U3544High Voltage System Interlock Circuit O High
- Generic OBD-II code · Network
- Turns on the check-engine light
- Can trigger limp mode
- How the car detects it
- U3544 sets when loop O delivers too high a value. A plug can hold its specified torque and still sit crooked. FCA's STAR case S2108000121 (Rev. B, 2026) for Wrangler and Grand Cherokee 4xe models describes P0A0A after HV repairs although the connector bolts reached 9 Nm: the plug had gone on at an angle, the C3 connector of the power inverter module in particular. Three windows around its shield must show bare aluminium housing with no gap; spread interlock terminals mean replacing the HV component. In a current-fed loop such poor contact appears as a higher value. No maker documents U3544. Seat each plug squarely before tightening.
- What you may notice
- Check engine light and hybrid system message right after an HV repair
- No ready mode
- Likely causes
- LikelyHV plug on loop O torqued down while tilted
- PossibleInterlock terminals spread by a crooked fitting
- PossibleLoop O wire shorted to a 12 V feed
- RareConnector bolt thread stripped so the plug cannot be clamped
- Repair
- Hard · Usually a job for a workshop.Typical cost: €60 – €3,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.