# Tesla small drive unit limp mode



## TeZla (Feb 18, 2021)

max power and max regen slider values, lol

First up, the disclaimer, Im not an expert, im learning all this EV specific stuff at the moment as well, however I am a mechanic by trade and have been playing with ICE cars for a while. I don't claim to be right and I could in fact be waaaaaay off in my thoughts...

So, looking at the diagnostic codes and doing a little googling, a few codes seem to pop out.
It seems to think there is no BMS (DI_w092_bmsMIA) possibly a CAN network fault (DI_w094_canData) and is obviously setting itself into limp mode (DI_w062_systemLimpMode)
The last one gave me a hit on google, Anybody seen these codes? Dl_w062 Power reduced & BMS_w073 Unable to start vehicle BMS_u008
The apparent solution to their problem was to replace the HV fuse and contactors.

Seems like the CAN network isnt speaking to the BMS properly, which perhaps makes the system think the HV battery is defective or incapable of supplying the needed power, so it won't try to draw lots of power to protect itself (limp mode), Or perhaps when it starts to draw higher amperage the BMS can't give matching readings so it freaks out. An example of stupid computer stuff doing that is the ZF transmissions in some heavy vehicles, they have a speed sensor on the input and output shafts of the gearbox, if the sensor values don't match due to a bad sensor, the computer determines that the box is slipping internally even though its not and puts itself into limp mode to protect the transmission. My thought is its something similar, the motor is saying it wants (example)100A and trying to draw it, but the BMS is saying nothing so the controller freaks out thinking there is a problem inbetween somewhere and shuts everything down to prevent a high current fault that could be very damaging. That'd possibly explain the DI_w039_regenLimited code too, the BMS isnt talking so the motor can't safely feed power back into the battery under regen and so triggers a fault code.


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## TeZla (Feb 18, 2021)

The other fault codes seem normal for your setup, perhaps there is a way to turn them off? or maybe fool the controller into thinking they are there?
DI_w040_disMIA - Display missing? you don't have a display in your setup anymore, so that seems right? could also be looking for the standard Tesla dash display?
DI_w068_stwAngleMIA - no steering angle sensor found, because your van doesn't have one.
DI_w091_espMIA - your van has no electronic stability system (or extra sensory perception lol)
DI_w087_gtwMIA - not sure about this one, no idea what GTW is or could be, but its some sort of system that is missing.

Seems like these are standard Tesla fault cods, so some of it is probably looking for standard Tesla modules and systems.

If it were me, I would first check the 12v battery, swap it for another one for testing, just to rule it out because many Tesla's seems to do weird stuff when the 12v battery is faulty.
next, i'd be looking at the CAN network messages from the BMS, make sure its receiving AND transmitting all the messages it should be, check your CAN wiring and make sure you have continuity (and very low ohms) over the high and low wires, as well as clean and solid connections on the CAN line resistors on each end of the high and low wires, maybe even ensure the resistors are within the correct value range while your there.
have you contacted EV-Controls? what are their thoughts?

Looking forwards to the next vid, you guys are doing an awesome job on the build!


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## ChristopherFromDreamEV (Feb 7, 2021)

TeZla said:


> Anybody seen these codes? Dl_w062 Power reduced & BMS_w073 Unable to start vehicle BMS_u008
> The apparent solution to their problem was to replace the HV fuse and contactors.


Lets hope not :{ The battery pack is currently sealed. In retrospect it may have been better to do a non-sealing fit & test. Then following a successful test, drop it and seal the pack.



TeZla said:


> (or extra sensory perception lol)


Yet... Cough. 



TeZla said:


> Seems like these are standard Tesla fault cods, so some of it is probably looking for standard Tesla modules and systems.


My thoughts exactly... I was kinda under the impression that this controller would navigate the "expected missing component" scenario that EV conversions are going to encounter. So logically most of these errors can be ignored, Its just that last one



TeZla said:


> If it were me, I would first check the 12v battery, swap it for another one for testing, just to rule it out because many Tesla's seems to do weird stuff when the 12v battery is faulty.
> next, i'd be looking at the CAN network messages from the BMS, make sure its receiving AND transmitting all the messages it should be, check your CAN wiring and make sure you have continuity (and very low ohms) over the high and low wires, as well as clean and solid connections on the CAN line resistors on each end of the high and low wires, maybe even ensure the resistors are within the correct value range while your there.


Solid items to check!


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## ChristopherFromDreamEV (Feb 7, 2021)

TeZla said:


> have you contacted EV-Controls? what are their thoughts?


We have been in contact. They sold us the controller directly. No questions asked. Upon the issue arising we started a thread, It was determined that something had to be flashed (at this point I am not sure if we are updating the software on the controller, or the firmware on the drive unit)

So now we are in the process of trying to get a successful flash. Something is not going quite right in the process...
We tried a couple of times and decided to set up meeting for later in the week. 

Next debugging steps are the physical CAN network. Direct advice from support:
"In the meantime, make sure you have nothing else connected to the CAN bus, and you have 12V power on pin 13 of the inverter and double check the rest of the wiring."

So, now we check things.


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## ChristopherFromDreamEV (Feb 7, 2021)

TeZla said:


> Looking forwards to the next vid, you guys are doing an awesome job on the build!


Thanks dude. I am stoked that you like our videos!


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## ChristopherFromDreamEV (Feb 7, 2021)

Got off with EV controls support. There was a few issues. One being that it needed to be flashed, (we worked through that together) The second being that the T2C has an integrated 120 ohm resistor, and our three in the system prevented good communication and flashing. And the third issue is that this newer version requires a coolant pump system to prevent the system from going into limp mode. We flashed the system and get full power for a brief second, then limp mode. I am assured that a pump will fix the system


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## TeZla (Feb 18, 2021)

good news! You'll be driving at full power in no time!


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