I'd like to start a thread about the diagnostics on the later 7s, such as the Sigma and Duratec cars using the locked MBE ECUs. I am attempting to understand what is and isn't possible from the diagnostic connector. I'm not interested in mapping the car, just reviewing the data from the car. Now I understand Easymap and the MBE 985 cable is the standard method of gaining such insights, and I've placed my order for a cable this weekend.
I would however like to understand why this is specifically needed and why there seems to be a general acceptance the only solution which works. During my build I did plug in a generic OBDII CAN supporting diagnostic tool, and as far as I could tell it gave me a sensible coolant temp reading, which was very close to that on the dash gauge. So I am a little cynical about the limits.
I'd also like to compose a post for my blog, I'm sure there are others that have similar queries.
Additionally, I'd prefer to use a non-Windows tool to log and chart the diagnostics data. Maybe even write a bespoke tool I can hang off my Linux box I have in my garage, or use on a raspberry pi etc. Lastly depending on the information I can put together at an early stage I'm going to try and mirror the USB stream from the MBE985 cable being feed into Easymap and use Wireshark on Linux using the Linux SocketCan driver. Hopefully this should give me the ability to inspect the data stream and identified the values/identifiers I'm interested in.
I know this is a relatively specialized area, but the expertise here seems boundless at times, so I'm sure there's sufficient knowledge to support this endeavour. Thanks for your support, fingers crossed.
What I believe to be the case...... but please correct me!
The 7 has or uses;
- An SAE J1962 diagnostic connector (pretty standard)
- A single ECU, which uses CAN bus, it is unclear whether it is 11 bit or 29 bit wide implementation. Bit rate is also unknown.
- Standard ISO 15765-4 d Pins 6 (CAN_L) & Pin 14 (CAN_H) are utilized for signaling.
- Identifiers and Payloads within the data stream are not published, sticking point and issue or concern. Hope they are encoded in a simple manner.
To me, the final point is where the issue occurs, but I might be wrong. The ECU developers have either not published or not used common identifiers and payloads permitting the use of generic tools.
I see no reason why with some time and effort aspects of this can't be overcome. If I can get access to the stream with Wireshark, using the CAN protocol analyser it is entirely possible different identifiers could be inspected and charted with a Wireshark IO Graph etc and thus deciphered. For example, the identifier for engine speed would be clear when the throttle is pressed.
Or am I missing something here?
I appreciate this thread is going to turn many people away. For me, it's an interesting topic and while CAN is totally new to me, the concept of protocols deciphering isn't. Plus I'd really like more freedom when monitoring the car. Easymap serves a purpose but I really don't want a Windows host just for that. If you can offer some knowledge or experience from the point of the 7 its implementation of CAN and connectivity then I'd appreciate it.