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 P0133: HO2S Slow Response Sensor 1
DTC P0134: HO2S Circuit Insufficient Activity Sensor 1
DTC P0140: HO2S Circuit Insufficient Activity Sensor 2
DTC P1133: HO2S Insufficient Switching Sensor 1
DTC P2270: HO2S Signal Stuck Lean Sensor 2
DTC P2271: HO2S Signal Stuck Rich Sensor 2
DTC P2A00: HO2S Circuit Closed Loop (CL) Performance Sensor 1

### Diagnostic Fault Information

Circuit | Short to Ground | High Resistance | Open | Short to Voltage | Signal Performance
--- | --- | --- | --- | --- | ---
HO2S High Signal | P0131, P0132, P0137, P0140, P1133, P2A00 | P0131, P0132, P0133, P0134, P0137, P0140, P1133, P2A00 | P0131, P0132, P0133, P0134, P0137, P0140, P1133, P2A00 | P0132, P0134, P0138, P0140, P1133, P2A00 | P0133, P0134, P0140, P1133, P2270, P2A00
HO2S Low Signal | P2A00 | P0131, P0132, P0133, P0134, P0138, P0140, P1133, P2A00 | P0131, P0132, P0133, P0134, P0138, P0140, P1133, P2A00 | P0134, P0138, P0140, P1133, P2A00 | P2271, P2A00

### Typical Scan Tool Data

#### HO2S Sensor 1 Voltage

Circuit | Normal Range | Short to Ground | Open | Short to Voltage
--- | --- | --- | --- | ---
HO2S High Signal | 200-800 mV | 0 mV | Approximately 470 mV | Approximately 1,100 mV
HO2S Low Signal | 200-800 mV | 455 mV | Approximately 450 mV | Approximately 445 mV

### 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

#### P0133

• | DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0128, P0201, P0202, P0203, P0204, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0455, P0496, P1516, P2101, P2119, P2135, P2176 are not set.

• | The Engine Coolant Temperature (ECT) Sensor parameter is more than 70°C (158°F).

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

• | The Fuel Level Sensor parameter is more than 10 percent.

• | The Engine Run Time parameter is more than 200 seconds.

• | The Engine Speed parameter is between 1,000-3,500 RPM.

• | The Manifold Absolute Pressure (MAP) Sensor parameter is more than 30 kPa.

• | The Mass Airflow (MAF) Sensor parameter is between 11-50 g/s.

• | The Loop Status parameter is Closed.

• | The Throttle Position (TP) Indicated Angle parameter is more than 5 percent.

• | DTC P0133 runs once per drive cycle when the above conditions are met for 2 seconds.

#### P0134

• | DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0128, P0201, P0202, P0203, P0204, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0455, P0496, P1516, P2101, P2119, P2135, P2176 are not set.

• | The Engine Coolant Temperature (ECT) Sensor parameter is more than 70°C (158°F).

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

• | The engine run time is more than 200 seconds.

• | DTC P0134 runs continuously when the above conditions are met.

#### P0140

• | DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0128, P0201, P0202, P0203, P0204, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0455, P0496, P1516, P2101, P2119, P2135, P2176 are not set.

• | The ECT Sensor parameter is more than 70°C (158°F).

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

• | The Engine Run Time parameter is more than 200 seconds.

• | The Loop Status parameter is closed.

• | DTC P0140 runs once per drive cycle when the above conditions are met.

#### P1133

• | DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0128, P0201, P0202, P0203, P0204, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0455, P0496, P1516, P2101, P2119, P2135, P2176 are not set.

• | The ECT Sensor parameter is more than 70°C (158°F).

• | The Engine Speed parameter is between 1,500-3,500 RPM.

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

• | The Engine Run Time parameter is more than 200 seconds.

• | The Loop Status parameter is Closed.

• | The TP Indicated Angle parameter is more than 5 percent.

• | The Fuel Level Sensor parameter is more than 10 percent.

• | The MAP Sensor parameter is more than 30 kPa.

• | The MAF Sensor parameter is between 11-50 g/s.

• | DTC P1133 runs once per drive cycle when the above conditions are met for 2 seconds.

#### P2270

• | DTCs P0030, P0036, P0053, P0054, P0101, P0102, P0103, P0106, P0107, P0108, P0120, P0121, P0122, P0123, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P013A, P013B, P013E, P013F, P0140, P0141, P0171, P0172, P0201, P0202, P0203, P0204, P0220, P0222, P0223, P0300, P0442, P0443, P0446, P0449, P0455, P0496, P1133, P1174, P1516, P2101, P2119, P2135, P2176, P2270, P2271, P2A00 are not set.

• | The system voltage is between 10-18V.

• | The learned heater resistance is valid.

• | The ICAT MAT Burnoff delay is not active.

• | The Green O2 Sensor Condition is not present.

• | The fuel level is more than 10 percent or the fuel level data fault is active.

• | Engine run time is equal to or more than 40 seconds.

| THEN

• | DTCs are not active.

• | The engine speed is between 1,100-2,100 RPM.

• | Airflow is equal to or more than 3 g/s and equal to or less than 12 g/s.

• | The vehicle speed is equal to or more than 73 km/h (45.4 mph) and equal to or less than 120 km/h (74.6 mph).

• | The short term fuel trim is equal to or more than 0.9 and equal to or less than 1.065.

• | The fuel state is in closed loop.

• | The EVAP diagnostics are not in control of purge.

• | The Ethanol Estimate is not in progress.

• | The Post Cell Enabled.

• | The Power Take-Off is not active.

• | The EGR diagnostic is not intrusive.

• | The Heater Warm-up Delay is more than 120 seconds.

• | The catalytic converter temperature is equal to or more than 650°C (1,202°F), and equal to less than 900°C (1,652°F).

• | This DTC runs once per trip when all of the above conditions have been met for 2 seconds.

#### P2271

• | DTCs P0030, P0036, P0053, P0054, P0101, P0102, P0103, P0106, P0107, P0108, P0120, P0121, P0122, P0123, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P013A, P013B, P013E, P013F, P0140, P0141, P0171, P0172, P0201, P0202, P0203, P0204, P0220, P0222, P0223, P0300, P0442, P0443, P0446, P0449, P0455, P0496, P1133, P1174, P1516, P2101, P2119, P2135, P2176, P2270, P2271, P2A00 are not set.

• | The system voltage is between 10-18V.

• | The learned heater resistance is valid.

• | The ICAT MAT Burnoff delay is not active.

• | The Green O2 Sensor Condition is not present.

• | The fuel level is more than 10 percent or the fuel level data fault is active.

• | Engine run time is equal to or more than 40 seconds.

| THEN

• | DFCO is active.

• | APP is stable.

• | TCC is locked.

• | DTC P013A, P013E, and P2270 have run and passed.

• | This DTC runs once per trip.

#### P2A00

• | DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0128, P0201, P0202, P0203, P0204, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0455, P0496, P1516, P2101, P2119, P2135, P2176 are not set.

• | The Engine Run Time parameter is more than 100 seconds.

• | The Engine speed parameter is between 1,000-3,400 RPM.

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

• | The Mass Airflow (MAF) Sensor parameter is between 10-30 g/s.

• | The ECT Sensor parameter is more than 70°C (158°F).

• | DTC P2A00 runs continuously when the above conditions are met for 5 seconds.

### Conditions for Setting the DTC

#### P0133

• | The ECM detects that the HO2S 1 rich-to-lean or lean-to-rich average response time is more than 0.1 second.

• | DTC P0133 sets within 60 seconds when the above condition is met.

#### P0134

• | The ECM detects that the HO2S 1 parameter is between 400-500 mV for 100 seconds.

• | The Throttle Position (TP) Indicated Angle parameter changes more than 1 percent, 3 times.

• | DTC P0134 sets within 100 seconds when the above conditions are met.

#### P0140

• | The ECM detects that the HO2S 2 parameter is between 425-475 mV.

• | The TP Indicated Angle parameter changes more than 1 percent 3 times.

• | DTC P0140 sets within 100 seconds when the above conditions are met.

#### P1133

• | The ECM detects that the HO2S 1 rich-to-lean counts, or the lean-to-rich counts are less than a calibrated value.

• | DTC P1133 sets within 60 seconds when the above condition is met.

#### P2270

• | The ECM detects that the O2 sensor cannot achieve voltage equal to or more than 775 mV.

| AND

• | The ECM detects that the accumulated mass air flow monitored during the Stuck Lean Voltage Test is more than 45 grams.

#### P2271

• | The ECM detects that the O2 sensor cannot achieve voltage equal to or less than 100 mV.

| AND

• | The ECM detects that the accumulated mass air flow monitored during the Stuck Rich Voltage Test is more than 20 grams.

#### P2A00

• | The ECM detects that the Loop Status parameter is open.

• | DTC P2A00 sets within 50 seconds when the above condition is met.

### Action Taken When the DTC Sets

DTCs P0133, P0134, P0140, P1133, P2270, P2271, P2A00 are Type B DTCs.

### Conditions for Clearing the MIL/DTC

DTCs P0133, P0134, P0140, P1133, P2270, P2271, P2A00 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. If any HO2S heater DTCs are set, perform those diagnostics first.
2. Allow the engine to reach operating temperature.
3. Engine running, observe the affected HO2S parameter with a scan tool.

• | The pre-catalyst oxygen sensors value should vary from below 200 mV to above 800 mV and respond to fueling changes.

• | The post-catalyst oxygen sensors value should change more than 200 mV when the throttle is quickly cycled 3 times from closed to wide open and back to closed after running the engine at 1,500 RPM for 30 seconds.

4. The affected HO2S may be damaged due to contamination. Prior to replacing the affected HO2S, inspect for the following sources of contamination:

Notice: Refer to Silicon Contamination of Heated Oxygen Sensors Notice in the Preface section.

• | A silicon contaminated HO2S

• | Fuel contamination--Refer to Alcohol/Contaminants-in-Fuel Diagnosis .

• | Engine oil consumption--Refer to Oil Consumption Diagnosis .

• | Engine coolant consumption--Refer to Loss of Coolant .

5. 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

Important: 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 appropriate HO2S.
3. Ignition OFF, measure for less than 5 ohms resistance between the appropriate HO2S low signal circuit terminal A and ground.

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

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

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

⇒ | If less than the specified value, test the appropriate HO2S 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 high signal circuit terminal B. Toggle the jumper wire between the HO2S low signal circuit terminal A and battery voltage. Verify the appropriate scan tool HO2S parameter toggles between 0 mV and approximately 1,000 mV.

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

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

### Repair Instructions

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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Heated Oxygen Sensor 1 Replacement

• | Heated Oxygen Sensor 2 Replacement

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