Air & Fuel Mixture ControlOBD2 Codes

P0161 – Meaning, Causes, Symptoms, & Fixes

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Code P0161 Definition

O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 2) – Downstream

Code P0161 Meaning

Heated oxygen sensors contain heating elements to help them get to operating temperature quickly in order to minimize the amount of time spent before they can provide feedback to the powertrain control module. Sensor two is downstream of the catalytic converter ensures the catalytic converter is operating efficiently by monitoring the air-fuel ratio coming out of the catalytic converter. Code P0161 occurs when the powertrain control module tests the downstream heated oxygen sensor’s heater circuit on Bank 2 and detects a short in the circuit or excessive resistance in the heater circuit.

P0161 Symptoms

  • Check Engine Light is on
  • Engine running rough
  • Decreased fuel economy

P0161 Causes

  • Faulty rear most oxygen sensor
  • Faulty wiring/connections
  • Short or open ground in the wiring

Code P0161 Severity – Low to Moderate


This Diagnostic Trouble Code (DTC) does not need to be attended to immediately, but this DTC could result in more costly repairs in the future.

Code P0161 Common Diagnosis Mistakes

Replacing the oxygen sensor when the issues could actually lie in the catalytic converter, wiring/connections, or an exhaust leak before the oxygen sensor.

Code P0161 Diagnosis Steps

  • Tools Needed to Diagnose:

How To Diagnose P0161

This video does a great job of outlining the diagnostic process for P0161, but we have provided an overview below:

  1. Do a road test. Clear the fault codes with your FIXD sensor and drive around to verify a failure.
    1. If the Check Engine Light comes back on continue to Step 2
  2. Check that the O2 sensor is getting battery voltage by using your multimeter.
    1. Consult your vehicle repair manual to locate the harness connector for the O2 sensor
    2. Disconnect the harness connector and turn the ignition to the on position (do not crank car)
    3. Test O2 sensor for proper voltage with a multimeter using the instructions from your vehicle’s repair manual.
  3. Visually check the electrical connections, wire harness, and metal tabs in terminals for any damages
    1. Damages found? Replace O2 Sensor – Clear code
    2. No damage? Continue on to Step 4
  4. Check the engine ground – Consult your repair manual to find where the engine ground is located
    1. Corrosion? Loose connections? Remove corrosion/tighten and restart the diagnostic process

* Still having trouble finding the issue with your vehicle? Please take it to the nearest auto shop so that they may check other possible issues including the Engine Control Module (ECM).[/vc_column_text][vc_row_inner][vc_column_inner][/vc_column_inner][/vc_row_inner][/vc_column][/vc_row]

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  1. This is a wonderful service.

    1. Thanks JB! Glad we can help!

      FIXD Team

      1. I just received my FIXD and love it already! I’m a woman who knows absolutely nothing about cars!!! Got it hooked up in minutes and got my engine light off plus gave me the codes and most of all an EXPLANATION of them and what needs to be done to take care of the problem! So going to give the suggestions a try and see how it goes…I shocked myself with how easy it was, I love it!! Thank you!!

        1. That makes us so happy to hear, Cheryl! We are so glad to be able to help give the tools and confidence to learn about your car. Thank you so much for sharing your story and for using FIXD!

  2. I just got this code on my 97 Chevy Tahoe (Bank 2 Sensor 2)

    1. What was your solution? I have a 97 chevy pu with a 5.7 eng and got the same code p0161. I changed the the 92 sensor and still have the problem. Any help would be appreciated

      1. Recently scanned my 1997 Mercury mountaineer 5.0
        Every 02 sensor was infact burnt out verified by ohming out sensors replaced all four
        Still get p0161 even after replacement of all four removed entire wire harness stripped it down checked each wire individually buzzed them out line by line no breaks no shorts to engine ect an still have code issue does the mass air flow circuit work in tandum with the b2 side of 02 sensors?

  3. Love you man…awesome

  4. Thx. This was helpful.

    1. No problem Tony! Glad we could help!

  5. got this code on my 2004 mitsubishi galant gts 3.8 circuit bank 2sensor 2, how do i find the right one before i take it to a mechanic

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