Welcome to NICO Club!
Which year engine and ECU are you using? Which light (CEL or on the ECU and what color(s) please)? Blinking or just on? That will be helpful info, thanks.
If OBD-1, the computer could be stuck in the wrong mode and you'll need to use the key and turn the screw to set it back. Then again, it could be that they should be on, or off. I'm not sure. I would look at the FSM for that particular engine/ ECU combination. You might find yours here if you look around: