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 P0131: O2 Sensor Circuit Low Voltage (Bank 1 Sensor 1)
DTC P0132: O2 Sensor Circuit High Voltage (Bank 1 Sensor 1)
DTC P0137: O2 Sensor Circuit Low Voltage (Bank 1 Sensor 2)
DTC P0138: O2 Sensor Circuit High Voltage (Bank 1 Sensor 2)
DTC P0151: O2 Sensor Circuit Low Voltage (Bank 2 Sensor 1)
DTC P0152: O2 Sensor Circuit High Voltage (Bank 2 Sensor 1)
DTC P0157: O2 Sensor Circuit Low Voltage (Bank 2 Sensor 2)
DTC P0158: O2 Sensor Circuit High Voltage (Bank 2 Sensor 2)
DTC P2A01: O2 Sensor Circuit Range/Performance (Bank 1 Sensor 2)
DTC P2A04: O2 Sensor Circuit Range/Performance (Bank 2 Sensor 2)

### Diagnostic Fault Information

Circuit | Short to Ground | High Resistance | Open | Short to Voltage | Signal Performance
--- | --- | --- | --- | --- | ---
HO2S High Signal | P0131, P0132, P0137, P0140, P0151, P0152, P0157, P0158, P1133, , P2A04 | P0131, P0132, P0133, P0134, P0137, P0140, P0151, P0152, P0153, P0154, P0157, P0160, P1133, P1153, | P0131, P0132, P0133, P0134, P0137, P0140, P0151, P0152, P0153, P0154, P0157, P0160, P1133, P1153, | P0132, P0134, P0138, P0140, P0152, P0154, P0158, P0160, P1133, P1153, | P0133, P0134, P0140, P0153, P0154, P0160, P1133, P1153,
HO2S Low Signal | P2A00, P2A01, P2A03, P2A04 | P0131, P0132, P0133, P0134, P0138, P0140, P0151, P0152, P0153, P0154, P0158, P0160, P1133, P1153, | P0131, P0132, P0133, P0134, P0138, P0140, P0151, P0152, P0153, P0154, P0158, P0160, P1133, P1153, | P0134, P0138, P0140, P0154, P0158, P0160, P1133, P1153, , |

### 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.

#### P2A01, or P2A04

The HO2S are used for catalyst monitoring. During this test the ECM will force the air-to-fuel ratio rich and/or lean. The ECM then waits for a predicted response from the sensor. If the sensor voltage transitions below 200 mV and/or above 730 mV, the DTC will pass for this ignition cycle.

### Conditions for Running the DTC

#### P0131 or P0151

• | DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0220, P0222, P0223, P0443, P1516, P2101, P2119, P2135 or P2176 are not set.

• | The Loop Status parameter is Closed.

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

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

• | The Throttle Position (TP) Indicated Angle parameter is between 3-70 percent.

• | DTC P0131 runs continuously when the above conditions are met for 3 seconds.

#### P0132 or P0152

• | DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0220, P0222, P0223, P0442, P0443, P1516, P2101, P2119, P2135 or P2176 are not set.

• | The Loop Status parameter is Closed.

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

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

• | The Throttle Position (TP) Sensor parameter is between 3-70 percent.

• | DTC P0132 runs continuously when the above conditions are met for 2 seconds.

#### P0137 or P0157

• | DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0220, P0222, P0223, P0442, P0443, P1516, P2101, P2119, P2135 or P2176 are not set.

• | The Loop Status parameter is Closed.

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

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

• | The TP Sensor parameter is between 3-70 percent.

• | DTC P0137 runs the lean test continuously when the above conditions are met for 3 seconds.

#### P0138 or P0158

• | DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0220, P0222, P0223, P0442, P0443, P1516, P2101, P2119, P2135 or P2176 are not set.

• | The Loop Status parameter is Closed.

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

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

• | The TP Sensor parameter is between 3-70 percent.

• | DTC P0138 runs the rich test continuously when the above conditions are met for 3 seconds.

#### P2A00 and P2A03

• | DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0220, P0222, P0223, P0442, P0443, P1516, P2101, P2119, P2135 or 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 air flow (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.

#### P2A01 and P2A04 Intrusive Test

• | DTCs P0030, P0036, P0053, P0054, P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0128, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0140, P0141, P0201, P0202, P0203, P0204, P0205, P0206, P0207, P0208, P0220, P0222, P0223, P0442, P0443, P0446, P0449, P0455, P0496, P1133, P1516, P2101, P2119, P2135, P2176, P2A00 are not set.

• | The Engine Run Time parameter is more than 9.6 minutes.

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

• | The MAF sensor parameter is between 3-50 g/s.

• | The Engine Speed parameter is between 500-5,000 RPM.

• | The Vehicle Speed parameter is between 55-132 km/h (34-82 mph).

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

• | The Short Term FT parameter is between -4 and +6 percent.

• | DTC P2A01 runs the intrusive test once per drive cycle when the above conditions are met for 5 second.

### Conditions for Setting the DTC

#### P0131 or P0151

• | The ECM detects that the sensor Voltage parameter is less than 80 mV.

• | DTC P0131 sets within 50 seconds during the lean test when the above condition is met.

#### P0132 or P0152

• | The ECM detects that the sensor parameter is more than 1,050 mV.

• | DTC P0132 sets within 50 seconds during the rich test when the above condition is met.

#### P0137 or P0157

• | The ECM detects that the sensor voltage parameter is less than 80 mV.

• | DTC P0137 sets within 100 seconds during the lean test when the above condition is met.

#### P0138 or P0158

• | The ECM detects that the sensor voltage parameter is more than 950 mV.

• | DTC P0138 sets within 100 seconds during the rich test when the above condition is met.

#### Lean Intrusive Test

1. The ECM detects that the sensor is more than 200 mV for 12 seconds.
2. The pre-catalytic on the same bank is less than 300 MV.

#### Rich Intrusive Test

1. The ECM detects that the sensor is less than 730 mV for 12 seconds.
2. The sensor is more than 730 mV.
3. DTC P2A01 sets within 10 minutes when the above conditions are met.

### Action Taken when the DTC Sets

DTCs P0131, P0132, P0137, P0138, P0151, P0152, P0157, P0158, P2A01 or P2A04 are type B DTCs.

### Conditions for Clearing the MIL/DTC

DTCs P0131, P0132, P0137, P0138, P0151, P0152, P0157, P0158, P2A01 or P2A04 are type B DTCs.

### Reference Information

#### Schematic Reference

Engine Controls Schematics

#### Connector End View Reference

Component Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

• | Heated Oxygen Sensor Wiring Repairs

#### Scan Tool Reference

Control Module References

### Circuit/System Verification

• | Allow the engine to reach operating temperature. Engine running, using a scan tool observe the affected HO2S parameter.

- | The HO2S 1 value should vary from below 200 mV to above 800 mV and respond to fuelling changes.

- | The HO2S 2 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.

• | If any HO2S heater DTCs are set, diagnose those DTCs first.

• | 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

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

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

### Circuit/System Testing

1. Disconnect the affected HO2S.
2. Ignition ON, measure for approximately 2-40 mV from the affected HO2S low signal circuit terminal to a known ground.

⇒ | If more than approximately 40 mV, test the affected HO2S low signal circuit for a short to voltage. If the circuit tests normal, ECM.

⇒ | If less than approximately 2 mV, test the affected HO2S low signal circuit for open/high resistance. If the circuit tests normal, replace the ECM.

3. Measure for approximately 300 mV from the affected HO2S high signal circuit terminal and a known ground.

⇒ | If more than approximately 300 mV, test the affected HO2S high signal circuit for a short to voltage. If the circuit tests normal, replace the ECM.

⇒ | If less than approximately 300 mV, test the affected HO2S high signal circuit for high resistance. If the circuit tests normal, replace the ECM.

4. Install a 3-A fusible link wire between the affected HO2S high signal circuit terminal and the affected HO2S low signal circuit terminal. The affected HO2S parameter should indicate 0 mV.

⇒ | If not 0 mV and all circuits and connectors test normal, replace the ECM.

5. Install a test lamp between the affected HO2S high signal circuit terminal B and battery voltage. The affected HO2S parameter should indicate approximately 1,095 mV.

⇒ | If not 1,095 mV and all circuits and connectors test normal, replace the ECM.

6. If the ECM and all circuits test normal, replace the affected HO2S.

### Repair Instructions

Notice: Refer to Diagnostic System Check - Vehicle in the Preface section.

Important:

• | Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | For DTC P0131 and P0132, in order to make sure 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 P0420 runs and passes. Refer to DTC P0420 or P0430.

• | Heated Oxygen Sensor Replacement - Bank 1 Sensor 2.

• | Heated Oxygen Sensor Replacement - Bank 2 Sensor 2.

• | Engine Control Module Replacement for engine control module replacement, setup and programming.