U351BHigh Voltage System Interlock Circuit D Low
- Generic OBD-II code · Network
- Turns on the check-engine light
- Can trigger limp mode
- How the car detects it
- U351B reports that too little level comes back from interlock loop D while the module drives it. GM's hybrid tables for the loop A code P0A0C give a frame of reference: the test only runs when on-board voltage exceeds 10.2 V, judges what fraction of a 5 V test signal returns against a 30 % limit and logs a Type A fault after two failed 12.5 ms readings. A weak 12 V battery thus pauses the check instead of tripping it. No maker publishes a calibration for U351B. Typical causes are a wire crushed against the body, a loop plug left off, or a dead source; the contactors behind loop D may not close.
- What you may notice
- No ready mode or high-voltage branch D unavailable
- Warning to have the high-voltage system checked
- Fault stays present after clearing until the wiring is repaired
- Likely causes
- LikelyLoop D wire pinched against the body and shorted to ground
- PossiblePlug within loop D not seated after a repair
- RareTest voltage source in the controller failed
- 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.