For 1990-2009 cars

### Circuit Description

The heated oxygen sensors (HO2S) increase the amount of time the sensor spends in closed loop fuel control operation or catalyst monitoring operation. The oxygen sensor heater is required by the post-catalyst HO2S (sensor 2) in order to maintain the high operating temperatures necessary for effective operation. The heater helps provide accurate oxygen content readings of the engine exhaust by the HO2S.

### Condition for Running the DTC

The ignition is ON, or the engine is running.

### Conditions for Setting the DTC

• | The current of the HO2S heater is 5.3 amps or more with the heater ON.

• | The current of the HO2S heater is less than 0.15 amps with the heater ON.

• | The voltage of the HO2S heater is 13.8 volts or higher with the heater ON.

• | The voltage of the HO2S heater is lower than 8.7 volts with the heater ON.

• | The voltage of the HO2S heater is 6 volts with the heater OFF.

• | One of the above conditions is present for 3 seconds.

### Action Taken When the DTC Sets

• | The PCM illuminates the malfunction indicator lamp (MIL) after two consecutive ignition cycles in which the diagnostic runs with the fault active.

• | The PCM records the operating conditions at the time the diagnostic fails. This information is stored in the Freeze Frame buffer.

### Conditions for Clearing the MIL/DTC

• | The MIL turns OFF after three consecutively passing trips without a fault present.

• | A History DTC clears after 40 consecutive warm-up cycles without a fault.

• | Use the scan tool Clear DTC Information function, or disconnect the PCM battery feed in order to clear the DTC.

### Diagnostic Aids

If a DTC P0141 is intermittent, driving the vehicle under the conditions outlined in the Inspection/Maintenance (I/M) section can verify whether the fault is present. Refer to Inspection/Maintenance Heated Oxygen Sensor Heater System Set .

An intermittent malfunction may be caused by a problem in the HO2S 2 sensor heater circuit. Inspect the wiring harness and components for an intermittent condition. Refer to Intermittent Conditions .

If you cannot duplicate a DTC P0141, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.

### Test Description

The numbers below refer to the step numbers in the diagnostic table.

1. The Diagnostic System Check-Engine Controls prompts the technician to complete some basic checks and store the freeze frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

2. This step measures the resistance of the heater circuit of the HO2S. The resistance of the HO2S used on a vehicle equipped with a Warm-Up Three-Way Catalytic (TWC) converter is about half the value of a vehicle equipped without a TWC converter.

3. This step checks whether the malfunction that caused the DTC P0141 is still present. Driving the vehicle under these conditions will verify whether the fault is present. After performing the scan tool clear DTC information function, the DTC P0141 diagnostic can be monitored on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If DTC P0141 appears in the Not Ran Since Code Cleared list, the P0141 diagnostic has not yet run. When DTC P0141 does not appear in the Not Ran Since Code Cleared list, the P0141 diagnostic has run. If the MIL is NOT illuminated and there is no Pending DTC Status in DTC Information, the P0141 diagnostic has passed. The DTCs MUST be cleared in order to view the Current Status of the Not Ran Since Code Cleared list. DO NOT forget that the Not Ran Since Code Cleared list only indicates that the test has run, not whether the test passed or failed. The DTC Information screen must be checked for Current or Pending status in order to determine the outcome of the diagnostic test involved.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: Engine Controls Schematics
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | Go to Diagnostic System Check - Engine Controls
2 |

1. Turn OFF the ignition.
2. Disconnect the HO2S 2 electrical connector.
3. Turn ON the ignition, leaving the engine off.
4. Probe the harness side of the ignition feed circuit of the HO2S 2 connector using a test lamp connected to ground.

Does the test lamp illuminate?

--

Go to Step 3

Go to Step 6

3 |

1. Measure the resistance of the heater element of the HO2S.
2. Connect a digital multimeter (DMM) between terminal 3 and terminal 4, on the sensor side, of the HO2S connector.

Is the HO2S heater resistance within the specified range?

11.7-15.6 ohms at 20°C (68°F)

Go to Step 4

Go to Step 7

4 |

1. Turn OFF the ignition.
2. Connect the HO2S electrical connector.
3. Disconnect the PCM electrical connectors.
4. Turn ON the ignition, leaving the engine off.
5. Measure the voltage from the harness side of the HO2S heater control circuit at the PCM using a DMM.

Is the voltage more than the specified value?

10 V

Go to Step 9

Go to Step 5

5 | Repair the open circuit or the short to ground in the HO2S heater control circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 10 | --
6 | Repair the open in the ignition positive voltage circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 10 | --
7 |

1. Check for a faulty connection at the HO2S 2 electrical connector. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 10

Go to Step 8

8 | Replace the HO2S 2. Refer to Heated Oxygen Sensor 2 Replacement . Did you complete the replacement? | -- | Go to Step 10 | --
9 | Important: The replacement PCM must be programmed. Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 10 | --
10 |

1. Use the scan tool in order to clear the DTCs.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Operate vehicle within the Freeze Frame conditions as specified or until the HO2S heater diagnostic has run. Refer to the test description.

Does the DTC run and pass?

--

Go to Step 11

Go to Step 2

11 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List | System OK