RAM ZF 8 Speed Transmission Control Module Log/Error Code Storage

[maverickd9]

BLUF - If I had a warning message show up on the instrument display of my 2023 Ram 2500 with the ZF transmission stating "Service Transmission", how long is that log maintained in the TCM?

Explanation

I have a 2023 Ram 2500 Big Horn with the 6.4l/ZF transmission. Currently has just over 16,000 miles. Last weekend I was driving to Lake Tahoe with my wife and son. We were on a 2 lane mountain highway that was dry, but the side of the road were banked with snow. I crested a hill and saw a downhill section, so I engaged the ERS mode on the steering wheel. Immediately, the instrument displayed a "Service Transmission" message which could not be cleared, and the truck would not downshift from 7th gear. I used the brakes to control my speed down the hill, and began looking for a place to safely pull off the highway. Due to the snow, there were no spots, and I reached the bottom of the hill and started climbing in 7th gear. Luckily the truck had enough power to get up part of the hill to a pull-off.

There, I was able to place the vehicle in park, shut the truck off, restart, and the problem went away. The rest of the trip was uneventful, and upon returning home, I booked an appointment with the local dealer to look at the issue. I dropped the truck off, and waited 2 days with no contact from the dealer. I finally reached out this morning, and they said there were no codes stored in the TCM, and the truck was fine.

I'm skeptical that a warning could be displayed but not stored regarding this issue. Any insights on the TCM from more experienced folks? Also, anyone have any similar symptoms and find an issue? I'm planning to tow cross-country in a few months for a PCS move, and don't want to have issues because a dealer didn't know how to troubleshoot an issue. I've got other gripes with the dealership regarding labor charges for warranty inspection, and a very poor problem write-up by the service writer, but I'll address those with the service manager in-person.

 

[areuriding]

I've had warning lights with no codes before and not just with RAM, FORD as well. I can't explain it but it has happened. A couple of times were just weird glitches that never came back, but other times I would have a light on and off a few times before it would finally be stored. Best advice is wait until it is constantly on and then take it in and show them while it's actively on. PITA I know, but sometimes it's the only way..

 

[Bryanc81]

I had a similar issue with my truck. This last weekend towing home our toy hauler. I made it about two hours and the service transmission light came on. Shut it off and about 20 minutes later the truck worked fine. I ended up having somebody else tow my trailer home. I was not sure if something was wrong with the Trans. I drove the truck home without a load with no issues the dealer is little to no help and they are weak out on getting my truck in have you had any issues since. We have a trip planned next week that I have to use my truck.

 

[maverickd9]

My dealer wasn't able to find any issues. The transmission didn't have any stored warnings, which I would think is odd for a dash warning to to store.

My best theory is that the driving conditions caused a momentary issue in the valve body, such as lateral G's on the mountain turns, or negative G's from cresting a hill. This caused a temporary issue, and the trans threw the warning and refused to shift as a self-protective measure. I have no technical notes on my theory, just assumptions based of software logic and valve body knowledge.

I've driven a few hundred miles since without any issues, but no mountain driving or towing.

 

[Bryanc81]

OK, thanks for the quick reply. I have an appointment tomorrow with the dealer. They are going to scan it to see if mine stored any codes. If there are any codes found, I will post them on here to let you know. Mine actually happened when I was going downhill and my transmission temperature was 180.

 

[Bryanc81]

So I took my truck to the dealer and to no surprise there were no codes. I took my trailer on a test run this morning climbed about 3500 feet. One thing I did notice coming down the hill the transmission would shift extremely low throwing me to 5000+ RPM. I was trying to keep my speed around 35 to 40 mph going downhill. Fairly curvy climb did not want to go too fast.

We are leaving for a trip tomorrow so fingers crossed I don’t have an issue, but I do have a Bluetooth OBD reader. I will try to capture some codes if something happens.

 

[Bryanc81]

Trip is done and no issues. We will see!!!

 

[maverickd9]

Earlier this week I experienced the same failure as before, downhill grade, trying to bump ERS down to 5th gear from 7th. Saw RPMs jump, then return to 7th gear level, and Service Transmission in Dash. Very little power once off the hill, turning the truck off and on cleared the issue.

Happened about 100 miles west of Grand Junction CO in Utah. Took it to Grand Junction CDJR, and they were able to replicate and hopefully correct with a TSB fix.

TSB 21-002-24.
TCM reset and software update.

I find it annoying that the other dealer was unable/unwilling to do anything to the truck, especially with the TSB out since early last year.

I'll attach the document, and we'll see if there any issues returning to California.