Diving into the intricacies of vehicle diagnostics has been a fascinating journey, sparked initially by the Uconnect hack and leading me deep into the world of OBD2 and CANBUS. My exploration using the OBDLink MX has unveiled the power of AT & ST commands, and to further enhance data capture, I’m moving to a wired USB OBD2 ELM327 module. This switch is essential because Bluetooth modules, despite tuning efforts, struggle with continuous data streams, often resulting in buffer overruns. A wired connection promises uninterrupted data flow, crucial for comprehensive analysis.
My recent “aha!” moment involved the extended PIDs revealed during full PID scans with Torque. The responses containing “7F” highlighted NULL PIDs, but more importantly, they pointed to the existence of skipped PIDs that are likely functional and data-rich. By analyzing a cleaned version of my full PID scan data in Excel, I’m working to pinpoint these untapped PIDs. Essentially, all the PIDs not initially provided (Hex 0-F) are potential candidates for enhanced parameters, possibly including data relevant to a 2011 GMC, such as oil temperature.
This deeper dive into PIDs is aimed at narrowing down functional parameters, comparing them against known PIDs, and starting the process of reverse engineering. Once the USB ELM scanner is online, I intend to monitor CANBUS communication to ascertain if data points like TPMS pressure and temperature are transmitted from the BCM to the ECM – and if similar pathways exist for other parameters, such as oil temperature in a 2011 GMC. Switching the Driver Information Center (DIC) to the TPMS screen during a scan session might even consolidate data acquisition.
This investigation runs parallel to my curiosity about an OBD2 window rollup/rolldown module. Understanding the lock/unlock sequence that triggers the module to control all four windows has been another interesting side project. To simultaneously analyze this module and sniff CANBUS traffic, I plan to use an OBD2 splitter cable. This setup will allow me to observe the interactions while the window module is active on the CANBUS. As detailed in my forum thread and accompanying YouTube video (linked below), this module also activates hazard lights upon door opening and closing – a potentially useful safety feature.
http://www.ssforums.com/forum/electronics/13170-window-roll-down-function.html
For those interested in delving further into vehicle bus hacking, these resources provide excellent primers:
a complete guide to hacking your vehicle bus on the cheap & easy – part 1 (hardware interface) |
a complete guide to hacking your vehicle bus on the cheap & easy – part 2 (interpreting the data) |
https://cdn.sparkfun.com/assets/learn_tutorials/8/3/ELM327DS.pdf
http://opengarages.org/handbook/2014_car_hackers_handbook_compressed.pdf
Regarding device mounting, I appreciate the creative tablet and phone setups I’ve seen. I’m leaning towards a rearview mirror mount for my Android phone to serve as dedicated gauges, and a separate dash mount for my iPhone. With a V1 radar detector and BlendMount in my plans, positioning the Android Torque display to the left of the mirror in landscape mode seems ideal. This might necessitate a custom bracket using RAM Mounts components.
I will share further updates as my exploration progresses. Stay tuned for more insights into accessing and interpreting your vehicle’s data, potentially including parameters like the 2011 Gmc Obd2 Oil Temperature!
