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P0161 Code – What Does It Mean & How To Fix It

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.


The definition of trouble code P0161 HO2S Heater Circuit Malfunction (Bank 2 Sensor 2). 


This code means that the bank 2 sensor 2 oxygen sensor is not warming up properly. This is caused by a problem in the oxygen sensor heater circuit. With this particular trouble code, vehicle emissions could be elevated until this is fixed or corrected.


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. This trouble code occurs when the resistance in the heater circuit is outside of the operating specifications that it should be at. 


The only symptom of this code is that vehicle emissions are going to increase due to the oxygen. This is caused by the sensor taking a longer time to reach its operating temperature. The increase in emissions causes the check engine light to come on so that the vehicle can be repaired as soon as possible.


There are several steps that your mechanic or technician will need to take in order to properly diagnose a P0161 trouble 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 will be set due to damaged wiring. This can be caused by either the wiring being routed incorrectly or by road hazards that caused damage to the wiring.
  • 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. Refer to your vehicle’s service manual to check for the resistance specification for a good, working sensor.
  • If the resistance of the sensor is not within specifications, then you can determine that the sensor is faulty and that it should be replaced.
  • If the sensor checks out and appears to be working, you need to check the resistance throughout the rest of the circuit, from powertrain control module to the connector of the bank 2 sensor 2 oxygen sensor. Keep in mind that a normal reading for wiring is less than half an ohm.
  • If the rest of the wiring checks out and appears to be working properly, then the likely culprit is the powertrain control module itself.

Common mistakes

If you follow the above steps for diagnosis, it will minimize the chances of running into a problem while you are confirming a P0161 trouble code. However, there are some common mistakes that you should be aware of before you start trying to diagnose and fix this 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 that you are dealing with a P0161 trouble code, the sensor tends to be the problem that caused it. However, it is possible that there can be an issue with damage to the wiring harness that can cause this trouble code to occur.

How serious is this?

The P0161 trouble code is not the most serious of trouble codes, but that doesn’t mean that you should not have this trouble code investigated and diagnosed as soon as you realize there is an issue with the vehicle. There are no drivability concerns or overtly noticeable symptoms related to this trouble code, which can make it difficult to spot and diagnose. 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. If the vehicle does fail an emissions test, this could be a sign that a P0161 trouble code could be the culprit. 

What repairs can fix the code?

There are a couple of simple fixes that can be used to correct a P0161 trouble code: 

  • Replacing the bank 2 sensor 2 oxygen sensor
  • Repairing the wiring in the heater circuit.

Related codes

None listed.


Though a P0161 trouble code will not directly cause a drivability issue, it will affect the emissions of the vehicle. If the vehicle cannot pass an emissions test, this could be confirmation that a P0161 trouble code could be triggering it. Be sure to follow the step-by-step processes for diagnosing and repairing this problem, after you confirm a P0161 trouble code.

P0161 Code – What Does It Mean & How To Fix It