For 1990-2009 cars
Engine Controls Components
Cell 23: EVAP and EGR Controls
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 converts any harmful exhaust emissions into harmless water vapor and carbon dioxide.

The Powertrain Control Module (PCM) has the capability to monitor this process by using a rear heated oxygen sensor (HO2S 2). The HO2S 2 , located in the exhaust stream past 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).

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

• | Damaged wiring

• | Damaged electrical connectors

• | 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 for the HO2S 2 to function properly. This clean air reference is obtained by way of the HO2S 2 wires.

### Conditions for Running the DTC

None of the following DTCs set: P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0171, P0200, P0300, P0335, P0440, P0442, P0446, P0506, P0507, P0601, P0602 and P1441.

• | Engine Coolant Temperature (ECT) less than 45°C (113°F).

• | Intake Air Temperature (IAT) less than 45°C (113°F).

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

• | Throttle Position (TP) is less than 18 percent.

• | Engine run time is less than 400 seconds.

• | Average air flow is less than 20 (g/sec).

• | Battery voltage between 11.6 and 16V.

### Conditions for Setting the DTC

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

### Action Taken When the DTC Sets

• | The malfunction indicator lamp (MIL) will illuminate after two 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 MIL/DTC

• | The MIL will turn OFF after three 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.

• | The MIL/DTCs can be cleared by using the scan tool.

### Diagnostic Aids

An intermittent could be the result of the following conditions:

• | A poor electrical connection

• | Moisture in the connector/wiring

• | Rubbed-through wire insulation

• | A broken wire inside the insulation

Check for a poor electrical connection or a damaged harness. Inspect the harness electrical connectors for the following conditions:

• | Improper mating

• | Broken locks

• | Improperly-formed electrical connectors

• | Damaged terminals

• | A poor terminal-to-wire connection

• | A damaged harness

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

• | Damaged wiring

• | Damaged electrical connectors

• | 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 for the HO2S 2 to function properly. This clean air reference is obtained by way of the HO2S 2 wires.

### Test Description

An example test description follows:

1. The Powertrain OBD System Check prompts you to complete some of the basic checks and to store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data captured when the malfunction occurred. The scan tool stores this data for later reference.

2. 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 displayed on the scan tool should change within several minutes towards 0 or 1 volt, indicating that the heater is working properly.

3. Probing terminal D of the HO2S 2 electrical connector verifies if the voltage is available to the HO2S 2 heater.

4. If the voltage is available at the electrical connector, then the connector becomes a good voltage source to check for a ground at terminal C.

5. This step determines if the voltage is not available at the HO2S 2 due to an open O2 fuse or open ignition feed circuit. If the fuse is open, determine if the open fuse was due to a short in the ignition feed circuit or shorted HO2S 2 before replacing the fuse.

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

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 |

Important: If the engine has just been operating, allow the engine to cool for the specified condition to running this DTC.

1. Turn ON the ignition switch leaving the engine OFF.
2. Install a scan tool.

Does the HO2S 2 voltage gradually change towards the specified voltage?

0 V or 1 V

Go to Step 13

Go to Step 3

3 |

1. Turn OFF the ignition switch.
2. Disconnect the HO2S 2 electrical connector.
3. Turn ON the ignition switch leaving the engine OFF.
4. Connect a test light to ground.
5. Probe the ignition feed circuit (PCM side) of the electrical connector.

Does the test light illuminate?

--

Go to Step 4

Go to Step 5

4 | Connect a test light between the following circuits (PCM side) of the HO2S 2 electrical connector.

• | Ignition feed

• | Ground circuits

Does the test light illuminate?

--

Go to Step 6

Go to Step 7

5 | Inspect the ERLS fuse in the fuse block. Is the ERLS fuse open? | -- | Go to Step 8 | Go to Step 9
6 |

1. Turn OFF the ignition switch.
2. Check the electrical connections at the HO2S 2 electrical connector.
3. Repair the electrical connections as necessary.

Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 13

Go to Step 10

7 |

1. Turn OFF the ignition switch.
2. Check the electrical connections at the HO2S 2 electrical connector.
3. Repair the electrical connections as necessary. Refer to Wiring Repairs in Wiring Systems..

Was a repair necessary?

--

Go to Step 13

Go to Step 11

8 |

1. Check for a short to ground in the HO2S 2 ignition feed circuit.
2. Repair the circuit if necessary. Refer to Wiring Repairs in Wiring Systems.
3. Replace the open fuse.

Was a repair necessary?

--

Go to Step 13

Go to Step 10

9 |

1. Turn OFF the ignition switch.
2. Check the electrical connections at the HO2S 2 electrical connector.
3. Repair the electrical connections as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 13

Go to Step 12

10 |

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

Is the action complete?

--

Go to Step 13

--

11 | Repair the open in the ground circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 13 | --
12 | Repair the open in the ignition feed circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | Go to Step 13 | --
13 |

1. Clear the DTCs with the scan tool.
2. Start the engine.
3. Idle the engine at the normal operating temperature.
4. Operate the vehicle within the conditions for running this DTC as specified in the supporting text.

Does the scan tool indicate that this diagnostic has and passed?

--

Go to Step 14

Go to Step 2

14 | Check to see if any additional DTCs are set. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to applicable DTC table | System OK