P0161 OBD-II Trouble Code: HO2S Heater Circuit Malfunction (Bank 2 Sensor 2)

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Cost of diagnosing the P0161 code

P0161 is a diagnostic trouble code (DTC) for "HO2S Heater Circuit Malfunction (Bank 2 Sensor 2)". This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light diagnostic. Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $20.00 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.

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P0161 trouble code definition

The P0161 trouble code identifies that there is a problem with the heater control circuit in the bank 2 sensor 2 oxygen sensor.

What the P0161 code means

This code means that the bank 2 sensor 2 oxygen sensor is not warming up properly due a problem in the oxygen sensor heater circuit. Vehicle emissions could be increased due to this problem.

What causes the P0161 code?

The P0161 trouble code is caused by an incorrect amount of resistance in the heater circuit. The powertrain control module constantly monitors the resistance of this circuit. When resistance is out of specifications with this trouble code set.

What are the symptoms of the P0161 code?

The only symptom of this code is that emissions coming from the vehicle could increase due to the oxygen sensor taking longer to reach it’s operating temperature. This increase in emissions is what causes the Check Engine Light to come on so that the vehicle can be repaired as soon as possible.

How does a mechanic diagnose the P0161 code?

  • The first step in diagnostics for a P0161 trouble code is to perform a visual inspection of the wiring for the bank 2 sensor 2 oxygen sensor.

  • Many times this code can be set due to wires being damaged by being routed incorrectly or by road hazards.

  • If no problems are found during the visual inspection the next step is to use a multimeter to measure the resistance of the heater circuit in the oxygen sensor itself. The service manual for your vehicle has a resistance specification for a good sensor.

  • If the resistance of the sensor is not in specification, then the sensor is faulty and must be replaced.

  • If the sensor checks out okay, then we must check the resistance of the rest of the circuit from powertrain control module to the connector of the bank 2 sensor 2 oxygen sensor. A normal reading for wiring is less than half an ohm.

  • If the rest of the wiring is found to be good, then the likely culprit is the powertrain control module itself.

Common mistakes when diagnosing the P0161 code

The most common mistake is not performing any diagnostics at all and simply replacing the bank 2 sensor 2 oxygen sensor. The vast majority of the time, the sensor is the problem. However, from time to time there can be an issue with the wiring harness being damaged in some way.

How serious is the P0161 code?

The P0161 trouble code is not the most serious of fault codes. There are no drivability concerns related to this trouble code. The only issue is that having this trouble code stored in the powertrain control module will cause you to fail an emissions test in most areas.

What repairs can fix the P0161 code?

Need help with a P0161 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

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Jason was on time, friendly, explained everything he was doing and let me know the other services available, so when Jason comes back to install the new part I am having the oil changed too.

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BMW X3 - Check Engine Light is on - Moreno Valley, California
The mechanic arrived on time, completed the work, which was replacement of an oxygen sensor, in a timely and professional manner.


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