The Nissan Path

Hey all,

I have an 05 pathfinder automatic with 130,000 miles and a new transmission with an external cooler. I'm having a very hard to figure out issue and I summon the internet for possible help!

It seems to happen most often at higher elevations (+ 7,000 ft.) when going uphill for prolonged periods. The dash lights go out that show which gear I'm in, the 4wd service lights come on, and the car down shifts and won't move out of gear. I can shut the vehicle off for about 15 minutes and it will work again, the check engine light remains on as well as the 4wd service lights. Usually the next time I drive it the 4wd lights are off.

The codes have been all over the place but all are related to communications errors. I have replaced the battery, cables, and rebundled all the wires off of the transmission as I suspected maybe some wires got pinched in the install. NO LUCK!

Latest codes - U1000 - always comes up
P1446 - vent control valve - new on
P1807 - vehicle speed sensor -AT

I have taken it to dealerships, local mechanics, etc. I have no idea whats going on. Is it possibly related to the ECU? I'm out of ideas at this point. Anyone?

Clay

Well, let's start with the P1446 code, which is probably unrelated to the others. If you replaced the vent control valve, already, there's a good chance you may have a lot of dirt inside the vapor canister. I ran into that recently with my 2008. I got a P1448 code, replaced the vent control valve with the update valve and it still set the code. I removed the old one and weighed it and it was 9 oz. heavier than a brand new one. I replaced the canister and no issues since.
The other one is a little trickier. Basically, you should follow the diagnostic procedure for P1807 as stated in the factory service manual for your vehicle. The transmission sends the output shaft speed information to the transfer case via CAN. I could be mistaken, but I believe the output shaft speed sensor is located inside the transmission on this model. Also, there have been issues with pin breakage between the valve body and TCM. So, it's likely either a bad shaft speed sensor, broken pin on the TCM valve body or either a bad TCM or bad 4WD control unit. The problem is figuring out which one, obviously, which is why you need to follow the diagnostics.