Making a USB-to-ECU piggyback module lead (non-LR)

[skidrov]

Wanting to pick the brains of the electronically astute...

I have a KTM RC390 motorcycle that I have fitted an ECU piggy-back module to. All working well BUT to buy the "factory" USB-to-module lead for diagnostics is an eye-watering $95.... Wanting to make my own lead.

It terminates on the module to a Sumitomo 4-pin MT090 plug:

189274

And of course, the other end is a USB-A, which has to follow standard conventions:

189275

Have bought the unterminated versions of each.

My question is: can I use a multimeter connected to the MT090 (unterminated, while connected to the module) to determine which leads are the +5V & ground, compared to the +Data / -Data? I can't figure out how to differentiate between the ground and the -D wire. I obviously don't want to connect the +5V to the +D or -D and fry the module...

Thanks in advance!

[loanrangie]

I have a triumph Daytona T595 and program the original ECU using an app called Tumeecu and VAG type USB obd cable. This app also works with ktms I believe.
No need for an additional ECU or cable.

[skidrov]

Thanks, but I need to make the lead - need to use some specific PC software which relies on a USB connection...

[loanrangie]

Thanks, but I need to make the lead - need to use some specific PC software which relies on a USB connection...

But will the lead work as there are probably differing protocols involved.

[skidrov]

Yes, as it needs to come back to a standard USB PC protocol/pin-out.

It's "simply" [emoji12] a matter of correctly identifying the 5V power side v the 3V data side. With the thing I am unsure of being the differentiation between ground and -D.

[BradC]

If I was trying to pick Gnd from D- I'd probe around with my meter in both Ohms and Diode Check mode. Put the negative on the chassis and poke around with the positive probe. On any meter I've used recently they are both well current limited. D- will either be floating or have clamps on it (should have a hard clamp at about 0.6V over 3.3V). Gnd will just be a hard Gnd.