Network, generic (extended)

U353A High Voltage System Interlock Circuit M Performance

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

U353A flags loop M as questionable rather than plainly open or shorted. Redundant monitoring can produce exactly that state. NIO patented an interlock fed by two signal generators whose pulse trains overlap on one line; with duty ratios A and B the detector expects a combined average of A plus B minus their product. If only one part arrives, the system can keep the contactors closed and name the generator whose share is missing as a fault candidate, though the real cause may sit outside it. The aim is to avoid needless shutdowns caused by a failing monitoring part. Under such logic a performance code may be logged while the vehicle still drives. No maker documents U353A.

Likely causes

One of the loop M signal sources weak or failed
Loose contact in a loop M connector distorting the signal
Detection circuit for loop M faulty

Symptoms

  • Warning lamp while the vehicle keeps driving
  • Occasional loss of high voltage if the second channel also degrades

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€100–2,000
Time1–5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

hvil loop m

Related codes

U3539U353BU353CU3536P0A0B

References: patents.google.com, law.cornell.edu.