08/22/2026
PSA.
Working on a 2015 Jeep Grand Cherokee with an 8 speed automatic transmission recently and discovered something very interesting.
First. The transmission acted up doing 80mph, threw the vehicle into "limp" mode and displayed a message saying "service transmission immediately ". Shortly after that, the vehicle display read "do not shut off" and once the vehicle was shut down, it thought it was in gear still and wouldn't restart.
After resetting the ECU and TCM, there was zero improvement. Pulling and replacing the TCM fuse helped because it was blown and needed replaced. This enabled codes to be cleared, the vehicle to start, run and move under its own power but just briefly. Messages and codes came back within 2 minutes of use.
Now I'll explain the pictures and why they aren't of a transmission. I was 99% sure this was an electronic issue outside the transmission itself by the systems so I started digging in and reading.
Upon reading some jeep white papers I found that the CAN bus is connected to EVERYTHING. Nothing separate for powertrain but every electronic module all on 1.
After looking around, I noticed this tray completely full of loose change and a quarter, along with a dime on top, had made thier way into the SD card port. Since the infotainment system runs through the single affor mentioned CAN bus, it seemed logical to at least try and remove the coins, replace the newly replaced, and newly blown TCM fuse. Cleared the codes again and after 2 days off and on driving in all conditions. Still zero issues with the vehicle at all. If you're like me and don't like change in your pockets, try and avoid putting it anywhere near any opening where a coin might slide into on accident.
Also. If you experience this and a transmission shop says you need a new transmission. Get a 2nd opinion first.
