GM Reverse Engineering

[The1]

did we get anywhere on teh brake bleeding? need to bleed my VX brakes, i changed the fluid in res and bled the brakes but you can see crap coming back in the res cause the abs didn't cycle.

[Tazzi]

did we get anywhere on teh brake bleeding? need to bleed my VX brakes, i changed the fluid in res and bled the brakes but you can see crap coming back in the res cause the abs didn't cycle.

Well on the VY/VZ's.. Didnt get much further then what was posted up before. Im unsure if the tech2 is waiting for the abs module to respond with a specific frame to those mode6 frames or if the mode1 table requests are meant to change in a specific manner (which I guess they should).

Since doing all this on bench using my "fake" abs module.. my tech2 just shits it self as it doesnt get the intended response.. the fault on screen says something like invalid response.
Actually does that on any of the "function tests", pumps out the large frames then has a sad

Id assume that for VT/VX commys, the ABS bleed command would be slightly different like everything else. If I have the tables 0-5 ALDL response of the ABS module for the VX abs module, I should be able to try and log the bleed procedure using my fake module.... this is assuming that its not going to pump out those large mode6 frames again!

Have absolutely no clue what those massive frames are doing. Wouldn't think that they are the actual bleed since mode6 isnt the manual override?

[Tazzi]

Did one last attempt on the abs bleed.. yeah no go. Does the same on all years for vy/vz's. Will be a matter of getting 1 or 2 actual logs of bleeds to find the mode4 frame.

Now looking into logging the OBD2 protocol that the tech2 uses for the V8's/VZ's
Good to see that the ELM cables are cheap as, although I keep reading about "different protocols". I thought the whole point of OBD2 was to standardize this stuff!

Also doesnt seem to be any software that logs and displays the OBD2 raw data. Guessing it will be a matter of using a serialport monitor/terminal to watch whats coming in and out from the port in use (excuse if Im off track.. havent even seen what the obd2 logs/data looks like.. let alone any official sae documents.).

[The1]

VT/VX would be different abs? I havn't had a play yet might see what tables there are on the vx one day.

[antus]

Elm is a bit of a crap protocol. You would be better off with an AVT. Pm me if you might be interested. OBD2 Standardised bits and pieces including the SAE PIDs but several hardware protocol options. It also standardised what protocols are on what pins but left a couple open to manufacturer disgression. To be obd 2 it needs to be one of the official protocols and support the SAE pids and DTCs. Then each manufacturer has propriety PIDs and DTCs beyond the basics.

[Tazzi]

Elm is a bit of a crap protocol. You would be better off with an AVT. Pm me if you might be interested. OBD2 Standardised bits and pieces including the SAE PIDs but several hardware protocol options. It also standardised what protocols are on what pins but left a couple open to manufacturer disgression. To be obd 2 it needs to be one of the official protocols and support the SAE pids and DTCs. Then each manufacturer has propriety PIDs and DTCs beyond the basics.

Ok, thats making more sense then. I figured there must of been a "basis" that they all must follow, then the manufactures add additional stuff beyond the standard.

As for the AVT.. might be the way to go. Quick google shows that it has a RS232 ending.. would prefer the usb since usb->serial converters just never work for me. Already bought an ELM which rocked up DOA.. another one on the way (well.. should been here already).
Guess Ill need to suss out the original SAE documents. Get a feel for what Im going into.
At least if obd2 is "standardized"... cant be a bigger mess than ALDL, although obviously thats comparing oranges and apples between protocols.

An ELM would work anyways wouldnt it? It is the cheaper option but I dont actually have any pcms/engine related modules to log, only got the tech2 which Ill be looking into throwing together some software quickly to falsify module responses to the tech2 like iv done previously. (assuming it works in the same manner). Anyone actually logged what passes through the serialport of using any program? eg efilive or one of the 100's of OBD2 generic dtc readers?

[antus]

yeah it'll work, it doesnt just pass raw data on to the bus. when transmitting you need to set up the headers/addressing then send the data, and send it all in an ascii representation of hex. You cant just put it in vpw mode and send a raw packet, which makes it rather clumsy. Also no vpw 4x or block transfers, so if those are used by the tech 2 you wont be able to see them. And if you get an avt you can start playing these games too http://pcmhacking.net/forums/viewtopic.php?f=3&t=3111

[Tazzi]

Well youv sold me, AVT it is.

Headers/addressing.. guessing thats just sorting out where its going ect. Will need do hands on work to understand it all, right now its a bit confusing without an example.
Ooooooo nice work Ant, didnt know you had software up and running! Very cool!

[Tazzi]

Oh daaaaammnnn!! Im either seeing things or every AVT cable is $300+! Any other cheaper choices?! Not really affordable for the average joe.

[antus]

not currently, if your budget cant extend that far you might have to make do with elm/stn.