Cant quite remember the codes(there are leds to check for safety circuits, doors etc), but the can bus resistance is critical to normal operation. They seem to be very flighty, so check your resistors at the end of the serial buses and its ohmage. I think about 70 ohms is about right(from memory). Also as a safety flag, you can short out ALL of the locks via the main pcb with 1 wire(there seem to be no monitor between doors). Its handy when needing to bump the lift but dangerous if forgotten.