P0141
CIRCUIT DESCRIPTIONThe heated oxygen sensor (HO2S) heater is a device used in order to reduce the time that the sensor takes to go active. The HO2S bank 1 sensor 2 heater helps to maintain the sensor at the proper temperature for catalyst testing, and additional adjustments to fuel trim. The HO2S heater receives power through a fused ignition circuit. The powertrain control module (PCM) turns the heater ON and OFF using a low side driver output driver module (0DM) located within the PCM.
The PCM will test the healer only after a cold start. The PCM determines a cold start based on the difference between the engine coolant temperature (ECT) at the last key OFF, and the ECT at the current key ON. When the HO2S voltage indicates a sufficiently active sensor, the PCM looks at how much time has elapsed since start-up. If the PCM determines that too much time was required for the sensor to become active, this DTC will set. The amount of time for the sensor to reach operating temperature is based on the ECT at start-up and the average mass air flow (MAF) since start-up (more air flow and/or higher start-up ECT results in a shorter time to sensor activity).
CONDITIONS FOR RUNNING THE DTC
^ DTCs P0137, P0138, or P0140 are not set.
^ The difference between ECT at last key OFF and the current key ON indicates a cold start.
^ The system voltage is between 10-18 volts.
^ The average MAF is less than 30 grams per second.
CONDITIONS FOR SETTING THE DTC
The HO2S bank 1 sensor 2 voltage remains within 150 mV of the bias voltage (approximately 450 mV) for a longer amount of time than expected. The amount of time for the sensor to reach operating temperature is based on the ECT at start-up, and the average mass air flow since start-up for a maximum time of 2500 seconds.
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
