Code Reader for all GM Modules

[800DiagTech]

I have a shop scan tool that reads DTCs from all my GM modules, but (annoyingly) does not fetch history DTCs. But since I have a OBDLink LX+ - which supports J1850 GM Class II Serial VPW - I wrote an android app to fetch the current and historical DTCs from all my modules.


Which makes me wonder: is there already an app that can read current and historical DTCs from all of the modules on J1850 GM Class II Serial VPW network?

 

[azswiss]

An app is not necessary. You can directly query the network using an ELM327 adapter and a serial terminal app like Kai Morich Serial Terminal.

Below is the command sequence I use to get MIL, Current & Pending DTC's for all modules on my '03 Suburban:
ATZ
ATSPA2
ATH1
ATS1
ATAL
ATSH6CFEF1
1980FF00
1902FF0
1940FF0

The output will be in HEX but is easily converted. The attached Excel spreadsheet translates the HEX into text (note: depending on the vehicle you may need to edit the module addresses).

 

[800DiagTech]

Yeah using AT commands for ELM327 and Kai's terminal app is great, and I have used it a bunch for network sniffing.

My goal is purely convenience. I'm looking strictly for an automated Android app that does the heavy lifting instantly on a phone. If a polished app that reads GM history codes across all modules doesn't already exist, I'll just finish building my own.

 

[azswiss]

Got it, makes sense. Not being a coder I had to be satisfied with setting up a macro in the terminal app to execute that string sequence. Even though the output is HEX as long as I see 00 in both DTC bytes 1 & 2 I know I am OK.

Would definitely be interested in the turnkey app once you get it rolling.

 

[AmpOverload]

Which makes me wonder: is there already an app that can read current and historical DTCs from all of the modules on J1850 GM Class II Serial VPW network?

Short Answer: I don't know of any.

Long Answer:

Two popular Android apps on this forum are 'Torque Pro' and 'Car Scanner'.

I haven't run Torque Pro in a long time, but my recollection is that it didn't handle Service/Mode $19 (which would be required to query NON-emission-related DTCs) at all.

I've never run an official version of 'Car Scanner', but the beta versions are made publicly available and I've run a couple of versions of it that way, about a year apart. Car Scanner ostensibly provides DTC support but there were (and probably still are) bugs in this app, including at least one in the Service/Mode $19 DTC reporting, so I don't consider it trustworthy.

Having said that, be aware that providing such an app might be a "tall" task. GM is infamously poor at adhering to standards. What might work on your vehicle might fail on another GM vehicle. I don't mean to discourage your effort. In fact, I wish you great success. I speak now only to provide a forewarning of the possible frustrations, should you seek for your app to have broad acceptance. If you're just writing it for your own use, then I say "Go for it!" since I've written several useful little Android apps that do "neat" OBD2 things.

 

[BeverlyDay92]

Mode $19 is the gap that kills everything else. If your app handles that properly, you're solving what nobody else has.