Air & Fuel Mixture ControlOBD2 Codes

P0161 – Meaning, Causes, Symptoms, & Fixes


What Does Code P0161 Mean?

  • P0161 definition: O2 Sensor Heater Circuit Malfunction (Bank 2 Sensor 2) – Downstream
  • Issue Severity: MODERATE– Extended driving with this code can cause internal engine damage.
  • Repair Urgency: Get this code fixed as soon as possible.
  • Diagnosis: It is important to complete the entire diagnostic process when diagnosing the P0161 code. This DTC can be triggered by a faulty oxygen sensor and/or wiring.

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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 Causes

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

P0161 Symptoms

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

How Do I Fix Code P0161?

With a P0161 code, the first step is to get it properly diagnosed to figure out what is causing the malfunction in the downstream oxygen sensor system. Using the live data function of the FIXD sensor and app allows you to read and analyze engine data to properly diagnose a P0161 code.

If the sensors are all reading correctly and you’re not comfortable further diagnosing this issue at home, we recommend finding a RepairPal-certified shop to pinpoint the problem and give an accurate estimate for repairs. 

These shops can not only help you figure out what’s going wrong before you waste time and money on the wrong parts, but they also offer a minimum 12-month, 12,000-mile warranty and stand behind all their estimates with guaranteed fair pricing.

> Find a RepairPal Certified Shop Near You

How Much Does It Cost to Fix Code P0161?

If you take your car to a shop for diagnosis, most shops will start with an hour of “diag time” (the time spent in labor diagnosing your specific issue). Depending on the shop’s labor rate, this typically costs somewhere between $75-$150. Many, if not most, shops will apply this diagnosis fee to any required repairs if you have them perform the repairs for you. From there, a shop will be able to give you an accurate estimate for repairs to fix your P0161 code.

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  • Upfront cost estimates
  • Minimum 12-month, 12,000-mile warranty
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Possible Repair Costs for P0161

When it comes to making repairs associated with the P0161 code, one or more of the below repairs may be needed to solve the underlying issue. For each possible repair, the estimated cost of repair includes the cost of the relevant parts and the cost of labor required to make the repair. 

  • Oxygen sensor: $200-$300
  • Catalytic converter: $400-$2400
  • A leak in exhaust: $100-$200 (if welded to repair)

DIY Steps to Diagnose Code P0161

If you’d like to try to fix code P0161 at home without throwing money at parts, you’ll want to follow the steps below for proper diagnosis. Complete diagnosis may require some specialized equipment beyond what the FIXD Sensor can provide, but the biggest challenge for this repair is that internal engine issues could be the root cause of this code. As such, this diagnosis and repair should not be attempted by beginner DIYers. 

DIY difficulty level: Beginner

This repair can be attempted by beginner DIYers.

Tools/parts needed (our top picks from Amazon):


Scan your vehicle to verify P0161 is the only code present. If other codes are present, they must be addressed first.


Visually check the electrical connections, wire harness, and metal tabs in terminals for any damages. If any damage is found, replace the oxygen sensor.


Consult your vehicle repair manual to locate the harness connector for the O2 sensor, and using your multimeter, check to make sure that the sensor is getting battery voltage. Disconnect the harness connector and turn the ignition to the on position (do not crank car). Test O2 sensor for proper voltage with a multimeter using the instructions from your vehicle’s repair manual. 


Consult your repair manual to find where the engine ground is located. Look for corrosion or a loose connection, and repair as necessary. 


If at this point the vehicle is still setting the same code, you may have a more serious problem with your car’s oxygen sensor system, and you should bring the vehicle to a certified shop to have further diagnostic work performed.  

Common P0161 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.

Still Need Help Fixing Code P0161?

If you’ve followed the steps above and are still experiencing issues with the oxygen sensor system and code P0161, please contact the FIXD Mechanic Hotline if you’re a FIXD Premium subscriber or find a RepairPal certified shop near you to get the right repairs at a fair price.


Lifelong automotive enthusiast with a soft spot for offroading. Wrencher turned writer, but I still love to tinker on just about anything with an engine. Dream car: tie between a ‘71 Hemi ‘Cuda and a ’91 GMC Syclone. #GirlDad #SaveTheManuals

Jeffrey N. Ross
Lifelong automotive enthusiast with a soft spot for offroading. Wrencher turned writer, but I still love to tinker on just about anything with an engine. Dream car: tie between a ‘71 Hemi ‘Cuda and a '91 GMC Syclone. #GirlDad #SaveTheManuals

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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?

      2. Just cleared code p0161 Oxygen sensor on 99 gmc 5.7 v 8 . If it stays off do you think it needs further attention. Line in Sw Ohio and just started to get colder here in late Nov. thanks and healthy regards, Harbs.

  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

  6. Hello I’m trying to see how to fix my gas gauge or about a week now it has not worked I filled my tank up but it still stays up it is empty the needle has not moved. Please help I don’t know what fuse is or if they’re even if used to the gas gauge.

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