U3514High Voltage System Interlock Circuit B High
- Generic OBD-II code · Network
- Turns on the check-engine light
- Can trigger limp mode
- How the car detects it
- U3514 means loop B reads higher than allowed: a wire of the loop touches 12 V or another supply, or the loop does not fall back to its low state once the module turns its source off. GM's loop A code checks both states, allowing 24 % of 5 V while the source is off and 44 % while it is on. Ford's interlock patent tests the source line for a short to 12 V before releasing the loop, then stores a trouble code and turns on the Service Soon lamp rather than a general warning. In the reference design from Texas Instruments a short to battery shows up as loop current that no longer follows the commanded on/off pattern. No manufacturer lists U3514 itself. Disconnecting segments one at a time shows where the foreign voltage enters loop B.
- What you may notice
- Vehicle will not start or enter ready mode
- Service or HV warning lamp on
- Fault stays present with all HV connectors properly mated
- Likely causes
- LikelyInterlock wire of loop B shorted to 12 V or another supply
- PossibleInterlock source in the module not switching off
- PossibleWater in a connector bridging an interlock pin to a supply pin
- RareIncorrect splice or add-on wiring after a repair
- Repair
- Hard · Usually a job for a workshop.Typical cost: €80 – €1,200
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.