U0100: Lost Communication with ECM/PCM
10 vehicles · 6 makes · $80-$3,500 repair
Most Reported On
U0100 is an OBD-II diagnostic trouble code meaning “Lost Communication with ECM/PCM.” U0100 is a network communication code meaning a module has lost communication with the engine control module / powertrain control module (ECM/PCM) over the vehicle's data bus. The ECM/PCM is the brain that runs the engine, so when other modules can no longer 'talk' to it, the effects can be serious — a no-start, stalling, multiple warning lights, and many other modules logging faults at once. This is almost always a wiring, connector, power/ground, or bus fault, or a failure of the ECM/PCM itself, rather than a single sensor. It should be diagnosed promptly because the vehicle may be undrivable. This code is most commonly reported on 2011-2013 Ford Fusion, 2000-2008 Jaguar S-TYPE, and 2021-2026 Audi Q5 Sportback (Premium, Premium Plus, Prestige), plus 7 other vehicles, with repair costs ranging from $80 to $3,500.
Common Causes
Typical Repair Cost
Based on 12 documented vehicle-specific issues. Actual cost depends on root cause and vehicle.
Diagnostic Tools
To diagnose U0100, you'll need an OBD-II scanner. Here are our recommendations at every price point.
ANCEL AD310 Classic OBD-II Scanner
by ANCEL
A simple, affordable code reader that reads and clears check engine codes. Great for quick diagnostics on any OBD-II vehicle (1996+).
- Read & clear engine codes
- View freeze frame data
- I/M readiness status
- No batteries or app needed
BlueDriver Pro Bluetooth Scanner
by BlueDriver
Bluetooth OBD-II scanner with a free companion app. Provides enhanced diagnostics, smog readiness, and repair reports sourced from a database of verified fixes.
- Enhanced diagnostics (ABS, SRS, transmission)
- Repair Reports with verified fixes
- Smog check readiness
- Free app (iOS & Android)
LAUNCH CRP123X OBD-II Scanner
by LAUNCH
A professional-grade handheld scanner that reads all four major systems (engine, transmission, ABS, SRS) with live data streaming and graphing.
- Engine, transmission, ABS, SRS diagnostics
- Live data stream & graphing
- AutoVIN for vehicle identification
- Free lifetime updates via Wi-Fi
Autel MaxiCOM MK808S Diagnostic Tool
by Autel
Shop-level diagnostic tablet with bi-directional control, active tests, and full system coverage. Ideal for serious DIYers and small shops.
- All-system diagnostics (25+ modules)
- Bi-directional control & active tests
- Oil reset, EPB, BMS, TPMS, injector coding
- 7-inch touchscreen with Android OS
As an Amazon Associate, we earn from qualifying purchases. Prices are approximate and may vary.
Vehicles Affected (10)
Electric Power Steering Rack Failure (Recall 15V340)
Instrument Cluster / Speedometer Erratic Readings and Gauge Dropout
Electric Power Steering (EPAS) Assist Loss / Steering Fault Warnings
12V Battery Drain Causing No-Start and Dead Vehicle
Trailer brake controller / integrated trailer brake module malfunction
Electric power steering (EPS) assist loss / reduced assist warnings (new body style)
Multiple Warning Lights with Speed Limited to 36 MPH
FAQ
What does U0100 mean?
U0100 stands for "Lost Communication with ECM/PCM." U0100 is a network communication code meaning a module has lost communication with the engine control module / powertrain control module (ECM/PCM) over the vehicle's data bus. The ECM/PCM is the brain that runs the engine, so when other modules can no longer 'talk' to it, the effects can be serious — a no-start, stalling, multiple warning lights, and many other modules logging faults at once. This is almost always a wiring, connector, power/ground, or bus fault, or a failure of the ECM/PCM itself, rather than a single sensor. It should be diagnosed promptly because the vehicle may be undrivable.
What are the most common causes of U0100?
The most common causes of U0100 are: Loss of power or ground to the ECM/PCM, CAN bus wiring damage, short, or open circuit, Corroded, loose, or damaged connectors at the module, Blown fuse feeding the ECM/PCM, Failed ECM/PCM, Another faulty module pulling down the data bus, Water intrusion or corrosion in a connector/harness. The specific cause varies by vehicle.
How much does it cost to fix U0100?
Repair costs for U0100 range from $80 to $3,500, depending on the vehicle and root cause.
Which vehicles are affected by U0100?
Au7o has documented U0100 across 10 vehicle models from 6 manufacturers: Audi, Chevrolet, Ford, GMC, Jaguar, Jeep.
Sources (12)
- mediaFord Preliminary Evaluation PE14030: EPS failure 2010 Fusion - CarComplaints
- media2010 Ford Fusion Power Steering Assist Fault - CarComplaints
- ForumSilveradoSierra: 2024 HD Trailer Brakes Disconnecting
- ForumGM-Trucks: 2024 Brake controller Problems
- ForumGrand Design Owners: Brake controller issues on 2024 GM HD trucks
- ForumDuramax Forum: 2024 HD trailer brake controller recall
- ForumSilveradoSierra: Electric Power Steering
- mediaZehl & Associates: 800,000 Chevrolet Silverado and GMC Sierra Trucks for Faulty Power Steering
- mediaAboutLawsuits: GMC Sierra, Chevy Silverado Recall Issued Due to Electric Power Steering Problems
- ForumSilveradoSierra: Loss of all power steering 2019 sierra elevation 5.3
- owner-reportCarComplaints.com — Ford Transit problem listings (owner-reported issues; check steering/EPS-related entries by model year)
- owner-reportHummer EV System Issues — HummerChat.com
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.