Bafang M620 No PAS

[sheffy]

My friend has bought a Bafang M620 bike which isn't working properly and looking if anyone can help.

• It has no PAS at all
• The throttle only seems to turn the motor slowly and the same in all power modes.
• The motor is jerky if you push the bike backwards
• It has got an error 30H on the display (communication fault)
• It doesn't show any speed on the display
• Walk assist shows on the display but doesn't turn the motor

So far I have systematically removed connectors one by one but none have removed the error code.

I have noticed that the main wiring harness has been squished at some point in time and the outer cable is slightly damaged. The speed sensor has also been pinched against the frame and the black wire is exposed.

I have a brand new motor, screen and wiring harness etc but I am not sure of the best approach as I don't want my motor to get fried.

Any help is much appreciated.

 

[TPEHAK]

If display shows communication error then no matter what assist level you set on the display it will not change the assist level on the controller and therefore PAS will not work.

I would connect your good wiring to that motor and display. I doubt you can get the wiring fried doing so, but if the new wiring makes it works then the wiring is the issue.

 

[sheffy]

If display shows communication error then no matter what assist level you set on the display it will not change the assist level on the controller and therefore PAS will not work.

I would connect your good wiring to that motor and display. I doubt you can get the wiring fried doing so, but if the new wiring makes it works then the wiring is the issue.

Good to know that the communication error overrides the PAS level, thanks!

I'll plug in my harness and speed sensor etc tomorrow and update.

 

[sheffy]

I've only got the motor and battery. Is there anyway I can hook the reention Dorado + to the motor without the frame?

 

[TPEHAK]

Communication error does not override the PAS level, communication error means there is no communication between the display and the controller and if there is no communication you obviously can not control the PAS level on the controller from the display.

If you can unmount the original motor from the frame and expose the wiring harness connectors from the frame and those connectors can reach the connectors on your new motor and you can connect your battery then you can connect it without the frame and check if the communication error is gone. If the error is gone then the controller in the original motor is probably bad (or the wiring inside the original motor is bad). If the error still exists then the problem could be the external wiring harness or the display.

Can you damage your motor controller doing so? You can in case if the wiring harness damaged the way a high voltage wire is shortened on a low voltage wire or on a signal wire. To prevent such scenario you can ring the wiring harness with a multimeter.

If you want to ring the harness you probably need the harness schematic to see which pins of the harness connectors should not be shortened and which pins should be shortened.

If this is UART harness you can find the Bafang M620 UART harness schematic in the INNOTRACE X1 controller KiCAD files in the Brain board schematic.

Archon X1 Programming Thread (questions and experiences)

Hello, did you try to contact Krasnodar first for assistance? I would contact him first. Maybe ask him when he is planning to make the online server available again (he promised to make it available soon some time ago). If he does not respond here is the link for the bypassed tool with advanced...

forums.electricbikereview.com

If this is CANbus harness you can find the Bafang M620 CAN harness schematic in the INNOTRACE M620 CAN Simple controller KiCAD files

VESC based INNOTRACE M620 Simple motor controller

The archive with the current versions of the motor controller files (KiCAD version 10.0.5), Gerber files, BOM file, components placement file, CAD files and firmware files can be downloaded here (updated on 2026-08-14)...

endless-sphere.com

 

[sheffy]

Thanks for that.

Ive removed my friends motor and battery for troubleshooting. He has the frame and will be replacing the bushes on the shock and linkage whilst I try and diagnose the error.

I've put together some alligator clips/ wires to connect my friends battery and motor to my new wiring harness and a new screen. I'll bench test it tomorrow.

 

[sheffy]

Connected my harness to my friends motor and battery and it appears to be working.

It is reading 0% battery but I've checked and it is reading only 42v (48v battery) so I've put the battery on charge.

 

[TPEHAK]

I know Bafang displays have battery settings in advanced menu, maybe you need to check that thing.

If the is no communication error when you connect your motor then maybe the problem is in the motor controller.

 

[sheffy]

My motor is brand new, I've only been trying to fix his as he bought it knowing it had a fault. It looks like it is now fixed and ready to go back on his frame.

 

[TPEHAK]

What you mean fixed? You just reconnected the wiring to his motor and the error is gone?

 

[sheffy]

I used my brand new harness to replace his harness which had visible damage (a pinch mark) and it is now working. It is out of the bike on a bench so I've only connected the battery to the motor and a display.

He can have my new cable and I'll buy a 1T2 cable instead.