P0141

CIRCUIT DESCRIPTION
The heated oxygen sensor (HO2S) is used for post catalyst monitoring. The 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. Ground is provided to the heater by a ground circuit. This diagnostic will only run once per ignition cycle. If the PCM detects that HO2S 2 time to become active was too long, DTC P0141 will set.

CONDITIONS FOR RUNNING THE DTC
- DTCs P0105, P0107, P0108, P0112, P0113, P0117, P0118, P0122, P0123, P0171, P0172, P0201-P0204, P0300, P0301-P0304, P0336, P0440, P0446, P0452, P0453, P0506, P0507, P0601, P0602, or P1441 are not set.
- The Ignition 1 Signal parameter is more than 10 volts.
- The Engine Run Time is less than 4.25 minutes.
- The Fuel Level Sensor parameter is more than 10 percent.
- The HO2S 2 parameter is between 395-490 mV at engine start-up.
- The ECT Sensor parameter and the IAT Sensor parameter are less than 45°C (113°F), and are within 7°C (12.6°F) of each other at engine start-up.
- The air flow calculated parameter is less than 20 g/s.

CONDITIONS FOR SETTING THE DTC
The PCM detects that the HO2S 2 parameter remains within 150 mV of the start-up voltage for a pre-determined amount of time based on ECT and air flow.

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.

TEST DESCRIPTION

Steps 1-3:

Steps 4-6:

Steps 7-11:

Steps 12-15:

The numbers below refer to the step numbers on the diagnostic table.
2. As the heater warms the O2S to operating temperature, the HO2S will output a voltage in relation 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 proper HO2S heater ignition 1 voltage and ground supply.
5. This step checks for proper PCM and signal circuit operation.