Network, generic (extended)

U3543 High Voltage System Interlock Circuit O Low

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

With U3543, loop O has dropped under its minimum. Some plug designs let the fitter see the reason. An LG Electronics patent describes a high-voltage connector closed by turning a cover housing: the rotation moves an inner cap up or down so that the power terminals mate first and the shorter interlock tab last, while a scale on the plug housing shows how far the cover has turned. A cover left short of its end stop keeps the power pins engaged with the interlock still apart, exactly the picture of a low reading. No maker documents U3543. Turn each rotary plug on loop O fully home and check the scale.

Likely causes

Rotary HV plug on loop O not turned to its end position
Interlock tab or socket in a loop O plug bent or pushed back
Loop O wire shorted to ground

Symptoms

  • High voltage stays off after work on HV plugs
  • No ready mode
  • Charging not possible

Repair estimate

DifficultyHardWorkshop job
Parts and labour€60–1,200
Time0.5–4 h

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

Parts involved

hvil loop ohvil wiring

Related codes

U3541U3542U3544U353FP0A0C

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