U3519High Voltage System Interlock Circuit D
- Generic OBD-II code · Network
- Turns on the check-engine light
- Can trigger limp mode
- How the car detects it
- U3519 marks a fault on the fourth interlock loop of the high-voltage system, circuit D, that the module does not classify further. A fourth independent loop mainly makes sense where one vehicle carries several battery packs. Caterpillar explains why for battery-powered mining, building and farm machines: with only one loop, charging or servicing a single pack would cut off all of them, so each battery group is watched on its own and the charging port gets yet another loop. No manufacturer publishes which parts belong to loop D. The contactors guarded by it open, and the branch behind them stays unavailable.
- What you may notice
- One battery pack or high-voltage branch not available
- Reduced range or power, or no ready mode at all, depending on design
- High-voltage system warning in the instrument cluster
- Likely causes
- LikelyDisconnect of the battery group on loop D left open or not locked after charging or service
- PossibleConnector in loop D not fully latched
- PossibleLoop D wiring damaged between packs or distribution units
- RareController that drives and reads loop D faulty
- Repair
- Hard · Usually a job for a workshop.Typical cost: €80 – €1,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.