U351AHigh Voltage System Interlock Circuit D Performance
- Generic OBD-II code · Network
- Turns on the check-engine light
- Can trigger limp mode
- How the car detects it
- U351A says that loop D returns a signal, but not the one the module sent out. Many designs feed the loop with pulses rather than a steady level. In a Corun battery patent a microcontroller sends a 0 to 5 V square wave at 100 Hz with half on, half off through the interlock switches of pack, motor controller and vehicle controller, and treats the loop as sound only if frequency, on-time and amplitude return unchanged. A rounded, shifted or weakened pattern hints at contact resistance, moisture or coupled interference rather than a clean break. No maker documents U351A. High voltage may drop out without warning.
- What you may notice
- Sudden loss of high-voltage power while driving or charging
- Fault appears after rain, washing or on rough roads
- Restart sometimes possible after switching off and on
- Likely causes
- LikelyCorroded or worn interlock contacts adding resistance to loop D
- PossibleMoisture in a low-voltage connector of the loop
- RareLoop wiring routed too close to switching high-voltage cables
- RareSignal input of the evaluating controller faulty
- Repair
- Hard · Usually a job for a workshop.Typical cost: €100 – €1,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.