P0141

Diagnostic Chart (Part 1 Of 2):

Diagnostic Chart (Part 2 Of 2):

Engine Controls Schematics: Heated O2 Sensors:

CIRCUIT DESCRIPTION
Heated Oxygen Sensors are used to minimize the amount of time required for closed loop fuel control operation and to allow accurate catalyst monitoring. The oxygen sensor heater greatly decreases the amount of time required for fuel control sensor HO2S 1 to become active. The oxygen sensor heater is required by catalyst monitor sensor HO2S 2 to maintain a sufficiently high temperature. This allows accurate exhaust oxygen content readings at an increased distance from the engine.

The PCM will run the heater test only after a cold start, which is determined by the engine coolant temperature and the intake air temperature at the time of start-up. The heater test will also run only once during an ignition cycle. When the engine is started, the PCM will monitor the HO2S voltage. When the HO2S voltage indicates that the sensor is sufficiently active, the PCM determines how much time has elapsed since start-up. If the PCM determines that too much time was required for the HO2S 2 to become active, the DTC will set. The appropriate length of time for the HO2S to reach operating temperature is calculated based on the engine coolant temperature at start-up and the average mass air flow since start-up. The more total airflow and the higher the start-up engine coolant temperature, the less time should be required for HO2S activity.

CONDITIONS FOR RUNNING THE DTC
^ There are no active DTCs of any of the following types present:
^ Fuel trim
^ Fuel injector circuit
^ Misfire
^ Evaporative Emissions (EVAP)
^ Exhaust Gas Recirculation (EGR)
^ Throttle Position (TP) sensor
^ Intake Air Temperature (IAT) sensor
^ Manifold absolute pressure (MAP) sensor
^ Engine Coolant Temperature (ECT) sensor
^ Crankshaft Position (CKP) sensor
^ Mass Air Flow (MAF) sensor
^ Secondary Air Injection System (AIR)
^ DTC P0131 or P0132 is not set
^ The system voltage is between 9-18 volts.
^ The intake air temperature (IAT) is less than 45°C (113°F) at start-up.
^ The Engine Coolant Temperature (ECT) is less than 40°C (104°F) at start-up.
^ The IAT and ECT are within 15°C (27°F) of each other at start-up.
^ The average mass airflow for the sample period is less than 26 g/s.

CONDITIONS FOR SETTING THE DTC
The HO2S 2 voltage remains within 150 mV of the bias voltage (approximately 450 mV) for more time than it should. The amount of time ranges between 50-130 seconds depending on the engine coolant temperature at start-up and the average air flow since start-up.

ACTION TAKEN WHEN THE DTC SETS
^ The PCM illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
^ The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the conditions to the Freeze Frame and updates the Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The PCM turns the MIL OFF after three consecutive drive trips during which the diagnostic runs and passes.
^ A last test failed, or the current DTC, clears when the diagnostic runs and passes.
^ A History DTC clears after forty consecutive warm-up cycles, if no other emission related diagnostic failures are reported.
^ Use a scan tool in order to clear the MIL diagnostic trouble code.
^ Interrupting the PCM battery voltage may or may not clear DTCs. This practice is not recommended. Refer to Powertrain Control Module (PCM) Description, Clearing Diagnostic Trouble Codes.

DIAGNOSTIC AIDS

NOTE: Refer to Connector Test Adapter Kit J 35616-A Notice in Service Precautions.

Reviewing the Failure Records vehicle mileage since the diagnostic test last failed may help determine how often the condition occurs that caused the DTC to set. This may assist in diagnosing the condition.

If the problem is intermittent, refer to Intermittent Conditions. Intermittent Conditions

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.
2. As the heater warms the oxygen sensor to operating temperature, the HO2S will generate an output voltage proportional to the amount of oxygen in the exhaust. With the ignition ON and the engine OFF, the exhaust usually contains a high oxygen content. With the engine OFF, the HO2S voltage will usually decrease from the initial, or bias, voltage due to the high oxygen content.
4. This step checks for a correct HO2S heater ignition feed and ground supply.
5. This step checks for proper PCM and signal circuit operation.