[Solved] Error 04 on Bafang DP C07.UART / Surface 604 Shred - how to replace throttle?

[soramimo]

Hi all,

Half way through a steep uphill climb (on support level 5), my motor shut off and now I'm getting an Error 04 on my display [1].

I have a 2018 Surface Shred with a Bafang DP C07.UART display.

After searching around a bit, I found Bafang documentation on Error 04 (link) that suggests the issue is either a stuck throttle or a broken controller.

To see what's going on, I would like to disconnect or replace the throttle, however, it's not obvious to me how to do it as the cables seem to be fix (see picture [2]).

My question is - how do I disconnect the throttle? Do I need to open up the display? Will it not work at all (short of clipping the cable)?

Thank you!
Chris

P.S. I don't really think it's the throttle, but probably something got fried / overheated while going uphill - but want to test the simple things first before starting replacing things like controller or motor


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[2]

 

[amberwolf]

I don't see the full cable path from throttle to display--is there no connector between them?

If not, you would probably have to open up one of them to get access to the wiring, but if they are not simply screwed together (many waterproof things are ultrasonically welded, even if they are also screwed together), you may have to cut into the cable housing to access the wires. Re-waterproofing this is possible in several ways, depending on how picky you are about how it looks.

If it is a stuck throttle voltage, the most common issue is a broken ground, leading to a full-throttle event (because of loss of the ground reference, the signal is seen by the controller as close to or at the throttle supply voltage).

If the throttle can be disconnected, that will make a quick test for this even without measuring anything--no supply voltage and no signal means no stuck-on throttle input to the controller. If it persists, it's somewhere in the wiring or display between the controller and throttle, or at the controller itself.

 

[soramimo]

Thanks for the fast response!

I don't see a connector between the two sides (here's a picture [1] for future reference). I'll try to open the display first (unless anyone else here in the forums has a better idea) and see where that takes me.

Now, there's one more thing I should mention - I don't see the error when turning on the bike. It only starts showing when starting to pedal at the point where the engine would kick in (in fact, it does a bit of a quick push, but then immediately shuts off again in a split second). I'm guessing that's even more evidence that it's actually NOT related to the throttle, but as you said, I'd still prefer to do a quick test to make sure.

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[amberwolf]

I don't see a connector between the two sides (here's a picture [1] for future reference). I'll try to open the display first (unless anyone else here in the forums has a better idea) and see where that takes me.

I can't tell for sure, but the picture doens't appear to show a throttle, just the button pad that's part of the display.


It's more common for the throttle to be on the right side handlebar than the left, but your pictures don't show that side.

Now, there's one more thing I should mention - I don't see the error when turning on the bike. It only starts showing when starting to pedal at the point where the engine would kick in (in fact, it does a bit of a quick push, but then immediately shuts off again in a split second). I'm guessing that's even more evidence that it's actually NOT related to the throttle, but as you said, I'd still prefer to do a quick test to make sure.

If it was a real stuck throttle voltage (at least, for the type that's stuck "on"), it would happen at system poweron, and the system, if properly designed, should detect and complain about this right then, before you even attempt to use it.

So it sounds like the error code is not for the throttle, but is for some problem that is not covered by any of the built-in error codes, and is either the first or last in the list in the software (not the manual, but the actual code), so that the software looks for a matching code for the error it gets, doesn't find one, and so uses that as a default "everything else goes here" message.


Does the problem happen with the wheel offground? Or only with it on-ground with you on the bike?

Does it respond to the actual throttle, if not using the pedals at all? (either offground or on).

 

[soramimo]

I can't tell for sure, but the picture doens't appear to show a throttle, just the button pad that's part of the display.

Oh my, you're absolutely right (can't believe I missed this). It was a bit dark when I took the picture, so I went back to look closely and indeed, what I was looking at is not the throttle cable.

The throttle is next to the controller, but has a separate cable that doesn't feed into the display. In fact, after unwrapping the protective tape a bit I do see a connector (see [1]).

Sure enough disconnecting it doesn't change anything, which is as expected.

Does the problem happen with the wheel offground? Or only with it on-ground with you on the bike?

So I threw my bike up on a repair stand [2] and tried it - the error shows up on and off when pedaling, but the engine doesn't turn on at all (on the ground the engine seems to make a few short, sub-second, jerky movements).

Does it respond to the actual throttle, if not using the pedals at all? (either offground or on).

No, the throttle doesn't do anything.

The good thing is that my wife has exactly the same model, so I'm thinking to connect her hub motor to my controller or vice versa to figure out whether the problem is the controller or the engine (I'll also swap the batteries before, just to make sure it's not that).

Any ideas / suggestions welcome!

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[amberwolf]

The most likely thing given the jerkiness is a connection fault between motor and controller.

If there is no obvious visual sign of cable damage, especially at the exit from the axle for the motor cable (very common; usually from a crash or a fallover or catching on something during a ride offroad, etc), I'd first just try unplugging and replugging the connector between motor and controller once or twice to clear any oxidation on the contacts.

If nothing changes, there are other tests (lots of threads I've posted in for troubleshooting bikes have specifics on various tests for various things, if you don't want to wait for a reply to whatever new info you run across from the above).

My guess is the "throttle" error is used for *any* sensor including the hall sensors, if there's no other specific error code in the list for it.

 

[soramimo]

Here's a quick update.

I hooked up the hub motor of my bike to my wife's controller and confirmed that the motor works fine [1]. Also swapping batteries didn't change anything, so I think the most likely culprit is the bike's controller [2].

I didn't see anything wrong with the cables going in and out of the controller, so I went ahead and ordered a replacement from Surface, let's see how it goes.

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[soramimo]

Another quick update - I ordered a replacement controller from Surface 604, installed it, but the bike's still dead (in the sense that the head unit turns on, but engine won't kick in with neither throttle nor pedal assist).

Next steps, I'm planning to check the wiring (it sounds like battery, controller and hub motor are all ok). For now, I've ordered one of these "Brushless Motor Testers", but am researching too how to go about it using a Multimeter. Stay tuned .

 

[E-HP]

Another quick update - I ordered a replacement controller from Surface 604, installed it, but the bike's still dead (in the sense that the head unit turns on, but engine won't kick in with neither throttle nor pedal assist).

Next steps, I'm planning to check the wiring (it sounds like battery, controller and hub motor are all ok). For now, I've ordered one of these "Brushless Motor Testers", but am researching too how to go about it using a Multimeter. Stay tuned .

Is it the exact same controller? Will the new controller run your wife’s motor?
Did you try your wife’s throttle on your bike, with the old controller?
I would start back with your old controller. Disconnect the brake cutoffs and PAS, and use your wife’s throttle.

 

[soramimo]

Is it the exact same controller?

Yeah, it's the exact same controller, but I agree that starting back from my old controller is a good idea.

Will the new controller run your wife’s motor?

Haven't tried this yet, but good thing to check!

Did you try your wife’s throttle on your bike, with the old controller?

No, but that's a good idea too.

I would start back with your old controller. Disconnect the brake cutoffs and PAS, and use your wife’s throttle.

Thanks for the advice, will give this a shot!

The only thing left to do is figuring out which wire is which [1] since nothing is labeled (I already know which are the battery hot and neutral and the three phase wires, plus the 5 Hall sensor cables). I'm not sure yet about the rest and will try to figure it out with my multimeter, YouTube and trial and error.

Another thing [2] I did since the last update was confirming continuity from where the controller connects to the connector that goes to the motor for all 3 phases plus hall sensors (all good).

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[soramimo]

Problem solved!

After hooking up my wife's throttle, everything is working as expected (tested here [1]). The mistake I made was assuming that disconnecting my broken throttle should fix it, but that wasn't the case . Somehow, the motor won't come on at all when the throttle cable is disconnected (apparently even pedal assist won't work).

Oh well, I learned quite a bit about my bike and ended up leaving the new controller installed after all as (involuntary) proactive maintenance.

Thanks for all the help (in particular the suggested to swap in my wife's throttle, after I had already discarded it as a source of error).

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