OBD-II code · Network
U0299 Lost Communication With DC/DC Converter Control Module B
The vehicle bus reports loss of communication with DC/DC converter module B. The converter that supplies the 12-V system from the high-voltage battery cannot be commanded; 12-V load shedding may begin.
Is it safe to drive with U0299?
The car may go into limp mode (reduced power). Get it diagnosed before a long trip.
Common causes
- Most likelyBus wiring open or shorted
- PossibleModule without power or ground
- PossibleModule failed
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
Repair at a glance
- Difficulty
- Hard
- DIY friendly
- Best left to a mechanic
- Typical labour
- 1–5 h
- Emissions test
- Usually unaffected
- After the fix
- A drive cycle is needed before the light stays off
- Parts involved
- Dc Dc Converter Module B, Vehicle Bus Wiring
Related codes
- U01BDLost Communication With DC/DC Converter Control Module C
- U0298Lost Communication With DC/DC Converter Control Module A
- U0296Lost Communication With AC/DC Converter Control Module A
- U0297Lost Communication with Hybrid Powertrain Control Module
- U029ALost Communication With Hybrid/EV Battery Pack Sensor Module
- U029BLost Communication With Drive Motor Control Module C
- U029CLost Communication With Drive Motor Control Module D
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.