How Do I Fix Bosch Error 503? (Solved With Pics)


The 503 error in the Bosch system is one of the most common errors on Bosch bikes. This error is specific to the speed sensor.


The reason for the appearance of the error is the inability of the speed sensor to sense the wheel roll and accordingly, the controller cannot give you a correct reading, and also the motor does not work properly.


In this post, we will explain how to solve this error and also the reasons that lead to its appearance.


The reasons why you have Bosch Error 503 on your ebike screen.

In this part, we will explain the reasons that may lead to the appearance of a 503 error on your Bosch bike.


1- Misalignment between the magnet & speed sensor.


The first and most famous reason is that the magnets on the spokes of the wheel are not opposite to the sensor correctly, and therefore during the rotation of the wheel, the sensor will not be able to sense the rotation of the wheel properly.


2- The Speed sensor is defective.


If you find the magnet is in the correct place and you still see an error 503 on the screen of the electric bike, this means that the sensor itself has a problem and you should test it

You can check out this post to learn how to test the speed sensor.


How do you test an ebike speed sensor?


3- The speed sensor needs refreshment.


There is a very small chip inside the speed sensor and sometimes this chip stops working properly all you have to do in this case is just refresh this chip.

Note: We will explain this method in detail in the next part of this post.


4-You made unusual adjustments on the ebike wheel.


If you make any adjustments to the rear wheel in order to increase the speed or for any other reason, you will most likely see an error 503 on the display of the electric bike.


Now, after we have explained the most important reasons that may lead to error 503, we will explain in the next section how to fix each of the previous reasons.


How Do I Fix Bosch Error 503?


1-  Magnet Alignment.


To solve the problem of error 503 caused by the magnet not aligning the speed sensor, follow the following steps


1- Turn the rear wheel until it reaches the spoke with the magnet.


Turn the rear wheel until it reaches the spoke with the magnet


2-Using a screw loosen the agent & realign it opposite to the speed sensor. (you should only make the distance between the magnet and the sensor 3 or 4 MM)


Using a screw loosen the agent & realign it opposite to the speed sensor.



3- turn off the bike & turn it On again & the error will disappear.


 2- Speed Sensor Refreshment.


In the event that the magnet is perfectly aligned with the sensor and does not need modification, we will move on to the next step, which is to refresh the inner chip of the sensor.

In order to do this step, you will need a strong magnet and do the following steps


1- Bring the magnet and pass it in front of the sensor in a circular shape quickly for 10 seconds

2- turn off the bike

3- Start the bike again.


3-Remove any adjustment on the rear wheel.


If you made any adjustments to the rear wheel and did the previous steps and the error still exists, the next step is to remove these adjustments and then restart the bike.

4- Speed sensor replacement.

If you did the previous steps and the error still exists, then the most likely possibility is that the sensor does not work at all and needs to be replaced.


Note: In order to change the speed sensor, you should go to an authorized dealer of Bosch bikes to change it for you, this for two reasons:

First, the bike remains in warranty, and secondly, Bosch systems have programs to reprogram the bike in the event of changing any part, and these programs are available with authorized sellers only.




As a general rule, you can fix the Bosch 503 error by realigning the magnet in front of the speed sensor or replacing the sensor.


On the other hand, you can make a refresh for the sensor using an external magnet and scroll it quickly in front of the sensor, and finally, if any adjustments are made to the rear wheel, remove them.

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