Fantic Error Codes: The Complete Guide to Diagnosing and Resolving Them

There’s nothing more frustrating than being ready to hit the trail on your awesome electric mountain bike, only to come face-to-face with a flashing code on your display. At Upway, we regularly see beautiful refurbished e-bikes from premium brands like Fantic. These are sturdy machines, but like any modern electronic device, their systems can sometimes act up. The pedal assist cuts out suddenly, and there you are, faced with a cryptic number that means nothing to you.

What is your Fantic trying to tell you, and more importantly, how can you fix the problem so you can get back on the trails as soon as possible? In this article, we’ll dive into the most common Fantic error codes, find out why they’re unique, and I’ll draw your attention to a major pitfall involving the charger that could cost you hundreds of euros.

Why does Fantic have its own error codes?

Many of Fantic's premium e-MTBs, such as the Integra series, are powered by powerful Brose motors. You might expect to find a simple list of "Brose error codes" available online—but things aren't quite that simple.

Unlike competitors such as Bosch or Shimano, Brose does not offer a complete, closed-system solution (motor, display, and battery). This gives bike manufacturers the freedom to develop their own displays, software, and batteries to pair with the Brose motor. Since Fantic designs these components in-house, there is no standardized Brose diagnostic system. You therefore absolutely need the Fantic-specific codes to understand what’s going on. To learn more about how different e-bike motors work, check out our dedicated guide.

The Most Common Fantic Error Codes (and How to Fix Them)

When an error code appears on your Fantic, take it seriously. These messages indicate issues with the pedelec system that could compromise safe operation. Stop riding and refer to the common error codes listed below.

Error codes 10 & 12: Low or dead battery

These codes indicate that the battery pack’s charge level is low or even zero. Solution: Simply connect the battery to the original charger to fully recharge it. If you’re concerned about your range, our article on electric bike range will provide you with some useful tips.

Error Code 11: Load level too high

It may seem counterintuitive, but the system can detect a battery voltage that is too high. Solution: Turn the system off completely and restart it using the T4 button on your control panel. If the error persists, contact your Upway dealer Upway a bicycle specialist.

Error Code 20: Electrical Measurement Failure

An anomaly has been detected in the electrical system readings. Solution: This is often a temporary software glitch. Turn off the bike and restart it using the T4 button.

Error Code 21: Faulty temperature sensor

The system can no longer read the temperature correctly. Solution: The golden rule of IT applies here as well: “Have you tried turning it off and on again?” Restart the system using the T4 button. If that doesn’t work, you’ll need to have a technician take a look.

Error Code 24: Internal voltage out of range

The internal voltages do not match the values expected by the system. Solution: Recharge the battery pack using the original Fantic charger. See our guide on e-bike battery issues for further troubleshooting.

The Dangerous Trap of the Fantic Battery (A Costly Mistake!)

Ironically, one of the most vulnerable parts of Fantic e-bikes (such as the Integra 180) is one of their most practical features: the Rosenberger magnetic connector on the charger.

Because it’s magnetic, this connector quickly picks up dirt, bolts, or small metal washers lying on your garage floor. If you plug in the charger without first inspecting the connector, this small piece of metal will immediately cause a short circuit in the BMS (Battery Management System). Another way to accidentally cause a short circuit is to clean the connector with a damp toothbrush.

The result is a complete system shutdown: the battery no longer recognizes the charger. Fantic batteries use a highly customized BMS, with specific data cables that communicate directly with the motor and the display. It is therefore impossible to bypass or replace this BMS with a cheap aftermarket model—communication with the drive system will be lost. Always make sure the magnetic connector is spotlessly clean before each charge. To learn how to reset your e-bike battery if you encounter a problem, check out our comprehensive guide.

Extending the Life of Your Fantic Battery

At Upway, we work with batteries every day: prevention is better than cure. Here's how to keep your Fantic battery pack in top condition.

• The 20–80% rule: If you’re storing your bike for an extended period (such as during the winter), never leave the battery at 100% or completely drained (0%). From a chemical standpoint, a charge level of 50–60% is ideal for storage to prevent degradation.
• Avoid extreme cold: lithium-ion cells don't like freezing temperatures. Bring your battery indoors in the winter. And never charge a battery while it's still cold: let it warm up to room temperature for at least an hour before plugging it in.
• Moisture is the enemy: never use a pressure washer near the motor, the display, or the charging ports. Pressurized water seeps under the rubber seals and causes corrosion, which, months later, leads to unexplained error codes.

Are you looking for a refurbished Fantic e-bike? Check out our selection, which has been tested and certified by our technicians. Would you also like to compare MTB options before making a decision? Our guide to choosing an MTB will walk you through the process step by step.

Summary Table: Fantic Error Codes

FAQ — 5 Frequently Asked Questions About Fantic E-Bikes

1. What does error code 21 mean on my Fantic?

Code 21 indicates that the electrical system's temperature sensor is faulty or is providing an incorrect reading. You can often resolve this by restarting the system using the T4 button on your control panel.

2. Why do Fantic bikes equipped with a Brose motor have specific codes?

Unlike other brands, Brose does not offer a closed, all-in-one system (motor + battery + display). Manufacturers such as Fantic design their own electronic components, resulting in a brand-specific error diagnosis system.

3. Can I replace the BMS on my Fantic myself?

No, this is strongly discouraged. Fantic uses a highly customized BMS with specific cables and processors that must communicate with the drive system. A standard aftermarket BMS will not replicate this communication, and your bike will remain inoperable.

4. How do I restart the display on my Fantic MTB ?

Perform a full restart by turning off the system, then turning it back on using the T4 button on your control panel. If that doesn't work, try turning off the bike for 10 seconds, then removing and reinserting the battery.

5. How can I prevent a short circuit when charging my Fantic?

Inspect the Rosenberger connector before each charge. Since it is magnetic, it may pick up washers or bolts from the floor. Never clean it with a liquid or a damp brush. Even the smallest foreign object between the connector and the battery can permanently damage your BMS.

Written by: Hanna Stevens | Published on: June 29, 2026 | 5-minute read

About the Author: Hanna Stevens

Hanna is a cycling enthusiast who loves discovering new routes and sharing her experiences to inspire more people to get around by bike.