What does this code mean?
A reporting module did not receive expected messages from the engine/powertrain controller. Record which modules report U0100 and which still communicate. Battery voltage, power supplies, grounds, connectors and network wiring should be tested before condemning a controller. The reporting module is not necessarily the failed module.
Sources and interpretation [1]
A code identifies a detected condition, not a part that must automatically be replaced.
Manufacturer communications
3Original wording in English
CADILLAC
Reported code forms U0100
This Preliminary Information communication provides information to the technician about vehicles with the Service Engine Soon light is on, Reduced engine power message, no crank, multiple warning lights on, transmission…
CADILLAC
Reported code forms U0100
This Preliminary Information communication provides information to the technician about vehicles with the Service Engine Soon light is on, Reduced engine power message, no crank, multiple warning lights on, transmission…
CADILLAC
Reported code forms U0100
This Preliminary Information communication provides information to the technician about vehicles with the Service Engine Soon light is on, Reduced engine power message, no crank, multiple warning lights on, transmission…
Check vehicle applicability
6A listed vehicle is a research lead. Confirm the engine, production range and software in the manufacturer's information.
Historical vehicle association; OBD-II compatibility is not established by this record.
| Make | Model | Model year |
|---|---|---|
| Cadillac | STS | 2011 |
| Cadillac | STS | 2010 |
| Cadillac | STS | 2009 |
| Cadillac | STS | 2008 |
| Cadillac | STS | 2007 |
| Cadillac | STS | 2006 |
Historical records · 1 · Historical vehicle association; OBD-II compatibility is not established by this record.
Before replacing a part
Record codes and freeze-frame data. Check battery condition, related codes and visible wiring or hose damage. Follow the vehicle's diagnostic procedure and test results before replacing parts.
Sources and interpretation
These explanations are editorial summaries of the linked manufacturer material. PDF page numbers count from the first file page. Original publications are in English; translations are reference aids. A cited edition is not a claim that it is the manufacturer's latest instruction.
- Audi TT Quick Reference Specification Book · October 2013 ↗
Audi of America · PDF page(s) 143 ·
- 01-19-05TT / 2054867/7 · No start or ECM communication, U0100 ↗
Volkswagen Group of America · PDF page(s) 1, 2 ·
Source check date · 2026-10-27
Can I keep driving?
A code alone cannot establish whether driving is safe. A flashing malfunction light, severe shaking, overheating, oil-pressure warning or loss of braking or steering needs prompt attention. Stop in a safe place and seek assistance when control or engine safety is affected. Follow the vehicle handbook.