3DTouch/Bed leveling randomly stopped working...Tried multiple sensors

[travishauch]

Hi. I've been using the 3D Touch sensor from Geeetech for several months now and have had great success and no issues. The other day I was starting a print and the printer started probing the bed like normal, but on the 3rd probe point it stopped with an error. I restarted the printer and now it's not working at all. The sensor goes up and down twice staying in the up position on the initial test. I tried auto home and the sensor doesn't probe down and the nozzle hits the bed.

The sensor light is not blinking (no error on self test), but the printer is not responding to any M280 commands, either from the menu or sent from the computer.

I have a Geeetech i3 Pro B with a GT2560 A+ board.- Marlin 1.1.4 Firmware

I took my old z-min switch and plugged it in just to make sure the board is respdoning to the z-min pins and it is. I used a multi-meter on the z-min on the 3d touch sensor to see if the circuit is reading closed and I get 138-143 ohms when in the up/down position so I thought the sensor was bad. I bought another and still no luck. I checked the wiring and did a continuity test between the sensor and the board to make sure a wire didn't get busted in my cable chain. Everything is good. I tried the sensor without the extra wiring and still nothing. Next I tried re-flashing the firmware with 1.1.4 again, nothing. I tried 1.1.7 and 1.1.8 from the forums here verifying that BLTouch is enabled. Still not working.

Grasping at straws, i bought another/different sensor. BLTouch sensor (not 3D Touch) and still the same problem. The sensor is probing twice on initial startup and staying in the up position.

The only thing I can think of yet is to replace the board. I don't know what else it could be.

Sorry for the long post, but I'm hoping someone can help me. The printer is only 6 months old. I'd hate to have to replace the board.

[William]

Do not need to insert the Z-min wires,

only need to insert the 3pin connection to the mainboard and you can use the M280 instruction to test,

you should check the extension cable(3pin) is working properly, the other check the solder joints on the mainboard is normal