BBS02 Throttle Always High (~4.9V) – Error 04 After Shorting Signal Pin

[yasjas]

Hi all,

I’m troubleshooting a throttle issue on my Bafang BBS02 750W. The bike runs fine on PAS, but the throttle does nothing (unless shorted), and I’m now consistently getting Error 04: "Throttle not returning".

Here’s what I’ve tried:
Throttle works when shorting/jumping signal + power causes the motor to spin briefly, but Error 04 is triggered immediately
Throttle replaced – (not 100% sure if 2nd throttle works)
Display shows PAS level 3 (not 0)
PAS works fine
Config tool changed throttle start/end voltages 4.8-5v
Voltage test (2 bottom pins: ~4.9V — as expected.)

Has anyone seen this exact stuck-high condition before?​

• Is this repairable at the controller level (e.g. open input trace, blown resistor)?
• Any success adding external pull-down resistor to lower the signal and avoid Error 04?
• Or is this controller replacement time? Bafang recommends it https://bafang-e.com/uploaded/errcode/202209091001382527.pdf

I have access to a multimeter, Bafang config tool, and basic soldering gear. I’d rather fix than replace if it’s realistic. Thanks in advance!

 

[docw009]

Shouldn't start be 1.x and end 4.x volts? Maybe I read you wrong when you said 4.8 and 5 volts.

From "A Hackers guide to Programming the BBS02B"

Start Voltage(x100mv): 11\11\11\11\11 – The is the throttle input starting voltage, the point at which the controller responds to input is at 1.1 volts, so set value to 11 which = 1.1 volts. As you begin to roll on the throttle the voltage moves up from zero and when it reaches 1.1v the motor begins to turn. Best to leave between 10 and 15. Too low and the display will throw an error as the motor will want to run continuously. If you change the throttle you will need to find the new lowest setting.


End Voltage(x100mV): 35\35\42\35\35 – You can set the max range to 42 which is the max input the controller accepts from throttle input 4.2v. If you set lower than this value your throttle response is not as linear or smooth as it could be. Matt suggests you set start voltage to 11 and end voltage to 4.2 for a wider range of throttle response and smoother control of motor output. If you use an aftermarket throttle you will need to test to see what voltage the hall sensor throttle is giving off at full throttle and set this number slightly lower than that voltage shown on the meter (times 10).

 

[aae34]

Yes, those are definately wrong/impossible to work with values for start/end voltage.

Should measure what the throttle gives, and use that information for configurating.