U0100 on TOYOTA PRIUS — Lost Communication With ECM/PCM A

Q: "What does U0100 mean on a TOYOTA PRIUS?"

"U0100 indicates: Lost Communication With ECM/PCM A. This is a network communication code. 2 TOYOTA PRIUS owners have reported this to NHTSA."

Q: "What are the most common causes of U0100 on TOYOTA PRIUS?"

"Based on 2 NHTSA reports, the most commonly cited components are: Electrical System, Electrical System,Engine. These percentages are based on the component field in owner complaints."

Q: "Is U0100 serious on my TOYOTA PRIUS?"

"Of 2 NHTSA reports for this code on TOYOTA PRIUS, none involved a crash or fire. However, any diagnostic code should be evaluated by a qualified mechanic."

Q: "What should I do if my TOYOTA PRIUS shows U0100?"

"1) Check for recalls on your VIN at nhtsa.gov/recalls. 2) Get a professional diagnosis — a code alone doesn't identify the exact failed part. 3) Get 2-3 repair estimates to compare."

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 network communication system. The vehicle's computer detected a condition outside normal operating parameters and stored this code.

2 TOYOTA PRIUS owners have reported this issue to NHTSA across model years 2008. Most reports come from the 2008 model year. The most commonly reported component is Electrical System (50.0% of reports).

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."

— 2008 TOYOTA PRIUS owner · ELECTRICAL SYSTEM · Filed 03/21/2017

"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."

— 2008 TOYOTA PRIUS owner · ELECTRICAL SYSTEM,ENGINE · Filed 10/14/2014

All reports filed by vehicle owners directly with the U.S. Department of Transportation.

📊 Complaint Trend by Model Year

2

'08

Common Causes on TOYOTA PRIUS

Based on NHTSA complaint component analysis for this vehicle.

ELECTRICAL SYSTEM 50%

ELECTRICAL SYSTEM,ENGINE 50%

What To Do Next

1
Check for recalls on YOUR VIN
Go to nhtsa.gov/recalls and enter your VIN. If your vehicle is covered, repairs are free.
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.
3
Compare repair quotes
Get 2–3 quotes. Dealer vs. independent shop prices often differ 30–50% for the same repair.

Frequently Asked Questions

What does U0100 mean on a TOYOTA PRIUS? ▾

U0100 indicates: Lost Communication With ECM/PCM A. This is a network communication code. 2 TOYOTA PRIUS owners have reported this to NHTSA.

What are the most common causes of U0100 on TOYOTA PRIUS? ▾

Based on 2 NHTSA reports, the most commonly cited components are: Electrical System, Electrical System,Engine. These percentages are based on the component field in owner complaints.

Is U0100 serious on my TOYOTA PRIUS? ▾

Of 2 NHTSA reports for this code on TOYOTA PRIUS, none involved a crash or fire. However, any diagnostic code should be evaluated by a qualified mechanic.

What should I do if my TOYOTA PRIUS shows U0100? ▾

1) Check for recalls on your VIN at nhtsa.gov/recalls. 2) Get a professional diagnosis — a code alone doesn't identify the exact failed part. 3) Get 2-3 repair estimates to compare.