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Dreaded Error 21

Started by oldtexasdog, June 10, 2023, 09:28:57 AM

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Brand new City 5 plus took a 100 yard test ride on flat street then went to show wife and error 21?!!? E-Mailed Rad but no response so far. Did all the unplugging and re plugging to no avail. Have I got a 2000.00 brick?


It's not getting a pulse from the wheel speed sensor. On some bikes with Bfang motors, the speed sensor is by itself on a chain stay, and the magnet is on a spoke. On my two Radpower bikes, they're part of the motor assembly. I wish I knew more about them.

On my bikes, the motor connector has three big pins for power and a bunch of little pins. Maybe one of the little pins got bent over. Maybe careful straightening would let it connect.


Checked every pin connector. Still 21.


Quote from: oldtexasdog on June 11, 2023, 12:27:05 PM
Checked every pin connector. Still 21.

Darn! If the sensor were external, as it is on many brands, you could test it by waving a magnet. If it responded, you'd reposition the sensor or the spoke magnet. If it didn't, you could install a generic sensor.

Even in 2021, Radpower could take weeks to respond when I needed tech support. Good luck!


Tried calling them and keep getting the message-Were not answering phones and customer help is closed right now???!!


Well I drove 80 miles and took it into a auth. service bike shop. Nearest one :P
Now lets see what happens?


I am in the exact same situation. Bought 2 RadCity 5+ Step-Thrus ? one white, one black on June 2.

They seemed to both be working and I took my teen daughter for a spin, she was so unimpressed with the experience. Could not figure out why it was so hard... then she told me "it says 21 on the screen". The white one is now giving a persistent Error 21. I did all the unplug/replug, battery off/on, etc, etc.

It continues to flash Error 21.

I have now entered the Rad Power Bikes Customer Service Vaccum.

We have one functioning bike and my wife and I go on solitary rides.

Reading the various forums and the past few years of experience, I am sure that we will watch the summer vanish while we wait for another faulty controller to arrive.

This is so disappointing.

I am thinking of returning the bike.


Well the approved Tek I took the bike to has informed me that Rad sent him a e-mail apologizing for their customer service issues and stating that they were working on fix's. They are also sending him a new controller and covering it all under warranty. They said there would be some delay as the part was on back order. So we will see.


Well Rad sent a new controller and battery jack on bike. The Teck installed them and code 21 went away and now it's code 30!!???
Teck says the new parts are faulty and is now trying to get Rad to respond. Damn thing is brand new and I got to use it for 5 min! Now it's over a month old and past the allowed time for a return.


Still waiting on parts! Bike was delivered June 3 and worked for 1 hour.
This is how RAD treats it's warranty and customers???!!


contact your credit card company.  hopefully they are able to help.

Check out Citizen Cycle on YouTube.  He reviews several different brands. 


I think I would like to e-mail the CEO of RAD documenting my experience. Anyone have the name or e-mail?


Well RAD sent out a new controller, new wiring harness, new battery jack. Now it works! Seems there was a short in the wiring harness that fried the computer.
Hope it runs for a long time.


Just got back from a 20 mile ride and everything still working great!


Glad to hear you have a fix. I am in Error 21 hell now with my wife's white Rad City 5 Plus step thru. I paid $60 for a new wiring harness that we connected but no luck. I contacted Rad support and now they sent me an email with an invoice for a new battery mount and controller @ $200 but when I went to order it was out of stock and when I complained they said it is a supply chain issue and they hope to have the part in January 2024! Almost laughable if not so disappointing.

I am not sure what to do next. The bike is a 2021 so out of warranty but it only had a 100 miles on it.