System: Network (U-Code)
SAE Standard (Generic)
Family: Lost Comm Powertrain Module
Code U0101: Lost Communication With TCM
Diagnostic & Technical Explanation
U0101 sets when the gateway or another control module stops receiving any messages from a powertrain-side module or smart sensor -- the ECM/PCM, TCM, or one of the engine-bay LIN-networked sensors (MAP, MAF, EGR, turbo boost, fuel pressure, and similar) that report over a low-speed sub-bus feeding into the high-speed backbone. These nodes live in the engine compartment where connectors see more heat-cycling, vibration, and oil/coolant contamination than any other module class, so a burned or corroded engine-harness connector is the leading cause, followed by a blown fuse for that module's dedicated power circuit.
First-listed procedure
Rank #1
Check the module's dedicated fuse and battery/ground connections
Easy DIY
This is the first procedure in the authored
consideration order, not a measured cause likelihood. Execute it only when its prerequisites
and diagnostic findings support it. Its cost and labor estimates (where known), the step-by-step procedure and the
remaining 3 procedure(s) are in the licensed dataset. Ordering context.
Full family: Lost Comm Powertrain Module
What this page does not show
This page publishes the fault mechanism and the code index. The licensed dataset adds, for
every one of the 15,886 codes, the full authored repair set (56,729 procedures in total)
with the fields deliberately withheld here:
- Procedures 2..n after the first-listed procedure
- Aftermarket parts cost ranges in USD (
est_parts_cost_min/max_usd)
- Professional labor-hour estimates (
est_labor_hours)
- Step-by-step diagnostic and repair instructions
- Replacement-part mappings and catalog lookups
- 6,637 manufacturer-specific OEM codes across 32 makes ($149 tier)