Public Service Announcement: Replace Thy Battery if Trans Codes Appear

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Overlander

Senior Member
Joined
Sep 12, 2020
Posts
370
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Location
Oregon
Ram Year
2021 75th Aniv Build #0006
Engine
6.4 Hemi
Condition:
2021 2500 6.4 Power Wagon. Cold morning (22F) start last week was fine. Vehicle warmed in driveway for 10 minutes before driving. Within 100 yards service transmission message and MIL on the dash. Truck would not shift out of first. Pulled into the first side street, shut off vehicle and restarted. Vehicle shifted fine but dash indicators remained. Code on old Craftsman scan tool was P0731. Could not clear code. Left vehicle parked in driveway and took another truck on the trip.

Returned three days later and no MIL and vehicle shifted fine. New scan tool (OBDLink MX+) showed additional C2226 and canbus codes.

Cause:
The TCM and canbus codes led me to believe this wasn't a mechanical failure but electronic in nature. In research I had found a similar post from the Jeep world where a defective battery was the cause. This seemed plausible as it was a slow crank that day. I'm guessing voltage dropped below threshold and caused the TCM to error.

Correction:
Replaced the battery with Napa Legend 94R.

Confirmation:
Vehicle now spins much faster on cold start crank. Zero errors since. While the batt was only 3 years old, I believe it was showing wear and when strained could no longer keep the electronics happy on cold start. Have a 400 mile trip here in a few days and will verify that the 'fix' works.

As a side note, Uconnect isn't happy when the battery is removed. Some people use a battery tender to keep things 'alive' while the batt is out. Mine is a 'overlander' build and I had a number of disconnected wires to other circuits under the hood and didn't want to take the time to tape all those off or risk a short. When the battery is reconnected two things will happen: 1) the doors will lock. So make sure keys aren't in the vehicle. 2) uconnect will show the anti-theft code. The code goes away upon vehicle start, but not all Uconnect modules are avialble. The fix to close the door, turn the vehicle to run (without starting ) hold down tune and volume knobs for 30 sec. Release. Turn vehilce off. Open the door. Close door and start vehicle. All systems should come back.
 

Tulecreeper

Senior Member
Military
Joined
May 27, 2023
Posts
1,683
Reaction score
1,807
Location
Wstrn AR
Ram Year
2023
Engine
6.4 Hemi
Condition:
2021 2500 6.4 Power Wagon. Cold morning (22F) start last week was fine. Vehicle warmed in driveway for 10 minutes before driving. Within 100 yards service transmission message and MIL on the dash. Truck would not shift out of first. Pulled into the first side street, shut off vehicle and restarted. Vehicle shifted fine but dash indicators remained. Code on old Craftsman scan tool was P0731. Could not clear code. Left vehicle parked in driveway and took another truck on the trip.

Returned three days later and no MIL and vehicle shifted fine. New scan tool (OBDLink MX+) showed additional C2226 and canbus codes.

Cause:
The TCM and canbus codes led me to believe this wasn't a mechanical failure but electronic in nature. In research I had found a similar post from the Jeep world where a defective battery was the cause. This seemed plausible as it was a slow crank that day. I'm guessing voltage dropped below threshold and caused the TCM to error.

Correction:
Replaced the battery with Napa Legend 94R.

Confirmation:
Vehicle now spins much faster on cold start crank. Zero errors since. While the batt was only 3 years old, I believe it was showing wear and when strained could no longer keep the electronics happy on cold start. Have a 400 mile trip here in a few days and will verify that the 'fix' works.

As a side note, Uconnect isn't happy when the battery is removed. Some people use a battery tender to keep things 'alive' while the batt is out. Mine is a 'overlander' build and I had a number of disconnected wires to other circuits under the hood and didn't want to take the time to tape all those off or risk a short. When the battery is reconnected two things will happen: 1) the doors will lock. So make sure keys aren't in the vehicle.
Not on mine. ;)
 

Tulecreeper

Senior Member
Military
Joined
May 27, 2023
Posts
1,683
Reaction score
1,807
Location
Wstrn AR
Ram Year
2023
Engine
6.4 Hemi
What was the cause / repair?
I was making a joke. Mine won't automatically lock the doors because I have manual locks...and windows...and seats, etc. I ordered mine with as few options as I could because I don't want nor need all the electronic nightmares.
 
OP
OP
Overlander

Overlander

Senior Member
Joined
Sep 12, 2020
Posts
370
Reaction score
532
Location
Oregon
Ram Year
2021 75th Aniv Build #0006
Engine
6.4 Hemi
I was making a joke. Mine won't automatically lock the doors because I have manual locks...and windows...and seats, etc. I ordered mine with as few options as I could because I don't want nor need all the electronic nightmares.
Gotcha, lol.
 
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