Car died, now won't start. AP won't connect

Voltage won't necesarrily tell you if the battery is bad. I'd still swap batteries with a good one to rule that out for sure, before tearing into wire harnesses.

 

Make sure your intake clamp hasn't rubbed through wires on the ECU harness. Check the large relay fuses in the engine bay. Check the starter signal wire harness, located just under the throttle body. That clip has issues on the gen 1 starting but wouldn't cause the other issues.

 

I believe 12.2 is complete dead battery. Back when I was a tech 12.6 is full 12.4 is 50-75% charge and under that is pretty much dead

Edit: all I could find in this short time but this is basically what I was taught as a tech at Nissan

https://www.batterystuff.com/blog/how-to-tell-if-your-battery-is-bad.html

 

Interesting, used the other battery to fire up a high compression mazda3 engine then swapped it over. Either way, it did not end up being the battery.

After rechecking all the fuses and wiring, I found a switch in the glovebox that I didn't recognize. I talked to the original owner of the car and that switch was supposed to be wired up as a bypass for the oil pressure gauge. That way in case the gauge was incorrectly reading zero and cutting off the ecu, the switch could override. Well, it was wired wrong and was also a cut switch for the ecu. That managed to get knocked and switched off. I was able to flip it back and the ecu came back and car functions normally.

Thank you everyone for all your suggestions, you all had great info that kept me thinking and tracking down the issue. I appreciate the help you offered, even though it ended up being an issue that would have not normally occurred in most cars. It sounds like a few people have run into symptoms like this in the past and hopefully this thread can help them troubleshoot as it did me. Thanks guys, I love the community here.

 

Glad you got it sorted out

 

Never would have guessed a mis-wired switch from previous owner. Congrats on the unintentional kill switch.

 

Sorry to spark an old thread but i just had the exact same problem on the way home from grocery store. Car just died on me like as if it lost power or gas or just as if someone turned key to the off position while driving. I immediately started looking at my oil pressure gauges as it was flashing and beeping at me but it gladly was a false alarm. i pushed car to the curb and thank the lord i was in my neighborhood already. So after jumping the battery and nothing i then decide to change the key fob battery as i thought maybe it had something to do with it due to the immobilizer light on dash flashing like you reported above. and weeks leading up to this i have been having strange issues with horn not working when locking my car periodically. So i did a google search and hit the forums and saw this thread and started hitting the fuses looking for a broken bridge. and bam!!!! there it was the only 15amp yellow guy in the kickbox panel. (gen pu) 15A ENG fuse. popped in a freshly and back to life she breathes. Nothing but smiles for me!! hope this will help relive some trouble shooting and wrench throwing for some future people with the same odd very random and annoying yet gut wrenching phenomenon.