Network, generic (extended)

U3544 High Voltage System Interlock Circuit O High

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

U3544 sets when loop O delivers too high a value. A plug can hold its specified torque and still sit crooked. FCA's STAR case S2108000121 (Rev. B, 2026) for Wrangler and Grand Cherokee 4xe models describes P0A0A after HV repairs although the connector bolts reached 9 Nm: the plug had gone on at an angle, the C3 connector of the power inverter module in particular. Three windows around its shield must show bare aluminium housing with no gap; spread interlock terminals mean replacing the HV component. In a current-fed loop such poor contact appears as a higher value. No maker documents U3544. Seat each plug squarely before tightening.

Likely causes

HV plug on loop O torqued down while tilted
Interlock terminals spread by a crooked fitting
Loop O wire shorted to a 12 V feed
Connector bolt thread stripped so the plug cannot be clamped

Symptoms

  • Check engine light and hybrid system message right after an HV repair
  • No ready mode

Repair estimate

DifficultyHardWorkshop job
Parts and labour€60–3,000
Time0.5–5 h

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

Parts involved

hvil loop ohvil wiring

Related codes

U3541U3542U3543U3540P0A0D

References: static.nhtsa.gov, law.cornell.edu.