P0051 – Meaning, Causes, Symptoms, & Fixes

Code P0051 Definition

HO2S Heater Control Circuit Low (Bank 2, Sensor 1)


What Does P0051 Mean?

The P0051 code is a result of the HO2S (heated oxygen sensors) incorrectly detecting the air to fuel ratio of the exhaust. This ratio is then sent to the ECM which uses this data along with comparisons to the outside air, to regulate the air to fuel ratio needed by the engine. In addition, this misreading may be the result of a bad heater element which if not operating, will trigger the P0051 code.

P0051 Symptoms*

*No noticeable adverse conditions in some cases

P0051 Cause

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

Code P0051 Severity – Moderate 

This trouble code will not prevent your vehicle from running. The most common result(s) are failure of the sensor loop, lower fuel economy, and poor vehicle operation. However, if left unsolved, this code could increase the likelihood of your vehicle running rough and cause potential damage to other components of your vehicle.

Code P0051 Common Diagnosis Mistakes

Prematurely replacing the heated oxygen sensor(s) on bank 2 before attempting to visually inspect the wiring around the oxygen sensor(s) for chafed/frayed wiring.

P0051 Diagnosis

  • Tools Needed to Diagnose:

Difficulty of Diagnosis and Repair – (1-6)

  1. Check to see if there are any other codes along with P0051 and clear your Check Engine Light with FIXD.
  2. Check the freeze frame data and fuel gauge to pinpoint the issue.
  3. Conduct a visual inspection of wiring around the heated oxygen sensor(s) for fraying or disconnection.
  4. Check the ground circuit for continuity
  5. With the engine off and the key selecting “on”, use a voltmeter to check for atleast 12 volts. If no voltage is registered, consider repairing short in heater circuit wiring.
  6. If the voltmeter registers 12 volts, consider replacing the heated oxygen sensor.

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Comments 2

Michael Brennan

April 16, 2019


Mike Brennan

May 14, 2019

I have a new O2 Sensor #1 Bank 2, I also have a knock Sensor error P0328, will the O2 sensor cause is?

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