137 00 | P0140 00 | P0138 00 | P0139 00, P0140 00, P2A01 00, P2270 00, P2271 00
HO2S 2 Voltage Reference | Open fuse | P0140 00 | -- | --

### Circuit/System Description

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

#### P0036 00

The ECM monitors the voltage on the heated oxygen sensor (HO2S) 2 heater low control circuit for heater fault diagnosis. If the ECM detects that the heated oxygen sensor (HO2S) 2 heater low control circuit voltage is not within a specified range, DTC P0036 00 sets.

#### P0037 00

The ECM monitors the voltage on the heated oxygen sensor (HO2S) 2 heater low control circuit for heater fault diagnosis. If the ECM detects that theheated oxygen sensor (HO2S) 2 heater low control circuit voltage is below a specified range, DTC P0037 00 sets.

#### P0038 00

The ECM monitors the voltage on the heated oxygen sensor (HO2S) 2 heater low control circuit for heater fault diagnosis. If the ECM detects that the heated oxygen sensor (HO2S) 2 heater low control circuit voltage is above a specified range, DTC P0038 00 sets.

#### P0141 00

If the ECM detects that the heated oxygen sensor (HO2S) 2 heater current is not within the expected range, DTC P0141 00 sets.

### Conditions for Running the DTC

#### P0036 00, P0037 00, and P0038 00

• | The ignition is ON.

• | The Ignition Signal parameter is more than 9 V.

• | DTC P0036 00, P0037 00, and P0038 00 run continuously when the above conditions are met for 1 s.

#### P0141 00 Heater Resistance Test

• | DTCs P0036 00, P0037 00, or P0038 00, are not set.

• | The ignition is ON.

• | The Ignition Signal parameter is more than 9 V.

• | DTC P0141 00 runs continuously.

### Conditions for Setting the DTC

#### P0036 00, P0037 00, and P0038 00

• | The ECM detects that the difference between the expected and the actual HO2S 2 heater low control circuit voltage is more than a calibrated value.

• | DTCs P0036 00, P0037 00, and P0038 00 set when the above condition is met.

#### P0141 00 Heater Resistance Test

• | The ECM detects that the HO2S 2 heater resistance is more than 7000 Ω.

• | DTC P0141 00 sets within 30 s during the heater current test when the above condition is met.

### Action Taken When the DTC Sets

DTC P0036 00, P0037 00, P0038 00, P0141 00 are Type B DTCs.

### Conditions for Clearing the DTC

DTC P0036 00, P0037 00, P0038 00, P0141 00 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

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

1. Ignition OFF, disconnect the harness connector at the B52B Heated Oxygen Sensor (HO2S).
2. Ignition ON, verify that a test lamp illuminates between the B52B Heated Oxygen Sensor (HO2S) heater voltage supply circuit terminal 3 and ground.

⇒ | If the test lamp does not illuminate, test the B52B Heated Oxygen Sensor (HO2S) 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 B52B Heated Oxygen Sensor (HO2S) heater low control circuit terminal 1 and the B52B Heated Oxygen Sensor (HO2S) heater voltage supply circuit terminal 3.

⇒ | If the test lamp illuminates, test the B52B Heated Oxygen Sensor (HO2S) heater low control circuit for a short to ground. If the circuit tests normal, replace the K20 Engine Control Module (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 B52B Heated Oxygen Sensor (HO2S) heater low control circuit terminal 1 for a short to voltage or an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module (ECM).

5. If all circuits test normal, replace the appropriate B52B Heated Oxygen Sensor (HO2S).

### Repair Instructions

Caution: Refer to Heated Oxygen Sensor Resistance Learn Reset Caution in the Preface section.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Heated Oxygen Sensor Replacement - Sensor 2

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