i got the codes 12 and 21.
code 12 is direct battery input to pcm was disconnected with the last 50 key-on cycles.
code 21 isO2s sensor problem (oxygen sensor), upstream or downstream.

how do i go about these? i want to fix them. thanks!

 

the o2 sensors (2ea) are on both sides of your cat convert. one before and one after. this give the comput how well the convert is working, as well as a better ref to adj the fuel curve. as with any parts that get real hot, spray the Heck out of it with liquid wrench or wd-40 (or sim product) and let it sit overnight. i've heard that the upstream sensor goes first ('cause of the heat), but no first hand. try pulling the sensors and see if they are plugged with soot/carbon. worked with an older car i had. i used a BBQ grill brush to clean that one, put it was real plugged up. the book i got says that while cold the sensor heater elements should be 5-7 ohms or replace. as far as what brands work Good with the neon, no clue. i've used bosch, but that's just me. good luck.

 

No, upstream is on the exhaust manifold and the downstream is just before the cat.

 

my bad, my 96 has less than 85K's so i didn't look. just spilling Gen Exp.

 

me and my friend are going swap the one on the pipe with the one on the manifold in two weeks.

i know this is a dodge forum BUT my girlfriend's sister has her SES light on for awhile now on her 2002 Nissan Pathfinder and i was wondering if you could help me find the trouble codes or what ever you call them (In car ECM Diagnostics/ECM Reset procedure). if you can reply back ASAP TODAY it be nice. thanks again!