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Discussion Starter · #1 · (Edited)
Sorry for starting a new thread, I tried to revive some old ones, no luck.

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.
 

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Discussion Starter · #2 ·
How about my solenoid pack, could it be the issue? I pulled it a few years back and metered all the connections, they were all within spec, but I know that thing goes bad. I do have the original, faulty design.
 

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Discussion Starter · #3 ·
I checked the continuum transfunctioner today, no issues there. Anyone have any other ideas?
 

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C'mon Dodge - NEW DAKOTA
2003 Dakota Club Cab Sport 4.7L
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Check your turboencabulator .
 

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Sorry for starting a new thread, I tried to revive some old ones, no luck.

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.
Mopar likes to power the TCM relay from the return power that excites the alternator, check for power on both wires on the small plug on the alternator, one comes from the PCM to excite the stator and the other comes back out to power the TCM relay. But they usually will move forward but in 2nd gear only. I ran into this on my 2000 Durango and I know my 2001 caravan is the same. And on mine the return wire was shorted out in the brush holder so the alternator still charged because the circuit was complete but not grounding in the right spot. Put a new brush holder in it and it works fine.
 

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Discussion Starter · #8 ·
Ok, thanks, I'll check that out. ~12V at both and I'm guessing it needs to be running to see voltage on both sides?
 

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Discussion Starter · #9 · (Edited)
Here's what I got:
13.75VDC at the alternator post and the battery. Seems low to me, I'm used to 14.5ish, but this seems to have changed over the years and is no longer standard alternator output.
13.75VDC at the passenger side small wire going into the back of the alternator, both plugged in and unplugged.
9.8 to 10.8VDC at the driver's side small wire while plugged in, depending on how my probe landed in there
0VDC at the driver's side unplugged. When I plugged it back in, I heard the engine load as the alternator started making power.

Is -3VDC enough to cause the TCM to act up?

More info: My neighbor has the fancy scanner that can talk to the TCM. Except it can't, it's not there. We bypassed the relay that turns it on, and it's still not there. He's thinking that it has no power. I'm going to find a pinout and see if we can determine that there's no 12VDC to the TCM or if it's truly a buss issue. I'm also going to put the original replacement TCM in since it worked fine for a few years. No idea if the ebay TCM is even good.

More More info, can't find a pinout, and there isn't one in my Chilton manual. Anyone have a link or PDF?
 

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Discussion Starter · #10 ·
Anyone know of a pinout for the TCM? I have one for the solenoid pack, but it doesn't link to a more in depth one.
 
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