Network, generic (extended)

U3548 High Voltage System Interlock Circuit P High

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

U3548 is the high-side code of loop P. When each unit adds a known share of loop resistance, a single suspect can be isolated by substitution. Tesla's Model S HVIL guide has technicians, after consulting a field engineer, place a 60-ohm resistor across the drive inverter's interlock pins at connector X250 and also bridge its CAN lines; if the contactors then close, the inverter's internal section is to blame. Such a stand-in serves only as a short test by trained staff and must be removed afterwards. No maker documents U3548. A raised reading calls for measuring the share of each component on loop P.

Likely causes

Internal interlock section of an HV component too resistive
Loop P wire shorted to a 12 V feed
Loose or poorly crimped interlock terminal in loop P

Symptoms

  • Contactors stay open, no ready mode
  • High-voltage system warning
  • Charging blocked

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 phvil wiring

Related codes

U3545U3546U3547U3544P0A0D

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