Dakota Durango Forum banner

P1698 PCM/TCM buss comm failure

2634 Views 8 Replies 2 Participants Last post by  DoubleJ
I tried over in the transmission forum, no luck on three different threads, hopefully you all can help. Recap below:

Here's the story: Truck has always had an occasional issue where the TCM loses power, the trans drops a gear down, then about 5 seconds later upshifts, and I'm on my way. Sometimes 5 times a day, sometimes 5 times a year.

Last week, started the truck and had a CEL, also had all gear positions lit on the dash. Weird. Truck drove fine, gear position thing fixed itself, CEL cleared after three key cycles, so I shrugged it off.

50 miles later, truck shifts itself D-N-D-N-D while I'm sitting with my foot on the brake and over the next 50 miles it won't stay in the selected gear, it won't fully engage 1st, it just doesn't work. P1698 has come and gone, truck won't move forward (reverse seems to work fine, maybe it's only mechanically controlled?), all gear positions are illuminated and when I try for a forward gear, I don't get the normal relay buzz that I'm used to as it pressurizes the clutch pack.

I figure that with no talking to the PCM and no talking to the transmission, the TCM is just out. 10 bucks for a replacement, no change at all. I've located every ground I'm aware of, all good. I swapped relay 31 as it was freaking out, no change. I checked "trans power" fuse, good. I checked wiring under the dash for anything obvious, no luck. I checked the big fat wire from the TCM to the PCM to the firewall, looks good. Pulled, and broke, all three PCM plugs. Everything seems in order. Pulled my line pressure modifying doodad, no change.

Engine runs like a top. Dash is normal other than what's coming from the trans. Battery is new.

Ideas? PS - 2000 4.7 2WD Ext Cab. Blue.
1 - 3 of 9 Posts
The P1698 code is mentioned in the 2000 Dodge Dakota Factory Service Manual, hope it helps.

See less See more
Mine is a PDF online version, but it should be exactly the same, 2129 pages.

Check section 25, pages 14 & 15.
I added a link to the 2000 Dodge Dakota Service Manual HERE, it's a Free PDF file download.

It's great, you can simply do a quick search instead of looking through the book. After the quick download, just save it to your computer.
1 - 3 of 9 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.