p0051 harley code

P0051 Harley Code – Causes, Symptoms, and How to Fix it

Don’t fret if you’ve just installed a new exhaust system on your Harley Davidson and now find yourself experiencing the P0051 Harley code on the check engine light. This is all too typical, but thankfully fixable with some basic steps. In this article, we’ll analyze why it’s happening, what its symptoms are, and how to rectify it.

What is the P0051 Harley code?

The P0051 Harley code is a warning that something has gone awry with bank 2, sensor 1 of the heated oxygen sensor (HO2S) circuit. Bank 2 is on the side of the engine devoid of cylinder number one and Sensor 1 resides upstream prior to your catalytic converter.

Causes of P0051 Harley code

Your Harley Davidson may throw a P0051 Harley code for several reasons, such as:

  1. Frayed heater circuit wiring/connectors: The wiring or connectors that link the sensor to the engine’s control module may become damaged, resulting in an interruption of communication.
  2. Faulty heater circuit fuse: The heater circuit’s fuse may have blown, thereby causing the sensor to fail.
  3. Faulty heated oxygen sensor: As time passes, the oxygen sensor may eventually deteriorate in performance and cease to work correctly.
  4. Malfunctioning PCM/ECM: If the engine control module is not performing optimally, it may be unable to interpret signals from the oxygen sensor.

Symptoms of P0051 Harley code

Symptomatically, the P0051 Harley code may produce a few warning signs, such as:

  1. Check engine light: When you observe the check engine light illuminated on your dashboard, it’s a sign of an issue with the oxygen sensor in your engine.
  2. Vehicle runs rough: You could detect a drop in power and acceleration, while the engine may not be running optimally.
  3. Lower fuel economy: The engine could guzzle more fuel than expected, resulting in a dip of your vehicle’s fuel economy.

How to Fix the P0051 Harley code

If you are familiar with the signs listed above and believe that P0051 code is causing them, then here some strategies to help you get your car back on track.

Step 1: Replace the Oxygen Sensor

To begin resolving the P0051 Harley code, start by replacing the oxygen sensor. Fortunately, this is a straightforward process which you can handle at home with minimal tools. Identify and detach the upstream sensor located on the side of your engine that’s free from cylinder one; then mount in its place a new sensor followed by properly reconnecting both wires.

Step 2: Inspect O2 Sensors and Wiring

If the oxygen sensor replacement does not do the trick, it’s time to take a look at its wiring for any signs of fraying or disconnection. Furthermore, ensure that there is good continuity on the ground side of the O2 sensor’s heater circuit. When you’re finished with this step and no longer have poor continuity to ground, repair your wiring accordingly.

Step 3: Check Oxygen Sensor(s) with Multimeter

If the engine is off, and the key is “on,” check for approximately 12 volts in the O2 sensor heater with a voltmeter. In case of no voltage, inspect if there’s a fuse issue–if not then look into repairing any short/open circuit wiring that might be present. If there’s low voltage instead, examine for high resistance within its wiring; otherwise consider replacing your heated oxygen sensor when you measure up to 12 volts on your voltmeter.

Step 4: Apply Anti-Seize to O2 Connector Threads

To prevent corrosion and ensure future easily of removal, apply a small amount of anti-seize to the O2 connector threads after replacing your oxygen sensor. However, be mindful not to get any on the probes as this can lead to sensor malfunctions.

Step 5: Take it to the Dealer

If you have exhausted all other options, it could be time to take your motorcycle to a dealer for the expert diagnostic tools and know-how needed to diagnose and repair P0051 Harley code. They will provide reliable service that is sure to get you back on the road again in no time.

Will it be covered under warranty?

If you have an unexpired warranty on your Harley Davidson, the repairs for P0051 Harley code may be covered. Ensure to contact your dealer and verify this. Additionally, bear in mind that if any aftermarket parts are installed into your motorcycle, the warranty could be rendered null and void.

Concludin The P0051 Harley code

Ultimately, the P0051 Harley code is a common malfunction that can be quickly resolved by either replacing your oxygen sensor or repairing its wiring. To avoid such troubles altogether, it’s wise to make sure you routinely service your motorcycle.

If all of your attempts to fix the issue prove fruitless, it is probably best to take your motorcycle over to a professional. It’s always important to heed the manufacturer’s recommendations and consult with an expert if you aren’t certain about repairing or servicing it yourself.


Below are some frequently asked questions related to the P0051 Harley code:

What is the P0051 code, and what does it mean?

An illuminated P0051 code on your dashboard indicates an issue with the heated oxygen sensor (HO2S) in Bank 2, Sensor 1. This specific O2 sensor monitors and measures the amount of oxygen contained within exhaust gases from your engine. If this fails to accurately measure and regulate fuel-to-air ratios correctly, it could potentially cause considerable damage to other components or systems throughout your vehicle.

What causes the P0051 code on a Harley Davidson?

The P0051 code can arise from several issues, including frayed heater circuit wiring/connectors, a defective heater circuit fuse, an impaired heated oxygen sensor or even a malfunctioning PCM/ECM.

What are the symptoms of the P0051 code on a Harley Davidson?

A P0051 code can manifest with a few telltale signs, such as an illuminated check engine light, diminished fuel economy and erratic vehicle performance.

Can I fix the P0051 code myself?

If you are apt in the ways of mechanics, then you can solve the P0051 code yourself simply by replacing or repairing necessary wiring to your oxygen sensor. Nevertheless, if you do not feel secure enough with your own skillset it is advised that you seek counsel from a professional mechanic.

Will the P0051 code be covered under warranty?

If your Harley Davidson is still under warranty, the repairs for the P0051 code may be fully covered – it’s imperative to check with your dealer though.

How do I prevent the P0051 code from occurring?

To help prevent the dreaded P0051 code from occurring, make sure to keep up on your motorcycle’s maintenance needs. That includes regularly checking and replacing any oxygen sensors that are needed. Furthermore, abstain from using aftermarket parts which may not be compatible with your bike for added protection against these kinds of issues.

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