A receiving module detected implausible data from the digital tachograph module (commercial vehicle driving-time recorder). Speed, distance or driver-card values fail plausibility checks and are rejected.
Medium severity. Can I keep driving?It depends on which control module has dropped out. If it affects the engine, brakes, or steering, do not continue your trip: call for roadside assistance.
Symptoms
- Multiple warning lights may illuminate
- Affected modules may go into limp mode or shut down
- Specific functions inoperative depending on module
- Diagnostic tools may show communication faults
Most likely causes
- Module internal fault or sensor input drift
- Software version mismatch after replacement
- Gateway module routing CAN messages incorrectly
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: medium
What each character of U049B means
- U: Communication network
- 0: Generic code: same on every make
- 4: Subsystem depends on the code range
- 9B: Specific fault in that system
Frequently asked questions
Can I keep driving with code U049B?
It depends on which control module has dropped out. If it affects the engine, brakes, or steering, do not continue your trip: call for roadside assistance.
What causes code U049B?
The most common causes are: module internal fault or sensor input drift; software version mismatch after replacement; gateway module routing CAN messages incorrectly.
Sources
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.