p0503 harley code

P0503 Harley Code – Causes, Symptoms and Solutions

Harley Davidson owners may have noticed the P0503 Harley code showing up in their Engine Control Module (ECM). This occurs when an irregular signal voltage is detected from the vehicle speed sensor. Learn more about this phenomenon by delving into the causes, symptoms and solutions of P503 with us.

Understanding the P0503 Harley Code

The OBD-II P0503 code is exclusive to Harley Davidson motorcycles and indicates that the ECM has identified an irregular signal voltage from the speed sensor. This sensor communicates with the ECM to regulate fuel delivery, ignition timing, and transmission shifting based on how fast your motorcycle is moving.

Causes of the P0503 Harley Code

There are several possible causes of the P0503 code, including:

  1. Faulty vehicle speed sensor
  2. Damaged wiring or connectors in the vehicle speed sensor circuit
  3. Multiple faulty wheel speed sensors/ hub bearings
  4. Broken ABS tone rings
  5. A faulty ECM
  6. Incorrect size wheels or tires
  7. A faulty instrument cluster

Symptoms of the P0503 Harley Code

When the P0503 code appears, the following symptoms may occur:

  1. Check Engine Light illumination
  2. Speedometer needle may bounce up and down
  3. Inaccurate speedometer

Fixing the P0503 Harley Code

If you’ve come across the P0503 code on your Harley Davidson, you may be at a loss for what to do. Here are some potential solutions to get you started:

  1. Carefully inspect the wiring connected to the speed sensor for any abnormalities. – If you notice any deterioration or defects, be sure to repair it or replace it accordingly.
  2. To improve your speed sensor, give it a thorough clean and consider replacing the part altogether. – With a few simple steps, this issue can likely be easily resolved.
  3. Be sure to inspect for multiple faulty wheel speed sensors and hub bearings. – If this is the problem, swap out any malfunctioning components.
  4. Carefully examine the ABS tone rings for any fractures or breaks. – If needed, switch them out with new ones.
  5. Carefully inspect the Electronic Control Module (ECM) to ensure proper functioning. – Professional diagnosis and repair may be necessary to get this problem resolved.
  6. Double-check that you’ve got the right size wheels and tires to ensure a safe, stress-free ride. – If the measurements are not accurate, switch them out for ones that fit.
  7. Diagnose the instrument cluster for any issues and replace it as needed.


Does your Harley Davidson have a P0503 code? No need to worry; there are multiple causes that could be responsible and, if you’re willing to put in the work, several ways for you to fix this issue on your own. Take time out of your day to inspect the wiring beneath the bike’s hood or consider replacing/cleaning its speed sensor – these two steps will help immensely in solving any potential issues with ease.

If the problem persists, it is prudent to get professional assistance. Remember: regular maintenance of your motorcycle can help you avoid issues like P0503 code in future.


Below are some frequently asked questions about the P0503 Harley code:

What does the P0503 Harley code mean?

An P0503 code informs us that the Electronic Control Module (ECM) has received an anomalous voltage signal from the Vehicle Speed Sensor.

What are the causes of the P0503 Harley code?

The P0503 code can be induced by several factors, such as a faulty vehicle speed sensor, weakened wiring or connectors in the speed sensor circuit, multiple malfunctioning wheel sensors/hub bearings, broken ABS tone rings, an inefficient ECM module, incorrect size wheels and tires or a defective instrument cluster.

What are the symptoms of the P0503 Harley code?

If you experience the P0503 code, it can be characterized by a lit Check Engine Light, an unsteady speedometer needle, and troubles with your vehicle’s accurate speed measurement.

How can I fix the P0503 Harley code?

When troubleshooting the P0503 code, start by inspecting the wiring connected to your speed sensor. You may need to clean or replace it, look for broken ABS tone rings, and be sure you’re using the proper size wheels and tires. If none of these solutions fix things, professional diagnosis and repair might be necessary—but this should only become a last resort.

Can I still ride my Harley with the P0503 Harley code?

Although you can still ride while the P0503 code is present, it’s important to be mindful of potential risks. The accuracy of your speedometer and other performance aspects may become compromised if not addressed promptly, so we advise taking action right away in order to prevent any further damage or safety issues arising.

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