U0101 — Lost Communication with TCM
What it means: Lost Communication with TCM.
How serious / can you keep driving: Serious. Power derate likely — plan to stop soon.
Check first: Start with the most likely cause: TCM power loss.
Don't risk it — look up listed providers near you and give them this code when you call.
Listed providers nearest Houston, TX
Closest first. Tell them U0101 and what the truck is doing. RoadService.app lists these providers and does not employ them or carry out the repair.
- 0.0 mi away — based in Houston, TX · (832) 377-0578
- 0.0 mi away — based in Houston, TX · (713) 219-9090
- 0.0 mi away — based in Houston, TX · (713) 671-9751
Seen on: All trucks with automatic trans
What U0101 means
Lost Communication with TCM. Common causes: TCM power loss, CAN wiring fault.
How serious is it?
Serious. Power derate likely — plan to stop soon.
Most likely causes
- TCM power loss
- CAN wiring fault
- J1939 terminator missing
- TCM failure
FAQ
Lost Communication with TCM. Common causes: TCM power loss, CAN wiring fault.
Serious — Power derate likely — plan to stop soon.
The most common cause is: TCM power loss. Other possibilities include CAN wiring fault; J1939 terminator missing; TCM failure.
Power derate likely — plan to stop soon. When in doubt, get a qualified mobile diesel tech on the truck before continuing.
Related codes
Codes that commonly appear alongside U0101, or share the same subsystem.
- ECU Power Supply — Intermittent / Erratic (SPN 627 FMI 2)
- Battery / Charging Voltage — Low (SPN 168 FMI 18)
- Engine Controller (ECM) — Internal Fault (SPN 629 FMI 12)
- Battery voltage low during crank (SPN 168 FMI 17)
- J1939 proprietary datalink lost (SPN 625 FMI 9)
- J1939 Data Link — Communication Error (SPN 639 FMI 2)
- High Speed CAN Bus Fault (U0001)
- Lost Communication with ECM/PCM (U0100)
Same symptom: Lost communication
Other datalink faults. A U-code is a network problem and is diagnosed at the datalink, not at the module that went quiet.
- Lost Communication with Fuel Injector Control Module (U0105) · Electrical, Charging & Network
- Lost Communication with Gear Shift Module (U0103) · Electrical, Charging & Network
- Lost comms with ABS (U0121) · Electrical, Charging & Network
- Lost Communication with Body Control Module (U0140) · Electrical, Charging & Network
- Invalid Data from ECM (U0401) · Electrical, Charging & Network
- Invalid Data from TCM (U0402) · Electrical, Charging & Network
Find a mechanic or related guides
General diagnostic guidance for diesel engines (Cummins, Detroit, PACCAR, Volvo, Mack and more). Not a substitute for a scan-tool diagnosis on your specific truck.