P0165 OBD-II Trouble Code: O2 Sensor Circuit Slow Response (Bank 2, Sensor 3)

Check Engine Light

P0165 code definition

O2 Sensor Circuit Slow Response Bank 2, Sensor 3

What the P0165 code means

The P0165 code means that the powertrain control module is not getting a normal response from the O2 sensor.

O2 sensors calculate the level of oxygen that passes by them. The signal that the O2 sensor sends to the powertrain control module is in the form of a reference voltage. If this voltage becomes lower than a specified range given by the manufacturer due to more resistance in the circuit, this code can appear.

This code can also be stored in the powertrain control module if the voltage reading coming from the O2 sensor remains the same for an extended period of time indicating a slow response.

What are the causes of the P0165 code?

  • A faulty oxygen sensor
  • A damaged connector to the oxygen sensor
  • Damaged wiring in the O2 sensor system
  • A faulty powertrain control module
  • Anything that could affect the air fuel ratio i.e. vacuum leak

What are the symptoms of the P0165 code?

Other than the obvious Check Engine Light, symptoms of the P0165 code could include decreased fuel mileage, and the engine may run rough depending on the cause of the code. This code may also be associated with other codes.

How does a mechanic diagnose the P0165 code?

A mechanic may diagnose the P0165 code by lifting the vehicle up and giving the oxygen sensors a visual inspection. This inspection would include checking the condition of the oxygen sensors and the electrical wiring and connectors associated with them.

If any problems are found during this visual inspection, the oxygen sensor(s) will likely require replacement. If no problems are found in this area, the visual inspection would continue upwards to the engine bay.

The engine would be checked for obvious vacuum leaks visually and possibly confirmed with a smoke test. If no vacuum leaks are found, no issues with the oxygen sensors are found, and no electrical issues are found, the problem likely lies within the powertrain control module.

Common mistakes when diagnosing the P0165 code

The easiest mistake that could be made when diagnosing the P0165 code would be to just replace the oxygen sensor without testing them with the manufacturer’s recommended procedure.

Many people think that, just because a certain part is mentioned in a diagnostic trouble code, that this automatically means the part is going bad. While this could be the case, the code could also mean that another related component is at fault. It is always good to follow procedures when diagnosing automotive problems.

How serious is the P0165 code?

The P0165 code is not so serious at first, but can become worse as time goes by. If your engine is running lean or rich for a long period of time, the fuel efficiency of your vehicle will decrease causing you to spend more money to drive your vehicle.

Also, if the air/fuel ratio is incorrect for a long period of time, the catalytic converters may be damaged due to unburned fuel from the engine burning off inside them.

A problem that started as a possible oxygen sensor replacement could turn into replacing half of the exhaust system. If this code appears in your vehicle’s memory, it is wise to have the issue diagnosed as soon as possible.

What repairs can fix the P0165 code?

Additional comments regarding the P0165 code

If this code has existed for some time in your vehicle’s memory, you may check under your vehicle from time to time to see the color of your catalytic converters after driving. If any part of the exhaust appears to be red hot after this code is saved, it’s time to stop driving the vehicle. If this happens, fuel has entered the exhaust and the next item that will be damaged is the engine. As said above, make sure to have this problem diagnosed and repaired as soon as possible in order to prevent future issues.

Need help with a P0165 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.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

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