while trying to reset bed leveling, I accidentally drove the e3d tip head into the clip that hold the glass… saw a little smoke came out of the extruder so I powered off… now in pronterface I get this message. anyone knows what this means and how to reset it?
I tried sending M999 as suggested below but error still persist…
Also hitting the “reset” button on the board doesn’t help either…
Looks like you’re not getting a signal from the thermistor. Could be damaged, could have just some loose. If you shorted it to 12V, you could have even fried the ADC pin, but that doesn’t sound likely.
Yes I’m afraid I may have fried something… I saw smoke (puff)
You broke the temperature measurement circuit, no software will help you as it’s physically broken.
Oh sad day 
will trace down which component exactly broken. I knew that clip is trouble from first time I saw it.
How else does anyone secure the glass?
You can switch to second extruder slot and use it, just change firmware settings, change termistor and reconnect heater, step driver and termistor to second extruder slot on RAMPS.
FIrst disconnect your thermistor wires from the controller board and test the resistance across them. If you read about 100K ohms, those components are fine (which means you probably have damage on the controller board you’ll have to route around. If you read an open circuit, then the problem is the thermistor itself, or the wires connecting it.
Yeah definitely the thermistor. Just find one on ebay and replace it. Also check that your tip didn’t get messed up.
Disconnect and pulled out the thermistor and turned out one of the thermistor’s leg completely loose and appear to be burnt.
Replaced with new one and error went away on its own. Thx all