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So I'm curious, does anyone know if the j2534 protocol means that my gm nano is capable of being used as pass thru for any make for module programming? Or is it still tied to gm and its vpw and CAN protocols? I've been looking and haven't found definitive explanation of function. Example, why can't Ford fjds use my gm nano as pass thru for module programming? Or is it a protocol switch during use for programming?

Cincinnatus wrote:So I'm curious, does anyone know if the j2534 protocol means that my gm nano is capable of being used as pass thru for any make for module programming? Or is it still tied to gm and its vpw and CAN protocols? I've been looking and haven't found definitive explanation of function. Example, why can't Ford fjds use my gm nano as pass thru for module programming? Or is it a protocol switch during use for programming?

Depends if your vx nano supports the require protocol to use with Fords.

This is why allscanner (the manufactures) have different versions of their tool to support different protocols.

I know different makes use different comm protocols, but the j2534 is universal among manufacturers, so that's where I'm confused. It must switch from say GM's j1850 vpw to j2534 when the programming event occurs, but only then is the j2534 in use, otherwise it's vpw.

Cincinnatus wrote:I know different makes use different comm protocols, but the j2534 is universal among manufacturers, so that's where I'm confused. It must switch from say GM's j1850 vpw to j2534 when the programming event occurs, but only then is the j2534 in use, otherwise it's vpw.

Oh I see the confusion!

I can answer this.. since well.. I have just made a J2534 DLL for my own OBDX tools.


Ok so we have the following setup:

Dealership software <-> J2534 DLL <-> Scantool <-> Car

The dealership communicates with the standardized J2534 protocol, this is bascially a set of commands that MUST be present in a J2534 DLL made by the scantool manufacture such as allscanner (VX Nano), Bosch, Drewtech ect.
The manufactures J2534 DLL then speaks to its connected scantool (made by that manufacture) to then communicate to the car.

The dealership software then makes commands to the J2534 DLL to change the OBD2 protocol to VPW, or CANbus. The J2534 DLL then communicates to the scantool and commands the scantool to use that protocol, or send a message ect.

So even thought the VX Nano suppports the J2534 compliancy, this does not mean the vx nano will supported the vehicles OBD2 protocol. Hopefully that makes sense!

That's what I thought, though I can use my gm nano with forscan on several Ford's so far, though it was only diagnostics and live data (which still wasn't GM's vpw) though it wouldn't work on one vehicle (and I forget which one it was, I think it was an old explorer, and I had to use my elm). I may just try to see if fjds will work and report back.

Doesn't really make sense to call j2534 a pass thru when it's really an intermediary between software and interface, not pass thru between software and module being programmed.

Cincinnatus wrote:Doesn't really make sense to call j2534 a pass thru when it's really an intermediary between software and interface, not pass thru between software and module being programmed.

I gues sit depends how you look at it.

Personally I see "Direct Connection" as Software to scantool.
And a "Passthrough" as the software "Passes" the information through the J2534 API to the scantool.

Well.. thats my interpretation at least!

I believe my mistake was thinking the j2534 was between tool and ECU (or between software and ECU, passing thru the tool), but it is between software and tool only.

Cincinnatus wrote:but it is between software and tool only.

That's right!

As the typical whole story flows ...
End user software <--> J2534 DLL <--> VCI DLL <--> VCI <--> VCI Protocol (VPW/CAN/...) <--> Unit that speaks VCI configured protocol (i.e. PCM/TCM/...).

The VCI DLL may have a J2534 API.

-Enjoy