P0141
DTC P0141: HO2S Heater Performance Sensor 2Wiring Diagram:
Circuit Description
Heated oxygen sensors are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is first started, the engine control module (ECM) operates in an open loop mode, ignoring the HO2S signal voltage when calculating the air fuel ratio. The ECM supplies the HO2S with a reference voltage of about 0.45 V. The HO2S generates a voltage within a range of 0 - 1 V that fluctuates above and below bias voltage once in closed loop. A high HO2S voltage output indicates a rich fuel mixture. A low HO2S voltage output indicates a lean mixture. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature, and then provide an accurate voltage signal.
The ECM controls the heater by grounding the control circuit with a solid state device called a driver. The driver is equipped with a feedback circuit. The ECM can determine if the control circuit is open, shorted to ground, or shorted to a voltage by monitoring the feedback circuit.
Conditions for Setting the DTC
- HO2S2 heater current is less than 0.025 A.
- Engine run time is greater than 30 seconds.
- Heater duty cycle commanded is greater than 0.1%.
- Max-Min commanded duty cycle is less than 0.05%.
Action Taken When the DTC Sets
- The Malfunction Indicator Lamp (MIL) will illuminate.
- The ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers.
- A history DTC is stored.
Conditions for Clearing the MIL/DTC
- The MIL will turn OFF after four 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 DTC(s) can be cleared by using the scan tool.
- Disconnecting the ECM battery feed for more than 10 seconds.
Diagnostic Aids
An intermittent may be caused by a rubbed-through wire insulation or a wire contacting the exhaust.
Check for a poor connection or a damaged harness - inspect the harness connectors for the following conditions:
- Improper mating
- Broken locks
- Improperly formed
- Damaged terminals
- Poor terminal-to-wire connection
- Damaged harness
Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
1. The On-Board Diagnostic (OBD II) System Check prompts the technician to complete some basic checks and store the Freeze Frame and Failure Records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored on the scan tool for later reference.
2. This step determines if DTC P0141 is the result of a hard failure or an intermittent condition. With the ignition ON, engine OFF, the HO2S2 voltage displayed on the scan tool should change within several minutes toward 0 or 1 V, indicating that the heater is working properly.
3. Probing terminal 1 of the HO2S2 connector verifies if voltage is available to the HO2S2 heater.
4. If voltage is available at the connector, than it becomes a good voltage source to check for a ground at terminal 4.
5. Determines if voltage is not available at the HO2S2 due to an open in the HO2S2 fuse or open ignition feed circuit. If the fuse is open, determine if it was due to a short in the ignition feed circuit before replacing the fuse.
Troubleshooting
