Can bus Hacking

SonicVQ · 04-26-2020, 08:51 AM

Quote:

Originally Posted by dts3

So I started my CAN logging software on my laptop and started logging in Uprev, hoping to see the PID requests for each parameter one by one. Logging in Uprev was working and I could see correct parameters. I couldn't see it in my CAN bus logging software.

I was trying to troubleshoot and noticed that I never connected the CAN lines together. So Uprev does all of their PID request logging outside of the CAN bus lines. I was thinking it's coming in over K-line, but I looked in the FSM and I didn't see K-line being brought out to an OBD pin.

We have a K-line BUS but if I remember correctly the FSM says that it's for internal use only, for modules to communicate with each other. Does anyone have any info on this? If I can't see K-line traffic I'm going to have to put a scope on the vendor specific pins, and I REALLY don't want to do that inside of the car.

The latest documentation I have is for a 2016 370z, and I don't think Nissan would have changed anything since. Based on the ROM you posted, your 370 is from 2017 and I would expect it to be the same.

The K-Line is still on pin 7 of the OBD connector and goes directly to pin 117 of the ECU. Nissan sometimes calls it "K-Line" and sometimes calls it "Data Link Connector"

Try this test:
• With the CAN bus not connected, log data and look at the time between samples. The UpRev log shows time in milliseconds.
• Hook up the CAN bus and run the data logging program again.

Since the K-Line runs at 10,400 bits per second, and CAN bus runs at 500,000 bits per second, I would expect the time between data to be much faster with the CAN bus.

I suspect the UpRev software checked the CAN bus for communication, didn't see it and "failed over" to the K-line.
This would allow them to use the same code for older cars (before 2008) that don't have CAN bus.
I look forward to your test results

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