U0101

High Severity

Lost Communication with TCM

Network/Communication System

What Does U0101 Mean?

Communication lost between the ECM and transmission control module.

Common Fix

Repair wiring or replace TCM

Estimated Cost (DIY)

$0 - $600

Symptoms

  • ⚠️Transmission warning light
  • ⚠️No shifting or limp mode
  • ⚠️Check engine light
  • ⚠️Multiple codes

Related Symptoms

Check engine light on

Common Causes

CAN bus wiring faultlikely
Failed TCMpossible
TCM fuse blownpossible

How to Diagnose U0101

  1. 1Check TCM fuses
  2. 2Inspect CAN bus wiring
  3. 3Check TCM connectors

OEM Diagnostic Flowchart

Scroll to load technician if/then branches.

U0101 requires a scanner that reads network modules — basic code readers won't see it.

Recommended
TOPDON ArtiLink600

ArtiLink600

$99

DIYers working on ABS/airbag systems

View on TOPDON
TOPDON ArtiDiag900 Lite

ArtiDiag900 Lite

$299.24

Serious DIYers and side-hustle mechanics

View on TOPDON

Related Resources

Repair guides, symptom pages, and wiring diagrams related to U0101.

OEM Manual Evidence

Browse →
2013 GMC Truck Savana 1500 RWD V6-4.3L A L L Diagnostic Trouble Codes ( DTC )OEM Manual

A L L Diagnostic Trouble Codes ( DTC ) — 2013 GMC Truck Savana 1500 RWD V6-4.3L Service Manual | Operation CHARM Operation CHARM : Car repa...

2013 Subaru XV Crosstrek F4-2.0L DOHC A L L Diagnostic Trouble Codes ( DTC )OEM Manual

A L L Diagnostic Trouble Codes ( DTC ) — 2013 Subaru XV Crosstrek F4-2.0L DOHC Service Manual | Operation CHARM Operation CHARM : Car repai...

2013 Chevy Truck Captiva Sport FWD L4-2.4L A L L Diagnostic Trouble Codes ( DTC )OEM Manual

A L L Diagnostic Trouble Codes ( DTC ) — 2013 Chevy Truck Captiva Sport FWD L4-2.4L Service Manual | Operation CHARM Operation CHARM : Car...

2013 Chevy Truck Express 1500 RWD V6-4.3L A L L Diagnostic Trouble Codes ( DTC )OEM Manual

A L L Diagnostic Trouble Codes ( DTC ) — 2013 Chevy Truck Express 1500 RWD V6-4.3L Service Manual | Operation CHARM Operation CHARM : Car r...

Related Symptoms

Browse →
Check engine light onSymptom Hub

A check-engine light is a graph entry point into code pages, symptom-specific diagnosis, and the exact repair categories most often associated with those failures.

Exact Vehicle Hubs

Browse →
2013 Chevy Truck Captiva Sport Fwd L4 2.4l Repair HubManual

Open the exact vehicle hub grounded by OEM manual evidence related to U0101.

2013 Chevy Truck Express 1500 Rwd V6 4.3l Repair HubManual

Open the exact vehicle hub grounded by OEM manual evidence related to U0101.

2013 Gmc Truck Savana 1500 Rwd V6 4.3l Repair HubManual

Open the exact vehicle hub grounded by OEM manual evidence related to U0101.

2013 Subaru Xv Crosstrek F4 2.0l Dohc Repair HubManual

Open the exact vehicle hub grounded by OEM manual evidence related to U0101.

Related Codes

U0100: Lost Communication with ECM/PCMRelated

A module has lost CAN bus communication with the engine control module.

P0700: Transmission Control SystemRelated

The TCM (Transmission Control Module) has detected a fault and sent a message to the ECM. This is a general indicator that transmission-specific codes are stored.

Frequently Asked Questions

Will my car shift without the TCM?
The transmission enters limp mode — usually stuck in 3rd gear. Driveable but with limited function.
Can water damage the TCM?
Yes — on some vehicles the TCM is mounted low and can be damaged by flooding or deep water.

Need a diagnosis for your specific vehicle?

Start Free AI Diagnosis →

100% Free — No signup required