I have an extra "user input" channel on my wideband datalogger. I'd like to read the timing retard signal from the esc to record knock will datalogging. Can I tap into the BLK 485 wire on B7 to pull in this signal? What will the signal look like when the ESC is detecting knock? My datalogger will read a 0-5 volt signal.

 

If it has an ESC module in the engine bay then the B7 signal will be at approx. 9 volts with NO knock. It will be at 0 volts WITH knock.

Can the reader handle voltages greater than 5 volts? If it has an input buffer, some clamps diodes, current limiting, or just a buffered voltage divider then it should be fine. If it has nothing, you might blow the front-end IC out.
If you don't know what it has, the use a simple 2 resistor voltage divider at the input to the reader to make the 8-10 v knock signal a 4 volt signal to allow some margin.

 

I'm checking with the manufacturer to see if voltages > 5v will cause any problems. If I use the voltage divider, do you see any issues that could occur with the ecm due to the added impedence in the circuit?

 

Manufacturer got back with me and said the circuit is protected up to 12v, but recommended using a voltage divider anyway. I'll make up a simple two-resistor divider so the 9v get cut down to about 3.