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P0051 – Meaning, Causes, Symptoms, & Fixes

P0051
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What Does Code P0051 Mean?

  • P0051 definition: HO2S Heater Control Circuit Low (Bank 2, Sensor 1)
  • 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 P0051 code. This DTC can be triggered by a faulty oxygen sensor, damaged wiring, blown fuse, or an ECM failure.

The P0051 code is a result of the bank 2 HO2S1 (pre catalytic converter heated oxygen sensor) heating element having low voltage. Heated O2 sensors have a separate heater inside the sensor to get them to operating temperature quickly. The faster your O2 sensor(s) get to operating temperature the faster the car is in a fuel-efficient and emissions friendly configuration. If this code is set, the oxygen sensor heater is not working.

P0051 Causes

  • Frayed heater circuit wiring/connectors
  • Faulty heater circuit fuse
  • Faulty heated oxygen sensor
  • Malfunctioning PCM/ECM

P0051 Symptoms*

*No noticeable adverse conditions in some cases

How Do I Fix Code P0051?

With a P0051 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 P0051 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 P0051?

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 P0051 code.

Possible Repair Costs for P0051

When it comes to making repairs associated with the P0051 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
  • Wiring repair/replacement $100-$1000

DIY Steps to Diagnose Code P0051

If you’d like to try to fix code P0051 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 for the most part, this diagnosis and repair can 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 P0051 is the only code present. If other codes are present, they must be addressed first.

STEP 2: INSPECT O2 SENSORS AND WIRING. 

Conduct a visual inspection of bank 2 pre catalytic converter oxygen sensor wiring for fraying and/or disconnection. Check the ground side of the O2 sensor’s heater circuit for continuity to ground. It should have good continuity; if it doesn’t, repair wiring.

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

With the engine off and the key “on”, use a voltmeter to check for approximately 12 volts (should be the same voltage the vehicle battery is at) on the power side of the O2 sensor heater. 

    1. If no voltage is registered, check the fuse; if the fuse is good, consider repairing short/open in heater circuit wiring.
    2. If low voltage is measured, check for high resistance in the wiring.
    3. If the voltmeter registers 12 volts, consider replacing the heated oxygen sensor.
STEP 4: 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 P0051 diagnosis mistakes

Prematurely replacing the heated oxygen sensor before attempting to visually inspect the wiring around the oxygen sensor for chafed/frayed wiring.

Still Need Help Fixing Code P0051?

If you’ve followed the steps above and are still experiencing issues with the oxygen sensor system and code P0051, 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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