For 1990-2009 cars
Engine Controls Components
Power, Ground, HO2S 2, and O2S 1
OBD II Symbol Description Notice
Powertrain Control Module Connector End Views
Handling ESD Sensitive Parts Notice

### Circuit Description

In order to control emissions, a catalytic converter is used to convert harmful exhaust gases into harmless water vapors and carbon dioxide.

The PCM has the capability of monitoring this process by using a rear heated oxygen sensor (HO2S 2). The HO2S 2, located in the exhaust stream behind the catalytic converter, produces an output signal which indicates the storage capacity of the catalyst. This in turn indicates the catalyst's ability to convert the exhaust emissions effectively. If the catalyst is functioning properly, the HO2S 2 signal will be far less active than the signal produced by the front oxygen sensor (O2S 1).

### Conditions for Running the DTC

The following DTCs are not set: P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0171, P0201, P0202, P0203, P0204, P0300, P0335, P0440, P0442, P0446, P0506, P0507, P0601, P0602 and P1441.

• | The engine coolant temperature (ECT) is less than 45°C (113°F).

• | The intake air temperature (IAT) is less than 45°C (113°F).

• | The difference between the ECT and the IAT is less than 7°C (13°F).

• | The throttle position (TP) is less than 18 percent.

• | The engine run time is less than 400 seconds.

• | The average air flow is less than 20 g/s.

• | The battery voltage is between 11.6 and 16 V.

### Conditions for Setting the DTC

The HO2S 2 voltage increases less than 150 mV in a certain number of seconds, based upon airflow (g/sec).

### Action Taken When the DTC Sets

• | The Malfunction Indicator Lamp (MIL) will illuminate after 2 consecutive ignition cycles in which the diagnostic runs with the malfunction present.

• | The PCM will record the operating conditions at the time that the diagnostic fails. This information will store in the Freeze Frame and Failure Records buffers.

• | A history DTC stores.

### Conditions for Clearing the DTC

• | The MIL will turn off after 3 consecutive ignition cycles in which the diagnostic runs without a fault.

• | A history DTC will clear after 40 consecutive warm up cycles without a fault.

• | Clear the DTC with a scan tool.

### Diagnostic Aids

• | Inspect the exhaust system for the following conditions:

- | Any leaks between the 3-way catalytic converter and the flange.

- | Any corrosion between the 3-way catalytic converter and the flange

- | Any loose or missing hardware between the 3-way catalytic converter and the flange

• | A poor electrical connection or a damaged harness. Inspect the harness for a short to ground in the HO2S 2 signal circuit. Ensure that the HO2S 2 pigtail is not contacting the exhaust.

| Inspect for the following conditions:

- | Any wiring contacting the exhaust system

- | Any incorrect mating

- | Any broken locks

- | Any incorrectly formed harness connectors

- | Any damaged terminals

- | A poor terminal-to-wire connection

- | A damaged harness

• | Observe the HO2S 2 on a scan tool while moving any of the related connectors and the wiring harness with the ignition on. If the malfunction is induced, the HO2S 2 display will change. This should help isolate the location of the malfunction.

An intermittent could be the result of the following conditions:

• | A poor electrical connection

• | A rubbed-through wire insulation

• | A broken wire inside of the insulation

Do not attempt to repair the HO2S 2. Replace the HO2S 2 assembly if the following conditions exist:

• | Any damaged wiring

• | A damaged connector

• | Any damaged terminals

Obstruction of the air reference and degraded HO2S 2 performance could result from any attempt to repair the above conditions.

The HO2S 2 must have a clean air reference in order to function properly. This clean air reference is obtained by the HO2S 2 wires.

### Test Description

An example test description follows:

1. This step determines if DTC P0141 is the result of a hard malfunction or an intermittent condition. With the ignition switch on and the engine off, the HO2S 2 voltage should change within several minutes towards 0 or 1 volt, indicating that the heater is working properly.

2. This step determines if the HO2S 2 has a internal short.

3. This step determines if the HO2S 2 has a internal open.

#### DTC P0141-Heated Oxygen Sensor (HO2S) Heater Circuit (Sensor 2)

Step | Action | Values | 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 | Important: The HO2S must be cool before proceeding with diagnosis. The Ignition must remain OFF for at least one half hour before proceeding with diagnosis.

1. Connect the scan tool.
2. Set-up the scan tool with the proper vehicle identification information prior to turning the ignition ON.
3. Turn ON the ignition leaving the engine OFF.
4. As quickly as possible observe and record the HO2S voltage for the sensor that applies to this DTC.
5. Monitor the HO2S voltage for two minutes.

Does the HO2S voltage increase or decrease from the initial voltage by at least the value specified?

150 m V

Go to Diagnostic Aids

Go to Step 3

3 | Test the ERLS fuse. Did you find an open fuse? | -- | Go to Step 4 | Go to Step 5
4 |

1. Turn off the ignition.
2. Allow the engine to cool for 10 minutes.
3. Disconnect the HO2S 2 connector.
4. Connect a DMM between the HO2S 2 ignition feed circuit and ground circuit at the sensor pigtail.

Is the HO2S 2 heater resistance within the specified range?

4-6 ohms

Go to Step 9

Go to Step 10

5 |

1. Turn off the ignition.
2. Disconnect the HO2S 2 connector.
3. Turn on the ignition, leaving the engine off.
4. Connect a test lamp to a known good ground.
5. Probe the ignition feed circuit at the connector.

Does the test lamp illuminate?

--

Go to Step 6

Go to Step 7

6 | Connect the test lamp between the HO2S 2 ignition feed circuit and the ground circuit at the connector. Does the test lamp illuminate? | -- | Go to Step 10 | Go to Step 8
7 |

1. Turn off the ignition.
2. Inspect the HO2S 2 ignition feed circuit for the following conditions:

• | An open

• | Any poor connections

3. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 11

--

8 |

1. Turn off the ignition.
2. Inspect the HO2S 2 ground circuit for the following conditions:

• | An open

• | Any poor connections

3. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 11

--

9 |

1. Repair the short to ground in the HO2S 2 ignition feed circuit.
2. Replace the open fuse.

Did you complete the repair?

--

Go to Step 11

--

10 |

1. Replace the HO2S 2. Refer to Heated Oxygen Sensor Replacement .
2. Replace the fuse if necessary.

Did you complete the repair?

--

Go to Step 11

--

11 |

1. Use a scan tool to clear the DTCs.
2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

--

Go to Step 2

System OK