What does the P0161 OBD-II code mean?

The P0161 code triggers when the powertrain control module (PCM) registers an issue with the heater control circuit in the oxygen sensor bank 2, sensor 2. Effectively, the bank 2, sensor 2 oxygen sensor (HO2S) is not heating up adequately, which is being caused by a problem in the oxygen sensor heater circuit. 

How serious is the P0161 code?

This particular diagnostic code’s severity is only considered moderate, and there are no drivability issues related to this fault code. However, getting the issue resolved as soon as possible remains desirable as the P0161 trouble code will likely cause an increase in vehicle emissions that will result in an emissions test failure. The problem may also generate internal engine damage if the car continues to be driven.

What are the common symptoms of a P0161 trouble code?

Symptoms of the P0161 OBD-II code are minimal. However, you can expect the following symptoms:

  • Check engine light illuminates
  • Increased emissions
  • Decreased fuel economy

What are the causes of a P0161 diagnostic code?

The most common causes for the P0161 trouble code triggering are:

  • Faulty oxygen sensor
  • Defective wiring or connections
  • Short or open ground in the wiring

How to diagnose a P0161 OBD-II code?

The simplest way to diagnose an OBD-II fault code is to book a diagnostic check with a trusted garage or mechanic or use an OBD-II scanner if one is available to you. Following the diagnostic steps fully and  correctly is important for accurate diagnosis:

  • Make a visual inspection of the wiring and connections for the bank 2, sensor 2 oxygen sensor
  • Measure the resistance of the oxygen sensor’s heater circuit using a multimeter (resistance specification can be found in the service manual for your vehicle)
  • Check resistance for the remaining circuit from the PCM to the connector of the bank 2, sensor 2 oxygen sensor.