U3529High Voltage System Interlock Circuit H
- Generic OBD-II code · Network
- Turns on the check-engine light
- Can trigger limp mode
- How the car detects it
- U3529 marks a fault on circuit H, the eighth interlock loop, without a more specific result. Texas Instruments distinguishes one central loop running through all high-voltage parts from individual loops inside each subsystem that confirm its own assembly. Eight separate loops are realistic mainly for trucks, buses and machines with several packs and distribution boxes, such as Volvo's electric-road trucks with at least two HV buses or Caterpillar's multi-pack machines; in passenger cars a fourth to eighth loop is hardly to be expected. No manufacturer documents U3529. On a car, compare codes in other units before assuming a wiring fault.
- What you may notice
- One HV branch or pack unavailable, or no ready mode
- Warning about the high-voltage system
- Likely causes
- LikelyConnector or disconnect on loop H open
- PossibleLoop H wiring damaged on chassis or between packs
- RareCode logged by a controller with faulty software rather than a real loop H fault
- 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.