Identifying Front vs Rear Tesla SDU Logic Boards

[nubster]

Is there any reliable way to tell whether a Tesla OEM Small Drive Unit (SDU) control board came from a Front SDU (FSDU) or a Rear SDU (RSDU)? I've collected several OEM logic boards over time and, unfortunately, lost track of which ones came from where. I know I have a mix of both FSDU and RSDU boards.

ChatGPT suggested that part number 1034827-01-E REV01 is specific to the RSDU, but when I asked for a source, it referenced a random eBay listing for an RSDU inverter—so I’m not fully confident in that answer. All of my boards have this same P/N.

Do the front and rear SDUs actually use different logic board part numbers, or are they the same? Is there a way to visually distinguish them, or would I need to power them up and sniff the CAN traffic to tell which is which?

Thanks!!!

[Slimjimmy]

That part number matches my 2017 model x front drive unit

[nubster]

That part number matches my 2017 model x front drive unit

Yeah, I’ve reached out to a few people via email as well, and they’re all saying the same thing—it seems that all (or at least many) FSDU and RSDU logic boards share the same part number. Does that mean the hardware is identical, and the difference comes down to the firmware that's flashed onto them?

[P.S.Mangelsdorf]

Yeah, I’ve reached out to a few people via email as well, and they’re all saying the same thing—it seems that all (or at least many) FSDU and RSDU logic boards share the same part number. Does that mean the hardware is identical, and the difference comes down to the firmware that's flashed onto them?

My understanding what that the front and rear SDU were basically the same, with different casings to accommodate the different locations.

[nubster]

My understanding what that the front and rear SDU were basically the same, with different casings to accommodate the different locations.

The firmware definitely differs because the RSDU units require a throttle and brake input to operate. In contrast, the FSDU can be controlled entirely via CAN when using certain aftermarket VCU/controllers. These controllers (and Tesla toolbox) detect if it's an FSDU or RSDU board, so there must be some identifying information within the CAN traffic. So I'm currently trying to figure out how to identify the boards via CAN. If anyone knows what message to look for, please kindly share!

[P.S.Mangelsdorf]

The firmware definitely differs because the RSDU units require a throttle and brake input to operate. In contrast, the FSDU can be controlled entirely via CAN when using certain aftermarket VCU/controllers. These controllers (and Tesla toolbox) detect if it's an FSDU or RSDU board, so there must be some identifying information within the CAN traffic. So I'm currently trying to figure out how to identify the boards via CAN. If anyone knows what message to look for, please kindly share!

Ahhh, got it. I was thinking solely from the OI perspective of being basically the same.

I do know that the control board in an LDU Sport vs Base appear physically the exact same, so I would not be surprised if the SDU also uses the same board across variants.