So How Do Scan Tools do it?
In our previous blog post, we described the universal OBD2 process of requesting and receiving CAN data from ECUs. One of the negative points of this system was that it is actually quite slow and information is limited. For those of you with scan tools or access to tuning software like HP Tuners' VCM Scanner program, you may think well they can do it... why can't we? Well.. what we described in the previous blog post was OBD2 Requests using Mode 1 - for retrieving live data. There is a mode, Mode 9, which sets up a MUCH faster response rate.. Oversimplifying here, you would ask an ECU to enter Mode 9 and give it a command of "Send Info" once, and it can send up to 128 different parameters per single request. This is how the majority of paid services do it. Now, again, why can't we? This time, it is because while the FORMAT for Mode 9 is well established and documented by the EPA, the responses are manufacturer specific. And because of this, companies like Snap On, Autel, HP Tuners can pay the OEMs' service fees for this information because it is worth it for them. We simply cannot, and are stuck with reverse engineering the raw CAN or using the slower Mode 1 method of individual request and response.
