Network, generic (extended)
U353E High Voltage System Interlock Circuit N Performance
Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modePossible
U353E marks loop N as implausible. Such a verdict can stem from electrical interference rather than from the loop wiring. Tesla bulletin SB-25-17-005 for 2023 and 2024 Model Y cars describes the centre high mounted stop lamp disturbing the supply line of the high-voltage controller, which set HVIL alerts on an intact loop; the fix is a ferrite clipped around the thickest tan wire of that harness branch. A fault that coincides with braking or with other loads switching on suggests similar coupling on loop N. No maker documents U353E. Wiring checks then find nothing, and the warning may clear by itself.
Likely causes
Interference from another load coupling into the supply of the monitoring controller
Loose contact in a loop N connector
Ferrite or shielding missing after harness repair
Evaluation software of the controller too sensitive
Symptoms
- High-voltage warning that appears briefly, sometimes when braking
- No fault found on loop resistance checks
- Occasional refusal to become ready
Repair estimate
DifficultyHardWorkshop job
Parts and labour€50–800
Time0.5–3 h
Typical range across vehicles; the real cost depends on what the testing finds.
Parts involved
hvil loop n
Related codes
References: static.nhtsa.gov, law.cornell.edu.