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Code P0161: Meaning, Symptoms, Causes, and Fixes

  • Cars Explained
  • Sara Sam
  • 4 minutes

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Of late, have you noticed increased emissions from your car? Has the OBD scanner displayed the error code P0161? Do not worry! We’ve got P0161 covered with the causes, symptoms, and methods to fix it.

What is error code P0161? 

This is a sensor heater circuit malfunction. A problem in the oxygen sensor heater circuit can lead to this error. This code can also be triggered due to faulty wiring as well. Error code P0161 indicates that the oxygen sensor is not heating up to the required levels. This causes an increase in the emission level of your car. 

What are the symptoms of error code P0161? 

Elevated emission levels are the most common symptoms of this fault. Since prolonged driving with this issue can cause internal engine damage, it is important to look out if the engine is hinting at possible damage. The most probable issues include: 

  • A switched-on Check Engine light 
  • Engine on a rough run 
  • Reduced fuel economy 
  • Elevated emissions due to increased oxygen 

What causes error code P0161? 

The problem with the heater circuit of engine bank 1’s downstream oxygen sensor results in error code P0161.  

It is the heated oxygen sensors that enable them to reach operational temperature rapidly so that they can offer feedback to the powertrain control module as soon as possible. Sensor two monitors the air-fuel ratio expelled from the catalytic converter.  

Code P0161 is triggered when the powertrain control module detects a short or high resistance in the heater circuit for the downstream heated oxygen sensor on Bank 2. The major reasons behind code P0161 are: 

  • Fault in wiring or connections 
  • Defects in the rear-most oxygen sensor 
  • Sensor contamination 
  • Either short or open ground in wiring 
  • Fault in the electrical connector of the O2 sensor 

How to diagnose error code P0161 

The following steps can be taken to diagnose this trouble code. 

  • Perform a visual inspection of the bank 2 sensor 2 oxygen sensor wiring: This will show if the wires are routed incorrectly or the damages incurred to them.  
  • Measure the resistance of the heater circuit using a multimeter: A multimeter will indicate the resistance of the sensor. Check if the readings are within the specified range, if not then the sensor could be faulty. 
  • Check the entire circuit: If the sensor is showing the correct reading, then it is necessary to check the resistance of the powertrain control module to the sensor. In case the rest of the circuit shows the specified reading then the trouble might be with the powertrain control. 

However, simply replacing the sensor while encountering error code P0161 may not always be the solution. It is important to check the wiring, and the resistance of the circuit to avoid a mistake during diagnosis.  


Is the error code P0161 serious? 

Although the P0161 trouble code is not the most serious, you should get your car inspected as soon as you notice a problem. This error code doesn’t pose any drivability issues or obvious symptoms. As a result, it might be difficult to discover and address the issue immediately. One can detect it only if the car fails an emissions test.  

How to fix a P0161 code 

Follow these steps to fix the P0161 error: 

  • Connect the OBD-2 scanner. 
  • Check for the displayed error codes. 
  • Diagnose the reason for the error without causing a failure in the downstream oxygen sensor system. 
  • See if the problem is with the power relay of the sensor or the wiring. Splicing the problematic wire or replacing the entire sensor can be done.  
  • Similarly, the issues with the resistance readings can be solved by a sensor replacement. 
  • Do a road test after you have fixed the issues. 
  • Finally, check for a clear code and the check engine light. In case the issue persists, then the issue could be with the powertrain control module.  

How much does it cost to fix error code P0161? 

The diagnosis fee could cost anywhere between $80-$160. The rest of the repairs of the oxygen sensor, exhaust leak, or catalytic converter can range between $200 and $2400. The other factors influencing the cost are the car model, engine type, and the time required. 


How to avoid error code P0161 

There are a few steps that can be taken to avoid this error.  

  • Periodic maintenance of the sensor. 
  • Splice the damaged wires if any. 
  • Clean the sensors with gasoline. 
  • Replace the sensors after every 10,000 miles.  


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