All,

I just got the check engine light yesterday, checked the codes and this is what I got -

P0141 HC
P0161 HC

They are both current and are the Ox Sensor Heater Circuit for Banks 1 and 2 Sensor 2-B.

Any idea what the malfunction may be? Is this the O2 sensor itself not working? Or a circuit issue? Any input is appreciated. I can't bring the car in until tomorrow earliest, so I'm curious as to what it may be.

Thanks for the input!

Jonathan

 

I was getting the P0161 code on a daily basis. The dealer said it's usually a bad wire or harness. It turned out to be the sensor. They replaced it and no more codes!

Jim

 

HC means historical and current.

DTC P0135, P0141, P0155, or P0161
Circuit Description
The powertrain control module (PCM) supplies a bias voltage of approximately 450 mV on the heated oxygen sensor (HO2S) high and low signal circuits. When you turn the ignition ON, the battery voltage is supplied to the HO2S heater. As the heater reaches the operating temperature, the HO2S voltage responds by changing from a bias voltage range to the normal operation. Typically, as the HO2S reaches the operating temperature, the HO2S voltage goes from a bias voltage to a voltage below 300 mV. Depending on the exhaust gas content, the HO2S voltage can go above 450 mV.

The PCM runs the heater test only on a cold start, depending on the cumulative air flow, and only once an ignition cycle. When you start the engine, the PCM monitors the HO2S voltage. If the HO2S voltage goes above or below the bias range threshold, the PCM determines how much time passed. If the PCM detects that the process took too much time for the HO2S to enter into normal operating range, a DTC sets. The time the process takes the HO2S to reach the operating temperature is based on the amount of air that flows into the engine.

Conditions for Running the DTC
DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0131, P0132, P0134, P0137, P0138, P0140, P0151, P0152, P0154, P0157, P0158, P0160, P0200, P0300, P0410, P0440, P0442, P0446, P0452, P0453, P1120, P1125, P1220, P1221, P1221, P1258, P1415, P1416, P1441, P1514, P1515, P1516, P1517, or P1518 are not set.
The intake air temperature (IAT) and the engine coolant temperature (ECT) are less than 50°C (122°F) and are within 8°C (14.5°F) of each other at engine start-up.
The ignition 1 signal is between 9-18 volts.
The secondary air injection (AIR) and the catalyst diagnostics are not active.
The scan tool is disconnected.
The mass air flow (MAF) is less than 18 g/s.
Conditions for Setting the DTC
The HO2S voltage remains between 300-600 mV for a predetermined amount of time, depending on the engine coolant temperature and the 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.
Diagnostic Aids

Important
Before you service the PCM and throttle actuator control (TAC) module, remove any debris from the module connector surfaces. Inspect the module connector gaskets when you diagnose or replace the modules. Ensure that the gaskets are correctly installed. The gaskets prevent contaminate intrusion into the modules.
For any test that requires probing the PCM or probing a component harness connector, use the connector test adapter kit J 35616-A . Using this kit prevents damage to the harness and component terminals. Refer to Using Connector Test Adapters in Wiring Systems.

The heater diagnostic will only run on a cold start and will run once per ignition cycle.
An oxygen supply inside the HO2S is necessary for proper operation. The HO2S wires provide the supply of oxygen. Inspect the HO2S wires and connections for breaks or contamination.


[Modified by kewlbrz, 2:55 PM 12/3/2001]

 

Kewlbrz, as always, thanks for the technical input, greatly appreciated.

:cheers:

One question though, I don't necesarily understand the following The way I am understanding, a bias is applied to correct for an offset due to the sensor being below operating temperature. The O2S is heated by the exhaust gas right? I just don't completely understand the quote above.

Its probably just a sensor or wire, but I'd love to understand it more.

Thanks!