Error 21 - motor won't move on Bafang BBSHD

I seem to be very lucky with my BBSHD. On my first ride I lost the speed sensor. Had error 21 but could at least drive. After just one or two months the controller gave up. Now I finally got the repaired controller back from china and guess what? I'm still getting error 21 which is no wonder because I have no speed sensor attached. But with the new / repaired controller it instantly refuses to work with error 21.

I'd like to ride it without the display so I thought I'd ask if there is a way to ride it without the speed sensor? I thought shorting something on the speed sensor connector or flashing the controller. I don't like to buy and install a new speed sensor just to get it to work because I anyway won't see the speed if there is no display attached...

I don't know. Maybe they have flashed a new firmware (V1.4) on the controller or something. It's strange that it refuses to work with error 21.

I appreciate any help!

OK guys, I solved it for now with a custom reed sensor. I had bought some brake sensors for hydraulic brakes but am not using them because they're very shitty. They just produce error 30 when braking and sometimes it just stays there Since it works with magnets I thought it'll be a reed sensor so I gave it a try. I cutted the wire and mounted it to the speed sensor connector and it works

Still interested in a solution without any sensor though.

I'm having this exact same problem. Just bought a BBSHD... my first HD after two bbs02 builds and I'm pretty dismayed that I can't run without the sensor like I could on the previous generation.

I've been struggling to make this work all evening. Glad to know I'm not alone.
I'll post up if I find a solution.

ChickenSashimi said:

I'm having this exact same problem. Just bought a BBSHD... my first HD after two bbs02 builds and I'm pretty dismayed that I can't run without the sensor like I could on the previous generation.

I've been struggling to make this work all evening. Glad to know I'm not alone.
I'll post up if I find a solution.

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Oh boy, here I am - same story. I guess I got into this game late, because all the latest improvements are just messing me up over here. I want to run without any display, and really want to get rid of the magnet and speed sensor for a clean bike, sterile. So, are we out of luck? No fix yet? You guys still using your displays then too? Or will it run without the display, just have to still have the speed sensor hooked up? :|

Exactly as you said. Running no display, but still have to have the speed sensor on. Forever unclean!

This is the only discussion I've seen that so specifically discusses our issues, so if there's any new developments, I'm hoping to hear about it here... But I haven't actively seeked out a solution since my last post.

Please update this thread if you find a solve. I'll be sure to do the same.

If you prefer, you could make a bit of electronics with a 555 timer and a transistor, and handful of resistors and caps, which will probably all fit inside the motor/controller casing, that simply continuously sends a string of pulses to the speed sensor input the whole time the system is powered on.

You just have to set the timer chip to the same number of pulses per minute that you'd get if you were riding "normally" (so you don't want it too fast so it doesn't trigger any speed limits, and it might also "time out" if you set it too slow).

Lots of websites out there on how to use a 555 timer chip to build stuff from; pretty easy for even beginners at electronics.

Some displays allow disabling auto-shutoff in the settings if you want to see if you can get the unit to function in spite of the error 21.

TommyCat said:

Some displays allow disabling auto-shutoff in the settings if you want to see if you can get the unit to function in spite of the error 21.

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Yup, I read some posts that said just to go into the display settings and turn off the auto-power-down feature (it was set to turn off after five minutes from LUNA). It didn't work. I set it to never auto-turn off, but after about 30 seconds of running the motor without the speed sensor, it locks me out... That fix doesn't work anymore with the latest firmware or whatever... Just like how they come set for the PAS to override the throttle now...