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 P0137: HO2S Circuit Low Voltage Sensor 2
DTC P0138: HO2S Circuit High Voltage Sensor 2
DTC P013A: HO2S Slow Response Rich to Lean Sensor 2
DTC P013E: HO2S Delayed Response Rich to Lean Sensor 2
DTC P0140: HO2S Circuit Insufficient Activity Sensor 2
DTC P2232: HO2S Signal Circuit Shorted to Heater Circuit Sensor 2
DTC P2270: HO2S Signal Stuck Lean Sensor 2
DTC P2271: HO2S Signal Stuck Rich Sensor 2

### Diagnostic Fault Information

Circuit | Short to Ground | Open | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
HO2S 2 Heater Voltage Supply | Opens fuse | P0036, P0037, P0141 | -- | P0141
HO2S 2 Heater Low Control | P0036, P0037, | P0036, P0037, P0141 | P0036, P0038, P0141 | P0141
HO2S 2 Signal Hi | P0137 | -- | P0138 | --
HO2S 2 Reference Ground | -- | -- | -- | --

### Circuit/System Description

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. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature. The engine control module (ECM) supplies the HO2S with a reference, or bias, voltage of about 450 mV. When the engine is first started, the ECM operates in Open Loop, ignoring the HO2S voltage signal. Once the HO2S reaches operating temperature and Closed Loop is achieved, the HO2S generates a voltage within a range of 0-1,000 mV that fluctuates above and below bias voltage. High HO2S voltage indicates a rich exhaust stream. Low HO2S voltage indicates a lean exhaust stream.

### Conditions for Running the DTC

#### P0137

• | DTCs P0036, P0037, P0038, P0116, P0117, P0118, P0119, P0128, P2232 are not set.

• | The engine is running.

• | The Ignition 1 Signal parameter is between 10-18 volts.

• | The modeled exhaust gas temp model is more than 700°C (1,292°F) for at least 90 seconds.

• | The modeled exhaust gas temp model is less than 800°C (1,472°F).

• | The time after engine start is less than 5.1 seconds.

• | The engine coolant is more than 60°C (140°F) after last engine shut-down.

• | The engine coolant at start is less than 40°C (104°F).

• | DTC P0137 runs once per drive cycle when the above conditions are met.

#### P0138

• | The engine is running.

• | The Ignition 1 Signal parameter is between 11-18 volts.

• | The modeled exhaust gas temp model is less than 800°C (1,472°F).

• | DTC P0138 runs continuously when the above conditions are met.

#### P013A and P013E

• | The system voltage is between 11-18 volts.

• | Prior to deceleration fuel cutoff (DFCO), the HO2S 2 voltage was more than 55 mV.

• | During this drive cycle, the HO2S 2 voltage was 0.48-1.15 volts for more than 0.6 seconds.

• | The rear O2 sensor is active and has transitioned once from rich to lean.

• | The modeled exhaust gas temperature is greater than 500°C (932°F).

• | The primary air/fuel sensor is ready.

| THEN

• | The decel fuel cut-off (DFCO) is active.

• | The primary air/fuel sensor indicates lambda is greater than 3.

• | This DTC runs each time the above conditions are met.

#### P0140

• | The engine is running.

• | The HO2S 2 heater is stable, and the estimated exhaust temperature was more than 250°C (482°F) for more than 90 seconds.

• | The ignition voltage is more than 10.5 volts.

• | The estimated exhaust temperature is less than 800°C (1,472°F).

• | DTC P0140 runs continuously when the above conditions are met.

#### P2232

• | The engine is running.

• | The HO2S 2 heater is stable, and the estimated exhaust temperature was more than 250°C (482°F) for more than 90 seconds.

• | The ignition voltage is more than 10.5 volts.

• | The estimated exhaust temperature is less than 800°C (1,472°F).

• | DTC P2232 runs continuously when the above conditions are met.

#### P2270

• | The engine is running.

• | The ignition voltage is more than 10.5 volts.

• | The HO2S 2 has been in Closed Loop for more than 10 seconds.

• | DFCO is inactive.

• | The engine air flow has been between 5.56-33.33 g/sec for more than 3 seconds, and is currently more than 9.72 g/sec.

• | DTC P2270 runs continuously when the above conditions are met for 10 minutes.

#### P2271

• | DTCs P0036, P0037, P0038, P0137, P0138, P0140, P0141, P0443, P0458, P0459, P2232 are not set.

• | The engine is running.

• | The ignition voltage is more than 10.5 volts.

• | The HO2S 2 has been in Closed Loop for more than 10 seconds.

• | DFCO is inactive.

• | The engine air flow has been between 5.56-33.33 g/sec for more than 3 seconds, and is currently more than 9.72 g/sec.

• | DTC P2271 runs continuously when the above conditions are met.

### Conditions for Setting the DTC

#### P0137

• | The ECM detects that the HO2S 2 voltage parameter is less than 60 mV.

• | DTC P0137 sets within 5 seconds when the above condition is met.

#### P0138

• | The ECM detects that the HO2S 2 voltage parameter is more than 1,150 mV.

• | DTC P0138 sets within 5 seconds when the above condition is met.

#### P013A

The ECM detects that the time for the sensor voltage to transition from 0.4 to 0.2 volt exceeds 0.4 second.

#### P013E

• | The ECM detects that more than 4 seconds are required from the beginning of DFCO for the sensor voltage to fall below 0.15 volt.

| OR

• | The ECM detects that more than 8 grams of integrated air mass have passed through the system since the beginning of DFCO and the sensor voltage remains above 0.15 volt.

#### P0140

• | The ECM detects that the HO2S 2 voltage parameter is between 0.401-0.519 volt, or that the HO2S 2 internal resistance is more than 40,000 ohms while the calculated exhaust temperature is more than 500°C (932°F).

• | DTC P0140 sets within 60 seconds when the above condition is met.

#### P2232

• | The ECM detects that the HO2S 2 voltage and the HO2S 2 heater voltage changes are synchronous.

• | DTC P2232 sets within 10 seconds when the above condition is met.

#### P2270

• | The ECM detects that the HO2S 2 voltage oscillations are slower than a calibrated value.

• | DTC P2270 sets within 600 seconds when the above condition is met, or within 1,200 seconds when the fuel level is low.

#### P2271

• | The ECM detects that the HO2S 2 voltage oscillations are faster than a calibrated value.

• | DTC P2271 sets within 600 seconds when the above condition is met, or within 1,200 seconds when the fuel level is low.

### Action Taken When the DTC Sets

DTCs P0137, P0138, P013A, P013E, P0140, P2232, P2270, and P2271 are Type B DTCs.

### Conditions for Clearing the MIL/DTC

DTCs P0137, P0138, P013A, P013E, P0140, P2232, P2270, and P2271 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

• | Heated Oxygen Sensor Wiring 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. 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.
3. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

### Circuit/System Testing

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

Note: All modules must be powered down or misdiagnosis may result.

1. Ignition OFF, disconnect the scan tool and wait 60 seconds to ensure all modules are powered down.
2. Ignition OFF, disconnect the harness connector at the HO2S 2.
3. Ignition OFF, measure for less than 5 ohms between the HO2S 2 low signal circuit terminal A and ground.

⇒ | If more than the specified range, test the HO2S 2 low signal circuit for an open/high resistance. If the circuit tests normal, replace the ECM.

4. Ignition ON, verify the scan tool HO2S 2 parameter is approximately 450 mV.

⇒ | If more than the specified value, test the HO2S 2 high signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.

⇒ | If less than the specified value, test the HO2S 2 high signal circuit for a short to ground. If the circuit tests normal, replace the ECM.

5. Ignition ON, install a 3A fused jumper wire at the HO2S 2 high signal circuit terminal B. Toggle the other end of the jumper wire between the HO2S 2 low signal circuit terminal A and battery voltage. Verify the scan tool HO2S 2 parameter toggles between 0 mV and approximately 1,000 mV.

⇒ | If the scan tool HO2S 2 parameter does not toggle correctly, test the HO2S 2 high signal circuit for an open/high resistance. If the circuits test normal, replace the ECM.

6. If all circuits test normal, replace the HO2S 2.

### Repair Instructions

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

Note: For DTC P0131 and P0132, in order to ensure that the performance of the catalyst has not been affected by the fault that set this DTC, operate the vehicle within the Conditions for Running and setting DTC P0420, and verify that DTC P0420 runs and passes. Refer to DTC P0420.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Heated Oxygen Sensor Replacement - Sensor 1

• | Heated Oxygen Sensor Replacement - Sensor 2

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