P0141

Circuit Description
In order to control emissions, a catalytic converter is used to convert harmful emissions into harmless water vapor and carbon dioxide.

The Engine Control Module (ECM) has the ability to monitor this process by using a Heated Oxygen Sensor (HO2S). The HO2S, 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 exhaust emissions effectively. If the catalyst is functioning properly, the HO2S signal will be far less active than the signal produced by the Oxygen Sensor (O2S).

If the HO2S pigtail wiring, connector, or terminal is damaged, the entire HO2S assembly must be replaced. Do not attempt to repair the wiring, connector, or terminals. In order for the sensor to function properly, it must have a clean air reference provided to it. This clean air reference is obtained by way of the HO2S wire(s). Any attempt to repair the wires, connector, or terminals could result in the obstruction of the air reference and degrade the HO2S performance.

The ECM will check if HO2S is functioning properly by monitoring the time for HO2S sensor to become active only after a cold start and only once per ignition cycle. If the ECM determines that too much time was required for the HO2S to become active, DTC P0141 will set.

Conditions for Setting the DTC
- Start-up Engine Coolant Temperature (ECT) is less than 90 °F (32 °C).
- Start-up Intake Air Temperature (IAT) is less than 90 °F (32 °C).
- Difference between start-up ECT and IAT is less than 45 °F (7 °C).
- Ignition voltage is between 11 and 16 volts.
- Average airflow is less than 16 g/sec.
- HO2S voltage at key ON must be between 400 mV and 500 mV.
- Throttle Position (TP) sensor is less than 50%.
- DTCs P0131, P0132 and P0134 are not set.

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 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 DTC(s) can be cleared by using the scan tool.

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

Steps 1 - 7:

Steps 8 - 14:

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 to 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 HO2S 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 connector verifies if voltage is available to the HO2S heater.
4. If voltage is available at the connector, it becomes a good voltage source to check for a ground at terminal C.
5. Determines if voltage is not available at the HO2S due to an open O2 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.