I have a 95 5spd fed spec , my ecu code is A18-E10-ER0 which references correctly. Im having issues with a snap on triton scan tool. It will only communicate through the consult plug and not the obd2. Anyway that's not that big of a deal but what's really throwing a wrench in things is that its searching for a 4th 02 sensor. I was seeing if anyone else has had this anomaly.

 

normal on early obd2 nissans. you need to use the consult plug or go in with global obd2 when using a real scan tool.

also, while im not 100% sure as its been years since ive been under a 4th gen.....but my 00 only has 1 downstream o2 behind the main cat as its a fed spec. im sure yours is the same.