So my wife totaled my 06 Pac so I got an 08 LX all wheel drive with 75K miles. It's got the 4.0L engine and 6 speed trans. I drove it from Virginia to NY with no problem. This week out of the blue the trans will not engage into any forward gear after driving it all morning..Pulled into a driveway to turn around. I put it into reverse to back up, then no forward drive in any position. It will go into reverse but won't go forward. It threw 2 MIL codes. PO792 (Intermediate shaft speed Sensor A) and PO731 (Gear 1 incorrect ratio). I disconnected the battery and cleaned contacts. Pulled the regulator wires from the alternator and started the car. After shifting through drive gears it now engages into drive. It was ok for a week or so and then it happened again today. This time I just shut it off for a few minutes and it went back into gear. Does anyone have an idea of whats causing this? The transmission shifts kind of hard from 2'nd to 3'rd, but otherwise shifts nicely in all other gears. No noise from the trans and fluid is clean and at correct level..Could this possibly be caused by a bad diode in the alternator or a bad ground somewhere???? Hoping it's not mechanical......... Someone please help!!!!!

 

I can't speak to your specific problem, but plenty of others have experienced how the alternator in the pacifica can cause trans issues. My 06 Pacifica Touring stared whining, shifting hard into and out of reverse and drive, and got stuck in low gears refusing to shift recently. I had recently replaced the serpentine belt, which can sometimes cause other old parts run by the same belt to start failing. My alternator tested ok (14v) at the auto parts store, but I was getting several transmission related codes (P0731, P0732, P1790, P0700, P0720). On the advice of 2 other forum threads, I decided to change the alternator anyway. It solved all my shifting problems and the engine codes have not returned since. As a transmission is so expensive, it might be worth your while to take a look at these threads and see if this might work for you. Good luck!

https://www.chryslerforum.com/forum/chrysler-pacifica-15/surging-idle-speedometer-showing-speed-when-stopped-13761/

https://www.chryslerforum.com/forum/chrysler-pacifica-15/pacifica-p0700-p0720-tricky-issue-resolved-15556/

 

Thanks for the reply. I am quite aware of the alternator causing trans problems. I had an 06 touring that was throwing trans codes and causing the speedo to show 15mph when the vehicle was not moving. Changing the alternator fixed the issue. This 08 has the 6 speed trans which has no trans dip stick. I suspected the fluid might be off but had no way to check it. I took it to a dealer who told me where the fluid level for this vehicle should be on the stick that has the end marked off in centimeters (50cm or roughly 2 inches up the stick when the stick hits the bottom stop in the trans pan). Turns out that it was almost 2 full quarts over filled. I removed the fluid and had the shift learning software reset to factory default. After a week or so the trans is shifting much better from 2'nd to 3'rd whereas it was really banging into gear before. It's still not a smooth as the rest of the shifts but it is much better and I have not experienced the trans refusing to shift into any forward gear like it did a couple times before I adjusted the fluid level. Hopefully the fluid level was the culprit, but if it does happen again I likely will replace the alternator. Seems these vehicles are way too sensitive when it comes to the alternator output. Thanks again...Dave

 

OK so a year later, I still have not had any of the going into gear issues since I corrected the fluid level.. These 6 speed trannys do not come with a trans fluid level stick, and I didn't know at the time where the fluid should be on a stick. Once I found out how to check it and where the fluid level should be, I found the issue....For those who don't know how to check it, you can use your oil dip stick, just wipe it clean before checking the trans..With my 6 speed trans, check it when HOT in PARK with the engine idling, you insert the stick slowly until it hits a stop. Remove the stick and read the level. With this 6 speed tranny, the FULL line is exactly 2 inches up from the bottom of the stick. I did buy a trans fluid stick to check it and the part that goes into the trans is in increments of 1 to 10 centimeters. The proper lever for this trans was 50 centimeters which translates to pretty much exactly 2 inches, and using the engine oil dip stick is a whole lot easier and convienient. Just be careful not to force it into the trans fluid tube. Insert it gently and it will hit a built in stop which you will see if you ever change the fluid yourself. Two inches is the MAXIMUM level for my transmission. I think you have about 1/4" below the 2 inch mark for it to be in the OK zone...