Issues w/ multiple devices on CAN bus?

[Matt93SE]

Please help a CAN bus n00b! (My last race car had a carburetor!)

So my FRS has an 86Nanny installed and I'm running EcuTek tune. I had no problem connecting the EcuTek bluetooth dongle and logging engine data to my phone.

I recently installed an AIM dash and it also connects to the CAN bus (via tapping into the wires, not onto the OBD connector like the others)... But now I am unable to connect the EcuTek dongle as well.

I tried to get it to connect so I could log some engine data during a track day, but after a couple minutes the phone just timed out. I stuffed my phone inside my race suit and took off, and only once I was on track did I realize my AIM dash wasn't communicating either.. I pitted and cycled power and the AIM dash started working again, but I didn't bother trying to log any more engine data.

The AIM has a setting where it can be invisible (listen only) on the CAN bus, or to include a 120ohm termination resistor and signal the end of line. I have it set to be invisible, so I didn't think it would cause any issues.

Anyone know if there's a limitation to the stuff that can be connected to CAN bus?
considering I'm not running the stereo, airbag, TPMS, etc etc etc (because race car), I would think there shouldn't be an issue with too many listeners on the bus..

Hoping y'all have some ideas to help out a n00b.
Thanks!

[automator]

It's possible that the addition of the AIM is pulling the CAN signals down so far that they're effectively shunted. Or, the mere placement of the device on the cabling is causing issues with signal propagation along the line (noise, jitter,level).
Do you have a link to the device's manufacturer?

-p

[steve99]

Each device on buss needs to have separate address


As you have two logging devices they likely have same address and hence clash


Unless the aim dash can have a selectable can address your not going to be able to log with exited at same time

[Matt93SE]

I'll admit I don't know what I'm talking about, but the AIM is only a listener on the CAN.. I have it set to be "invisible". does it still need/have an address?

Since I have the radio, TPMS, and several other things removed from the bus, I would think there's fewer nodes on it and shouldn't pull it down. BUT depending on how it's connected, all of my crap could be causing issues. (how many busses are actually in this car? how many nodes can be supported on a single bus? Is the current setup exceeding that limit?) lotsa questions, not sure if there's a right answer that doesn't start with "well it depends".. haha.

the AIM is connected to the wiring just behind the factory OBDII plug via t-taps (same location as previous owner), 86Nanny plugged into the OBDII port, and the ECUTEK dongle is plugged into the end of the 86Nanny cable.

pardon MS-paint level artistry...

Haven't had an issues with the 86Nanny in all of this, but that doesn't mean that the combination isn't overloading the circuit... with the ECUTEK at the end, maybe there's just enough noise and loss that it's not communicating while the others do.

[steve99]

If its only listening it might not get all its needed parameters.


Usually all logging type devices get assined same can address so they clash


Also the ecu priorities runnong the engine over providing log data requests. if you ask for too much data it gets chopped off if ecu gets busy doing what it needs to do.


Try limiting the number of parameters ecutek is asking for and maybe on the dash as well, might help

[Matt93SE]

... So after sitting a couple weeks, I go outside to fiddle with the car tonight and all of it works just fine. Dammit Murphy! I don't need to log data sitting in my driveway!