Network, generic (extended)

U3533 High Voltage System Interlock Circuit K Low

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

U3533 says loop K reads too low. Apart from an open plug, part of the loop current may be escaping somewhere. Tesla's HVIL tech note for the Model S describes two such cases: a drive inverter whose control board leaked some of the nominal 20 mA loop current to ground, and a loop wire squeezed against ground close to a seat belt pretensioner. The fault therefore need not sit in a connector at all; a component on the loop or a wire trapped by seat or trim parts can cause it. When every plug of loop K is latched and the value stays low, measure the loop current at each component and inspect wiring near seat mounts. No maker documents U3533; the contactors remain open.

Likely causes

Loop K wire squeezed against ground by seat, trim or mounting parts
Plug within loop K not connected
High-voltage component on loop K leaking loop current to ground internally

Symptoms

  • Vehicle does not reach ready mode
  • Fault may follow work on seats or interior trim
  • Warning to have the high-voltage system checked

Repair estimate

DifficultyHardWorkshop job
Parts and labour€80–2,000
Time0.5–5 h

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

Parts involved

hvil loop khvil wiring

Related codes

U3531U3532U3534U352FP0A0C

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