It's as accurate as the sensors the PCM reads. You can leave it plugged in all the time if you want. It powers up and down on it's own. You can unplug it if you want. Won't hurt anything but is not needed unless you have to access the OBD port for some other reason (i.e. scanner).
They're pretty accurate. It's the same info your PCM is reading from your sensors. One benefit is that it gives you a better idea what your trans temp and engine temp is as a quantitative value instead of the dummy gauge on the dash.
Here is a pic of mine with trans temp (TFT), engine temp (FwT), volts, and RPM. You can display 4 gauges at a time. It plugs into your OBDII port constantly. It can also read CEL codes. Just disconnect it when going for your smog check.
I love mine. I leave it plugged in all the time. it shuts itself after 12 seconds of no input from the computer. I have mine set up almost identical to jh818, except that my water temp is on top and trans temp is on the bottom. I really like it.
The only thing it displays from your lie-o-meter, I believe, is your mpg. There is no outside temp, nor miles to empty, nor compass.
Since I tow, I use it to track trans temp.
not to worried about the outside temp, compass or miles till empty but miles till empty would be nice but its not ever even close to acurate. it always used to say anywhere from 240-250 and i get 200-220
Originally Posted by jh818
There have been threads in the Excursion forum on fixing that display. Gently pull it down and see if you find some loose or broken off chips and resolder them back on.
Yeah my chips are actually fried and burnt off. 2 are not even attached anymore. and its gonna cost $100 to fix.