I swear I read somewhere that any ground would work…
ok, that’s what I thought @PJTX… I didn’t think it needed to be on the arduino… just something to complete the circuit. I was thinking the same thing about it still giving the “probe fail” with nothing in there. Bad arduino maybe?
Good luck
Yeah, it’s acting like your A5 pin is shorted to ground. As a last attempt, you might make sure that there are no screws or anything else touching your Arduino/grbl shield, maybe going so far as to take it out of the enclosure.
@PJTX I’m going to try chilipeppr, but I can’t get it to detect my arduino. Any tips? I have connected to the server ok, but it won’t “find” any serial ports (usb). USG and Easel work no problem and neither are running…
Make sure you pick “grbl” in the buffer settings in the bottom right section in Chilipeppr, I think it defaults to “default”
lmao I didn’t notice the “expand window” button. DOOH!
Still get the probe fail in chilipeppr… I think I’m going to call it a bad board/pin/something beyond what I can do
well, I spoke to @JohnHayes at Inventables (super helpful guy. Spent a lot of time helping me resolve a bent lead screw issue… twice). They are going to pass this on to their engineering team and see what they come up with. I’ll be sure to post the fix if/when we find one. Still thinking a bad arduino since it still doesn’t work with the touch plate wiring completely taken out, but we’ll see.
Ok, Possiblya silly question because i dont want to tear my system apart to find out,
Does tthe socket for A5 pass through the board? could you possibly be grounding the A5 pin out on the enclosure beneath the arduino?
I have my touch plate grounded out to the terminal next to the “Z” pot and aside from having issues from a bad phono socket thatI used for convenient disconnect of the touch plate, i have had no other issues. However prior to changing that socket, i would intermittently have similar problems but would at least get a twitch from the machine before it alarmed and locked out.
Good thought. I don’t know if it does or not, but since the error still occurs when the header and wire are remove from the socket, I am thinking that if it is grounding out from the pin it is because the board is messed up. It’s an interesting thing to explore. I’m cutting now and don’t want to tear the machine apart any more today, but when I hear from Inventables and/or replace the arduino I’ll check that out.
i run my ground to the gshield ground just like you have it in the picture. no problem there
i had the exact same issue. no love on A5. i even tested with a voltmeter no current that i could see. i haven’t taken mine out yet to test but perhaps its not even soldered? i dont know but i’m moving away from arudino in the comming weeks so its not a huge deal just wanted to let the OP he isn’t alone 
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I’ve not seen this pinout of the UNO board for the X-Carve. very cool! i’m copying that puppy & putting it into my X-Carve folder!!! thanks!
Russ from Coral Springs, Fl.
It’s available on Grbl main wiki. In the connecting grbl page. Just beware that the picture shown here is the pin diagram for Grbl v0.8, not Grbl v0.9. The only difference is the spindle enable and Z-limit pins have switched places, and the spindle enable is more of a spindle speed.
Well, I hate to admit this but I got it figured out… It turns out when I hooked up my multimeter I read 4.9v but the actual reading was .49v. I guess I was being hopeful and moved the decimal point in my head. 
Inventables’ amazing customer service is sending me out a new Arduino. Thanks to everyone who tried to help me, particularly @PJTX and @AlanDavis. Again, people like you are what make this community so awesome!
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Understood. & thanks.
Russ
awesome you figured out. your symptoms sounded like low voltage but i was at a loss since you said i measured fine! just noticed your post was from last week, did you get it all sorted out with a new board yet?
Yep 
works perfectly! Had a couple other issues creep in (y-axis kept getting misaligned and z axis making some weird noises) tightened some belts and wheels, lubed the delrin nut and good to go!
Well I was setting up my Z-Probe today and ran into some similar issues as you, Jonathan. I went through the same process of hooking everything up, when going to test I get the probe fail message immediately. I disconnected from A5 pin and ran the test again and still got probe fail. I guess I’ve got a bad Arduino as well 
How are you wiring up the probe? Are you sure it is on the correct pin? A5 is the 6th pin in that header, it starts at 0. Which ground are you using?
I have a stack of arduinos I have been using for years and I have never had a bad one.