U353BHigh Voltage System Interlock Circuit M Low
- Generic OBD-II code · Network
- Turns on the check-engine light
- Can trigger limp mode
- How the car detects it
- U353B is set when loop M reads too low. A lever-type plug can leave it in exactly that state on purpose. A connector patent by Hyundai and Kia adds an intermediate lock to the lever: on the way out it stops at a point where the interlock contacts are already apart while the power terminals still touch, so the system has time to switch off before the second lever movement separates the plug. If such a plug is left at the intermediate stage after service, or not pushed fully home, loop M stays open although the plug seems attached. Check every lever on the loop for its final locked position. No maker documents U353B; the contactors remain open.
- What you may notice
- No ready mode after service on high-voltage plugs
- Fault persists after clearing
- Likely causes
- LikelyLever-type connector in loop M left at its intermediate position
- PossibleLoop M wire shorted to ground
- RareLoop M source in the controller failed
- Repair
- Hard · Usually a job for a workshop.Typical cost: €60 – €1,200
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.