U351CHigh Voltage System Interlock Circuit D High
- Generic OBD-II code · Network
- Turns on the check-engine light
- Can trigger limp mode
- How the car detects it
- U351C is stored when loop D carries more voltage than its present state allows. GM's high check for loop A, P0A0D, shows why both states are tested: with the source commanded to 0 V, more than 24 % of 5 V counts as a failure, five times in eight samples; with the source at 5 V the limit is 44 %, four times in six. A loop that fails to fall when its source switches off reveals foreign voltage even if it looks normal while fed. No maker lists U351C. Likely are a loop wire touching a 12 V feed, a source that no longer turns off, or a bad repair splice. Readiness is withheld until the loop is clean.
- What you may notice
- Vehicle does not reach ready mode
- Fault returns immediately after clearing
- Other 12 V consumers may show faults if a supply wire is involved
- Likely causes
- LikelyLoop D wire in contact with a 12 V supply line
- PossibleSource driver in the controller no longer switches off
- RareEarlier repair splice joined the loop to a wrong wire
- 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.