As you can see this is my first post but I have been perusing your forums all day trying to find the answer to my issue.... so... I will post my own question.

My 2001 Pathfinder was running just fine yesterday morning. I get home about 4 hours later I go to start it up and nada. It cranks all day but doesn't turn over. It started once after about 3 tries and died only a few seconds later. Naturally I tried to rev it and it still died (its the old car syndrome I have).

Flash backwards to 2 weeks ago. My check engine light came on and we went to Autozone to have it tested. I am 99.9% sure the code was P0100. Don't hold me to that. Check engine light went off a day later. The car has given me ZERO signs of any issues, driven perfectly fine, no stalling, idling funny,no gauges going nuts, no starting issues...nothing.

Flash back 3 weeks ago when I went to the oil change place and they asked if I wanted fuel injector cleaner put in my tank. Sure. Why the hell not. 2 days later the check engine light comes on. And then goes off. And comes on again.

Flash forward to today. I know very little about fuel injected cars or anything with a computer so I spent most of the day researching everything and anything that would cause my car to not turn over.
I started with the most obvious thing. The battery. I took it to the parts store and they tested it and their lovely little contraption called it a "Bad battery" yay? I replaced the battery and immediately when I hooked it up things didn't seem right. My door bell started dinging and there was a clicking noise. Not good. I thought "Oh god I left the keys in" nope. They were in my pocket. Oooohhhhhkay... Still nothing. Cranky but no starty.

Phew sorry this is long...

I read that sometimes the IPDM (Intelligent Power Distribution Module...or Idiodic Piece of Deceptive Material) will go bad causing a relay to go bad. I have read that you can do a temporary swap on the relays to see if one is indeed bad. The articles I read were for the Titans which apparently the IPDM can be swapped out for theirs because Nissan is evil and doesn't sell them? Nothing makes much sense once I look at my own vehicle. In all reality it will probably go to the shop but I like to have a heads up and try and trouble shoot things on my own because I get screwed a lot at the dealership/repair shops ("Oh the pretty dumb girl doesn't know anything..." ) My husband is military and always gone other wise I would politely ask for him to take care of this...instead, tis me who takes care of things.

Is a temporary relay swap possible to see if it is my IPDM? I took pictures of my junk in the trunk (ok its under the hood but whatever...) There is no ECM relay only one labeled EGI. Also the instructions suggest to switch out the Fog light relay with the ECM relay. Fog light relay is on the driver side fuse box.




I know there are about 532 other possible problems this could be from a MAF circuit malfunction, bad IPDM, bad batteries in keys, bad fuel pump, clogged fuel line, fried wires or anything else.

just trying to solve this before my husband tries to attack the car and starts to think the worst about having to completely rebuild the engine.


Any and all help is very appreciated. If someone helps me with this and its the problem I solemnly swear to send you delightful baked goods in thanks.

The Pathfinder doesn't have an IPDM in that year, some other things to check.... Fuse 62, 63, and 66 @ fuse box underhood, fuse 21, 24, 25, 16, 17, and 8 @ inside fuse box. These are the fuses for anything fuel management-related. Take your key off of your key ring, and even try a 2nd key that will start the truck if you have it.

Look for any other indicators on the cluster when trying to start it. A few electrical reasons this could be happening is the immobilizer system could be faulting, either to a coincidental and poorly timed opened fuse, or RF interference near the key during start (hence try with the key off of the key ring or different key); an opened fuse for anything related to engine or fuel management, bad fuel pump/ECM relay(s)... well the list could go on a bit further but that's reaching out of my area of expertise. If it's the immobilizer acting up, the security light will illuminate to let you know of a problem while the key is on the ON position, this will be the same light that blinks when the key is in the OFF position.

Your ECM relay and both fuel pump relays are under the hood, you should hear/feel them click on when the ignition is on.

It sounds like it's a fuel management issue or no spark by the way you're describing (getting a crank with no start whatsoever), but again I'm no mechanic, I'm an electrical guy. I would think if it was due to a bad injector it would start but run like bleh, if it would even run at all.

Good luck.

There are no fuses labeled with those numbers anywhere. They are all labeled according to what they are. I replaced the fuel filter and checked every single fuse in the entire vehicle to try and rule out the simple stuff. We also noticed that the security light wasn't being normal either. It would come on and stay on or not flash like normal if you had all the doors closed.
The fuel pump "Whirrs" (as it said in the Hayes manual) so at least its trying to do its job. We opened up the trap door to the gas tank and all the wires and connections seemed normal (nothing visually damaged).
I also did the relay swap like I mentioned in the beginning. I swapped the fog lights with both the fuel pump and fuel pump 2 relay switches. Still wouldn't turn over.

Added note: We did take the keys off the rings and even unplugged allllll the extra stuff in the car so see if it was something interfering with stuff. I tried both my key and my husband extra key. I did notice that there was a funky rattle when I shook my key. Maybe I scared my car and now its fearing for its life LOL.

Fortunately our insurance does a free tow to the closest repair place but considering its Saturday I see nothing getting done until Monday. Yippy...skippy.

Hmm, if the security light is acting up it could be the immobilizer or the key cylinder, though I wouldn't necessarily rule other things out. Check to make sure you're getting voltage at the NATS connector on the key cylinder, there should be 12V+ constant on the white/red, and 12V+ when the key is in the Ignition or Start position on the white/black.

Also check the wires at the key cylinder:

White/Blue should be 12V+ in accessory and ignition position
Black/White should be 12V+ in ignition and start
Red/Yellow should be 12V+ in ignition
Black/Yellow AND Red/Black should be 12V+ in the start position

Our old Pathfinder had a bad ignition key cylinder after a few years where it got to the point that it would sometimes start if we jiggled the crap out of it before we replaced it.

There is an awful clicking noise coming from the top of the manifold. The top most "thing" sitting up behind the throttle... *sigh* I don't know what its called. When I moved the throttle just a little there was also the same clicking noise.
I have no idea where the key cylinder is at but we did buy a Haynes manual today. If I have just a testor light can I use that to see if there is any juice at least going to it? Thats what I did with all the relays and fuses.

I am at a loss.

Well... just for giggles the mystery was solved the other day. It was the "immobilizer unit" that apparently kept the car from starting because it thought it was being stolen. Great.
I also had the shifter fixed while I was there. The current solution for it was a giant flower hair pin shoved down into the emergency release switch on the passenger side of the shifter to be able to take it out of park. Safe. I know.

All in all I got ripped off about $1,200. Hooray for me.

I had someone say how I got screwed by the dealer but honestly... I don't care. The area we live in is CONSTANTLY trying to screw over soldiers and the black list of auto repair places here is longer than some of the threads on here. If it breaks again I can blame the dealership. It was something I didn't have to deal with considering all the wiring and computers involved and the labor. I might be $1,200 less in my bank account but at least I know its fixed.