For 1990-2009 cars

### Circuit 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. A heating element inside the HO2S minimizes the time required for the sensor to reach operating temperature. Voltage is provided to the heater by the ignition 1 voltage circuit through a fuse. With the engine running, ground is provided to the heater by the HO2S heater low control circuit, through a low side driver within the powertrain control module (PCM). The PCM commands the heater ON or OFF to maintain a specific HO2S operating temperature range. The PCM determines the temperature by measuring the current flow through the heater and calculating the resistance. Based on the resistance, the PCM can predict the sensor temperature. The HO2S 1 uses pulse width modulation (PWM) to control the heater operation. The HO2S 2 simply uses ON/OFF commands to control the heater operation. For diagnosis, the PCM monitors the heater current with the engine running. the PCM also calculates the heater resistance on a cold start. Both diagnostics will only run once per ignition cycle.

If the PCM detects that the heater current or the heater calculated resistance is not within an expected range, DTC P0141 sets for HO2S 2.

### DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0141 HO2S Heater Performance Sensor 2

### Conditions for Running the DTC

#### Heater Current Test

• | DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0117, P0118, P0120, P0121, P0125, P0128, P0201, P0202, P0203, P0204, P0205, P0220, P0442, P0443, P0446, P0449, P0452, P0453, P0455, P0496, P1516, P2101, P2176 are not set.

• | The ECT Sensor parameter is more than 70°C (158°F).

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

• | The MAF Sensor parameter is between 15-30 g/s.

• | The Engine Run Time parameter is more than 100 seconds.

• | The Engine Speed parameter is between 1,000-2,500 RPM.

• | DTC P0141 runs the heater current test 2 times per drive cycle when the above conditions are met for one second.

#### Heater Resistance Test

• | DTCs P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0117, P0118, P0120, P0121, P0125, P0128, P0201, P0202, P0203, P0204, P0205, P0220, P0442, P0443, P0446, P0449, P0452, P0453, P0455, P0496, P1516, P2101, P2176 are not set.

• | The ignition is OFF for more than 10 hours.

• | The ECT Sensor parameter is between -30 to +45°C (-22 to +113°F) at engine start-up.

• | The ECT Sensor parameter minus the IAT Sensor parameter is less than 140°C (252°F) at engine start-up.

• | The engine is running.

• | DTC P0141 runs the heater resistance test 2 times per drive cycle when the above conditions is met.

### Conditions for Setting the DTC

#### Heater Current Test

• | The PCM detects that the HO2S 2 heater current parameter is more than 1.5 amps or less than 0.199 amps.

• | DTC P0141 sets during the heater current test with 60 seconds when the above condition is met.

#### Heater Resistance Test

• | The PCM detects that the HO2S 2 heater calculated resistance is not within an expected range at engine start-up.

• | DTC P0141 sets during the heater resistance within 60 seconds when the above condition is met.

### Action Taken When the DTC Sets

• | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.

• | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

### Conditions for Clearing the MIL/DTC

• | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.

• | A current DTC, Last Test Failed, clears when the diagnostic runs and passes.

• | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.

• | Clear the MIL and the DTC with a scan tool.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 |

1. Start the engine.
2. Command the heated oxygen sensor (HO2S) 2 heater ON with a scan tool.
3. Wait 15 seconds to allow the HO2S 2 heater current to stabilize.
4. Observe the HO2S 2 heater current parameter with a scan tool.

Is the HO2S 2 heater current parameter within the specified range?

0.199-1.5 A

Go to Step 3

Go to Step 6

3 | Observe the Freeze Frame/Failure Records for this DTC. Did the DTC fail with an engine run time of less than 10 seconds? | -- | Go to Step 4 | Go to Step 5
4 |

1. Operate the vehicle within the Conditions for Running the Heater Resistance Test.
2. Start the engine.

Did the DTC fail this ignition?

--

Go to Step 6

Go to Intermittent Conditions

5 |

1. Observe the Freeze Frame/Failure Records for this DTC.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the Heater current Test. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

--

Go to Step 6

Go to Intermittent Conditions

6 |

1. Turn OFF the ignition.
2. Inspect the O2S sensor fuse.

Is the O2S sensor fuse open?

--

Go to Step 7

Go to Step 8

7 | Test the ignition 1 voltage circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 22 | Go to Step 10
8 |

1. Disconnect the HO2S 2.
2. Turn ON the ignition, with the engine OFF.
3. Probe the ignition 1 voltage circuit of the HO2S harness connector on the engine harness side with a test lamp that is connected to a good ground. Refer to Probing Electrical Connectors .

Does the test lamp illuminate?

--

Go to Step 9

Go to Step 19

9 |

1. Turn OFF the ignition.
2. Probe the HO2S heater low control circuit of the HO2S harness connector on the engine harness side with a test lamp connected to battery voltage.
3. With the ignition still OFF, observe the test lamp.

Does the test lamp illuminate?

--

Go to Step 13

Go to Step 11

10 | Test the ignition 1 voltage circuit on the sensor side of the HO2S connector for a short to ground. Refer to Circuit Testing . Is the sensor shorted to ground? | -- | Go to Step 20 | Go to Intermittent Conditions
11 | Start the engine, with the test lamp still connected from the previous step. Is the test lamp on steady or blinking? | -- | Go to Step 12 | Go to Step 14
12 | Measure the resistance of the following circuits with a DMM:

• | HO2S heater low control circuit

• | Ignition 1 voltage circuit

| Refer to Circuit Testing .

Is the resistance of either circuit more than the specified value?

3 ohms

Go to Step 18

Go to Step 16

13 | Test the HO2S heater low control circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 22 | Go to Step 17
14 | Test the HO2S heater low control circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 22 | Go to Step 15
15 | Test the HO2S heater low control circuit for an open or for high resistance. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 22 | Go to Step 17
16 | Test for shorted terminals and for poor connections at the HO2S. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 22 | Go to Step 20
17 | Test for shorted terminals and for poor connections at the powertrain control module (PCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 22 | Go to Step 21
18 | Repair the circuit with high resistance. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 22 | --
19 | Repair the open or high resistance in the ignition 1 voltage circuit. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 22 | --
20 | Notice: Refer to Heated Oxygen Sensor Resistance Learn Reset Notice in the Preface section. Replace the HO2S 2. Refer to Heated Oxygen Sensor 1 Replacement or Heated Oxygen Sensor 2 Replacement . Did you complete the replacement? | -- | Go to Step 22 | --
21 | Replace the PCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 22 | --
22 | Were you sent to this diagnostic from DTC P0140? | -- | Go to Step 18 in DTC P0140 | Go to Step 23
23 |

1. Replace the O2 sensor fuse if necessary.
2. Clear the DTCs with a scan tool.
3. Turn OFF the ignition for 30 seconds.
4. Start the engine.
5. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

--

Go to Step 2

Go to Step 24

24 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle | System OK