U0100

High Severity

Lost Communication with ECM/PCM

Network/Communication System

What Does U0100 Mean?

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

Common Fix

Repair CAN bus wiring or replace ECM

Estimated Cost (DIY)

$0 - $800

Symptoms

  • ⚠️Multiple warning lights
  • ⚠️No start
  • ⚠️Various systems not working
  • ⚠️Scan tool cannot connect to ECM

Related Symptoms

Car won't start

Common Causes

CAN bus wiring issuelikely
Faulty ECMpossible
Blown ECM fusepossible
Corroded connectorpossible

How to Diagnose U0100

  1. 1Check ECM fuses
  2. 2Check CAN bus wiring
  3. 3Inspect ECM connectors
  4. 4Test CAN bus communication

OEM Diagnostic Flowchart

Scroll to load technician if/then branches.

U0100 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 U0100.

OEM Manual Evidence

Browse →
2013 GMC Truck Acadia FWD V6-3.6L A L L Diagnostic Trouble Codes ( DTC )OEM Manual

A L L Diagnostic Trouble Codes ( DTC ) — 2013 GMC Truck Acadia FWD V6-3.6L Service Manual | Operation CHARM Operation CHARM : Car repair ma...

2013 GMC Truck Acadia AWD V6-3.6L A L L Diagnostic Trouble Codes ( DTC )OEM Manual

A L L Diagnostic Trouble Codes ( DTC ) — 2013 GMC Truck Acadia AWD V6-3.6L Service Manual | Operation CHARM Operation CHARM : Car repair ma...

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 Chevy Truck Traverse AWD V6-3.6L A L L Diagnostic Trouble Codes ( DTC )OEM Manual

A L L Diagnostic Trouble Codes ( DTC ) — 2013 Chevy Truck Traverse AWD V6-3.6L Service Manual | Operation CHARM Operation CHARM : Car repai...

Related Symptoms

Browse →
Car won't startSymptom Hub

No-crank and no-start complaints usually resolve into battery, starter, alternator, crank sensor, or fuel-delivery diagnosis.

Exact Vehicle Hubs

Browse →
2013 Chevy Truck Traverse Awd V6 3.6l Repair HubManual

Open the exact vehicle hub grounded by OEM manual evidence related to U0100.

2013 Gmc Truck Acadia Awd V6 3.6l Repair HubManual

Open the exact vehicle hub grounded by OEM manual evidence related to U0100.

2013 Gmc Truck Acadia Fwd V6 3.6l Repair HubManual

Open the exact vehicle hub grounded by OEM manual evidence related to U0100.

2013 Gmc Truck Savana 1500 Rwd V6 4.3l Repair HubManual

Open the exact vehicle hub grounded by OEM manual evidence related to U0100.

Related Codes

U0101: Lost Communication with TCMRelated

Communication lost between the ECM and transmission control module.

U0073: Control Module Communication Bus OffRelated

The entire CAN bus network has stopped communicating. Major system failure.

P0600: Serial Communication LinkRelated

Communication error within the ECM or between the ECM and scan tool.

Frequently Asked Questions

What is the CAN bus?
CAN bus is the communication network that lets all vehicle modules (ECM, TCM, ABS, etc.) talk to each other.
Can a loose connector cause U0100?
Yes — a corroded or loose connector at the ECM is a common cause. Check all ECM connectors first.

Need a diagnosis for your specific vehicle?

Start Free AI Diagnosis →

100% Free — No signup required