For 1990-2009 cars
Engine Controls Components
Cell 20: Heated Oxygen Sensors
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

The heated oxygen sensor (HO2S) produces a voltage that varies between -100 mV and 900 mV under normal operating conditions. On the Catera, the full operating range of the HO2S circuit is approximately from -406 mV to 1124 mV. The Engine Control Module (ECM) monitors this voltage and determines if the exhaust is lean or rich. The oxygen sensor voltage is high when the exhaust is rich, and low when the exhaust is lean. The ECM constantly monitors the HO2S signal during the closed loop operation and compensates for a rich or lean condition by decreasing or increasing the injector pulse width as necessary. If the oxygen sensor is slow to respond to any changes in the exhaust oxygen content, this DTC will set.

### Conditions for Running the DTC

• | None of the following DTCs are set: P0120, P0135, P0141, P0155, P0161, P0340, P0440, P0441, P0442, P0443, P0455, P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0560.

• | A closed loop operation

• | The engine speed is between 1,000 RPM and 2,000 RPM.

• | The engine load signal is between 1.3 ms and 3.0 ms.

• | The calculated TWC temperature is greater than 352°C (666°F).

• | More than 6 seconds have passed since the purge enabled.

### Conditions for Setting the DTC

The HO2S averaged response rate is greater than 3.3 seconds.

### Action Taken When the DTC Sets

The ECM illuminates the malfunction indicator lamp (MIL) and records the operating conditions in the Freeze Frame on the second consecutive drive trip that the diagnostic runs and fails.

### Conditions for Clearing the MIL/DTC

• | The ECM turns OFF the MIL after three consecutive drive trips that the diagnostic runs and passes.

• | A History DTC clears after forty consecutive warm-up cycles in which no failures are reported by this diagnostic or any other emission related diagnostic.

• | The ECM battery voltage is interrupted.

• | The scan tool clears the MIL/DTC.

### Diagnostic Aids

Use the Connector Test Adapter Kit J 35616 for any test that requires probing the ECM harness connector or a component harness connector. Using this kit will prevent damage to the harness connector terminals.

Check for the following conditions:

• | The sensor pigtail or the harness may be mis-positioned and contacting the exhaust system.

• | Heated oxygen sensor wiring. Inspect the harness connectors for the following conditions:

- | Backed out terminals

- | Improper mating

- | Broken locks

- | Improperly formed or damaged terminals

- | Poor terminal to wire connection

- | Corrosion and water intrusion

Refer to Engine Control Module Diagnosis, Checking Terminal Contact for the proper procedure. An oxygen supply inside of the HO2S is necessary for a proper operation. This supply of oxygen is provided through the HO2S wires. All of the HO2S wires and connections should be inspected for any breaks or any contamination. If any of the wiring repairs need to be made, refer to Electrical Diagnosis in Engine El

### Test Description

The number(s) below refer to step numbers on the diagnostic table:

1. The engine must be at the normal operating temperature before performing this test.

#### DTC P0133 - Heated Oxygen Sensor (HO2S) Slow Response Bank 1 Sensor 1

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 | Is DTC P0153 also set? | -- | Go to Step 7 | Go to Step 3
3 | Perform the Exhaust System Leak Test. If an exhaust leak is found, repair as necessary, then return to this diagnostic. Refer to Exhaust System. Was a problem found and corrected? | -- | Go to Step 27 | Go to Step 4
4 | Visually/physically inspect the following items:

• | Ensure that the HO2S is securely installed.

• | Check for corrosion on the terminals.

• | Check the terminal tension (at the HO2S and at the ECM). Refer to Electrical Diagnosis in Engine Electrical, and Troubleshooting Procedures for the proper procedure. Also, refer to Checking Terminal Contact in Engine Control Module Diagnosis .

• | Check for any damaged wiring.

Was a problem found and corrected?

--

Go to Step 27

Go to Step 5

5 |

1. Disconnect the HO2S.
2. Monitor the HO2S voltage with a scan tool.

Does the scan tool indicate voltage within the specified values?

375-525 mV

Go to Step 6

Go to Step 8

6 |

1. Jumper the HO2S Signal and Low circuits to ground in the harness connector.
2. Monitor the HO2S voltage with the scan tool.

Does the scan tool indicate the voltage below the specified value?

-100 mV

Go to Step 17

Go to Step 8

7 | Notice: Correct the source of the oxygen sensor contamination before replacing the sensor in order to prevent future contamination. Typical contamination sources include the following:

• | Fuel contamination

• | Use of improper RTV sealant

• | Engine oil or engine coolant consumption

Replace the affected Heated Oxygen Sensors. Refer to HO2S replacement.

Is the action complete?

--

Go to Step 16

--

8 | Measure the voltage from the HO2S signal circuit in the HO2S harness connector to ground with the DVM J 39200 . Is the voltage within the specified range? | 900-1100 mV | Go to Step 9 | Go to Step 14
9 | Measure the voltage from the HO2S Low circuit in the HO2S harness connector to ground with the DVM J 39200 . Is the voltage within the specified range? | 700-800 mV | Go to Step 26 | Go to Step 10
10 |

1. Continue to monitor the voltage from the HO2S Low circuit in the HO2S harness connector to ground.
2. Disconnect the other three HO2S. As each sensor is disconnected, recheck the voltage on the DVM.

Does disconnecting one of the other sensors restore the voltage to the specified range?

700-800 mV

Go to Step 18

Go to Step 11

11 |

1. Leave all of the HO2S disconnected.
2. Disconnect the ECM.
3. Turn on the ignition.
4. Measure the voltage from the HO2S Low circuit in the ECM harness connector to battery ground with the DVM J 39200 .

Is there any voltage present?

--

Go to Step 19

Go to Step 12

12 | Check the harness for continuity of the HO2S Low circuit with the DVM J 39200 . Is the continuity indicated? | -- | Go to Step 13 | Go to Step 20
13 | Check the harness for continuity between the HO2S Low circuit and battery ground with the DVM J 39200 . Is continuity indicated? | -- | Go to Step 21 | Go to Step 25
14 |

1. Leave the HO2S disconnected.
2. Disconnect the ECM.
3. Turn on the ignition.
4. Measure the voltage from the HO2S Signal circuit in the ECM harness connector to battery ground with the DVM J 39200 .

Is there any voltage present?

--

Go to Step 22

Go to Step 15

15 | Check the harness for continuity of the HO2S Signal circuit with the DVM J 39200 . Is continuity indicated? | -- | Go to Step 16 | Go to Step 23
16 | Check the harness for continuity between the HO2S Signal circuit and battery ground with the DVM J 39200 . Is continuity indicated? | -- | Go to Step 24 | Go to Step 25
17 | Replace the HO2S. Is the action complete? | -- | Go to Step 27 | --
18 | Replace the shorted HO2S. Is the action complete? | -- | Go to Step 27 | --
19 | Repair the HO2S Low circuit shorted to voltage. Is the action complete? | -- | Go to Step 27 | --
20 | Repair the open/high resistance in the HO2S Low circuit. Is the action complete? | -- | Go to Step 27 | --
21 | Repair the short to ground in the HO2S Low circuit. Is the action complete? | -- | Go to Step 27 | --
22 | Repair the signal circuit that is shorted to voltage. Is the action complete? | -- | Go to Step 27 | --
23 | Repair the open/high resistance in the signal circuit. Is the action complete? | -- | Go to Step 27 | --
24 | Repair the short to ground in the signal circuit. Is the action complete? | -- | Go to Step 27 | --
25 | Check for a poor connection or poor terminal tension at the ECM harness connector. Refer to Electrical Diagnosis in Engine Electrical, and Troubleshooting Procedures for the proper procedure. Also, refer to Checking Terminal Contact in Engine Control Module Diagnosis .

Was a problem found and corrected?

--

Go to Step 27

Go to Step 26

26 | Important: This vehicle is equipped with a Theft Deterrent System which interfaces with the Engine Control Module (ECM). Program the new ECM with the frequency code of the theft deterrent module that is currently on the vehicle. Replace the ECM. Refer to Engine Control Module Replacement/Programming .

Is the action complete?

--

Go to Step 27

--

27 |

1. Clear the DTCs with the scan tool.
2. Turn off the ignition for 15 seconds.
3. Start the engine.
4. Operate the vehicle within the conditions required for this diagnostic to run. Refer to Conditions for Running the DTC.
5. Check for any DTCs.

Is this DTC set?

--

Go to Step 2

Go to Step 28

28 | Were there any additional DTCs noted during the Powertrain OBD System Check that have not been diagnosed? | -- | Go to the applicable DTC table | The System is OK