Successfully using multiple OBD-II instruments

[Focus-Ak]

It has been generally reported that multiple OBD-II instruments, and the UltraGauge in particular, often don't work when connected to the OBD-II port with a Y-splitter cable.

I just experimented, and found that when using the UltraGauge in this way with another datalogger, that order in which they are connected after the key is turned on (engine not yet running) is what matters. When I connected the UltraGauge last, both devices worked perfectly.

When instead I have both connected initially or if I connected the datalogger last, the datalogger would not connect with the ECU.

It is also important to have cables that pass through all 16 OBD-II connectors. Many do not pass them all through, and although this may not lead to problem with the instrumentation, having a cable that does it all will eliminate that potential pitfall. In my case, I found a ribbon pass-through cable (with all 16 wires) for getting my arrangement up under the dash, then going into a splitter cable. (I don't want a lot of crap hanging onto the front- of-dashboard OEM connector.) But having the two split connectors easily accessible is the difficult part, at least for now - will futz around with that another time.

It is great to be able to use the UltraGauge while I am datalogging, so that I am able to drive as normal, using the instrument cues as usual.