Does anyone know where the ecu is located on an 87. I’ve only seen people talk about 3rd gen and up.

 

The ecu is located under the passenger side seat under the carpet I believe I’ll check my FSM see what it said if I recalled what I seen

 

My 86.5 Hardbody was under the passenger seat...Have you bothered to even look? It's usual only two places on older Nissan(s) under the front passenger seat or under the dash center control center with the emitting diodes facing the front passenger so you can read the codes....