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P0161 – Meaning, Causes, Symptoms, & Fixes

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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.

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.

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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.

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):

STEP 1: USE FIXD TO ENSURE NO OTHER ENGINE CODES ARE PRESENT.

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

STEP 2: INSPECT O2 SENSORS AND WIRING. 

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

STEP 3: CHECK OXYGEN SENSOR(S) WITH MULTIMETER.

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. 

STEP 4: CHECK THE ENGINE GROUND.

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

STEP 5: CONSULT A PROFESSIONAL.

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.

Jeffrey-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

We’re here to help you simplify car care and save, so this post may contain affiliate links to help you do just that. If you click on a link and take action, we may earn a commission. However, the analysis and opinions expressed are our own.

About the Author

Jeffrey N. Ross

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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