U0100 on TOYOTA PRIUS
Lost Communication With ECM/PCM A
Methodology: Reviewed against the SAE J2012 generic DTC definition and NHTSA owner-complaint patterns, then scoped to Toyota Prius context without treating complaints as confirmed diagnoses.
Sources: SAE/OBD-II definitions, manufacturer service information, and public reliability reports (including NHTSA where applicable).
- SAE J2012 Diagnostic Trouble Code Definitions — Generic diagnostic trouble code definition reference for U0100.
- NHTSA recalls, complaints, and manufacturer communications — Used to check public owner complaint context, recall status, and safety-related manufacturer communications by VIN or vehicle.
Limits: Guidance is informational and may not match every model-year or revision. Confirm with the official manual and diagnostics before replacing parts. For safety-critical or electrical work, use a qualified technician.
What U0100 Means on Your TOYOTA PRIUS
U0100 is a diagnostic trouble code indicating: Lost Communication With ECM/PCM A. This code relates to the vehicle network, module communication, or data bus system. The vehicle's computer detected a condition outside normal operating parameters and stored this code.
Real TOYOTA PRIUS Owner Reports
Source: NHTSA Complaints Database
"Smog check failed because of obd bulb check failure and obdii failure. service fault codes are u0100 lost communication with ecm/pcm "a" and u0111 lost communication with battery energy control module "a." car only has 60,000 miles."
"Driving on sb hwy 35 at 74mph, master warning light came on and vehicle shut down, no electrical or engine control. pulled safely to shoulder of road. car would not restart. got out of car, locked car, unlocked car (toyota technician instructions), then car restarted."
All reports filed by vehicle owners directly with the U.S. Department of Transportation.
📊 Complaint Trend by Model Year
Common Causes on TOYOTA PRIUS
Based on NHTSA complaint component analysis for this vehicle.
What To Do Next
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1
Check for recalls on YOUR VIN
Go to nhtsa.gov/recalls and enter your VIN. If your vehicle is covered, repairs are free.
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2
Get a proper diagnosis
A code alone doesn't tell you the exact failed part. A diagnostic at a shop ($50–$150) pinpoints the root cause before you spend money on parts.
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3
Compare repair quotes
Get 2–3 quotes. Dealer vs. independent shop prices often differ 30–50% for the same repair.