OBD · Communication network
U0100 Lost communication with ECM/PCM
What this code means
U0100 is a generic OBD code shared by all manufacturers since 2001 for petrol and 2004 for diesel. It relates to: communication network. The code tells you what the ECU measured as abnormal, not necessarily which part to replace.
Most common causes
- Weak or dying battery#1
A battery over 5 years old that rests below 12.4 V is very likely the culprit.
Cost of related repairs
| Independent garage | Main dealer | |
|---|---|---|
| Car battery | £115 – £245 | £135 – £355 |
How to read this code
An OBD scanner plugged into the 16-pin socket under the steering wheel reads and clears codes. Bluetooth models cost £20 to £40. Clearing a code without fixing the fault is pointless: it comes back.
Related problems
Frequently asked questions
What does code U0100 mean?
U0100: Lost communication with ECM/PCM. U0100 is a generic OBD code shared by all manufacturers since 2001 for petrol and 2004 for diesel. It relates to: communication network. The code tells you what the ECU measured as abnormal, not necessarily which part to replace.
Can I drive with code U0100?
Fix soon. Drive gently and as little as possible. The fault can get worse and damage other parts.
How much does it cost to fix U0100?
Car battery: £115 – £245.
How to read this code
An OBD scanner plugged into the 16-pin socket under the steering wheel reads and clears codes. Bluetooth models cost £20 to £40. Clearing a code without fixing the fault is pointless: it comes back.