These controllers are weak and often pop for no apparent reason. Check for shorts to frame on the battery plug. This may indicate a shorted mosfet in the controller. Heres a little secret: swap the controllers, reprogram of course for master and slave, make sure battery is fully charged and clean clean clean -a voltage leak to frame can upset these tempermental controllers. Good luck

code -68
Description: PMT enable signal from slave control to master at PL21 (wire #49) drops below 5v.
Symptom:
Control will not operate. Master is indicating that the slave control has shut down but does not indicate why.

Possible Cause:
- Slave control has shut down.
- Install handset in slave control and monitor reading as the truck is operated. Make sure the **** of the handset is turned fully clockwise.
- Verify the connection between the master control PL21 and the Slave control RP10 (wire #49).

you either have a bad connection on that wire or one of the controllers is bad.
But verify all fuses and connections are good before replacing any controller and remember if you do replace a controller it has to be programmed to recommended factory settings after installing it.