U0100: Lost Communication with ECM/PCM
16 vehicles · 9 makes
U0100 is an OBD-II diagnostic trouble code meaning “Lost Communication with ECM/PCM.” A module has lost communication with the engine control module. Can cause no-start or reduced functionality. This code appears across 16 vehicle models from 9 manufacturers.
Common Causes
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
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Vehicles Affected (16)
Electric Power Steering Rack and Gear Failure
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." A module has lost communication with the engine control module. Can cause no-start or reduced functionality.
What are the most common causes of U0100?
The most common causes of U0100 are: ECM/PCM failure, CAN bus wiring fault, ECM power supply issue, Corroded connector, Ground fault at ECM. The specific cause varies by vehicle.
How much does it cost to fix U0100?
Repair costs vary widely depending on the root cause and vehicle.
Which vehicles are affected by U0100?
Au7o has documented U0100 across 16 vehicle models from 9 manufacturers: Alfa Romeo, Audi, Chevrolet, Ford, GMC, Jaguar, Jeep, Mercedes-Benz, Subaru.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.