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Home / DTC / U3519 — High Voltage System Interlock Circuit D

U3519 — High Voltage System Interlock Circuit D

Detailed page for trouble code U3519.

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Code

U3519

Generic U — Network/User

High Voltage System Interlock Circuit D

Brand: Generic
Type: U — Network/User
Views: UK: 16 EN: 21 RU: 18
AI status
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Page language: EN

Causes

  • Open circuit in interlock D wiring (broken conductor, disconnected pin)
  • Short to battery positive or chassis ground on interlock D wiring
  • Corroded, bent, or poorly seated connector at interlock switch, junction box, battery pack or HV service disconnect
  • Faulty interlock switch, interlock harness, or HV disconnect (service plug)
  • HV system control module or monitoring circuit internal failure
  • Moisture ingress or contamination in connector or junction box

Symptoms

  • HV system disabled or prevents HV contactors from closing
  • Vehicle may not enter READY state or may go into limp/reduced-power mode
  • HV charge or drive functions unavailable
  • DTC stored in HV system controller; corresponding warnings on dash or touch screen
  • Charging disabled (for plug-in vehicles)

What to check

  • Read and record freeze frame and related DTCs with a capable scan tool
  • Confirm vehicle is placed into safe state and follow manufacturer HV safety procedure before any physical inspection
  • Visual inspection of interlock D wiring, connectors, and HV service disconnect for damage, corrosion, or loose pins
  • Verify service plug / HV interlock is fully seated and lock/retainer engaged
  • Check for water/moisture in junction boxes and connectors
  • Inspect for signs of repair or aftermarket splices in interlock wiring

Signal parameters

  • Interlock circuits are low-voltage status/switch circuits (typically 0–5 V logic or simple continuity to ground) — expected: continuity (low resistance) when interlock is engaged/closed
  • Open-circuit (very high resistance or OL) when interlock is physically removed/unseated
  • Some systems report interlock status as a discrete CAN/BUS message — expected logical state = “closed” (OK) when service plug seated
  • No high-voltage present on the interlock conductor; measure only low-voltage signals after isolating HV per safety procedure

Diagnostic algorithm

  1. Obtain full scan data and note related codes and freeze-frame data.
  2. Place vehicle in a safe, de-energized condition following HV safety procedures (isolate HV battery, remove service plug if required by procedure).
  3. Perform a careful visual inspection of the HV interlock D harness, connectors, and service disconnect for damage, corrosion, water ingress, or loose pins.
  4. With the system made safe per manufacturer procedure, perform continuity/resistance check of the interlock D conductor between the service disconnect/interlock switch and the HV control module. Compare to expected values in repair manual.
  5. If continuity is open, inspect and repair/replace damaged wiring or connectors. If short to ground or battery positive is found, isolate the short by disconnecting intermediate connectors and retest segments to locate fault.
  6. With vehicle in the powered/diagnostic state (only when allowed and following safety steps), measure interlock signal voltage relative to chassis ground and compare against expected logic levels; do not measure live HV conductors.
  7. Wiggle harness/connectors while monitoring interlock status with scan tool to detect intermittent faults.
  8. Check and test the interlock switch or service plug assembly; replace if mechanical failure or internal corrosion is found.
  9. If wiring and switch check good, suspect HV system control module or monitor. Verify reference voltages and grounds at the module and consult wiring diagrams; replace module only after confirming harness and peripheral components.
  10. After repair, clear codes, perform functional test/relearn procedures, and perform road/operational test to ensure code does not return.

Likely causes

  • Disconnected or corroded connector at the service disconnect or HV junction box
  • Open/short in the interlock harness near a serviceable connector
  • Service plug or interlock switch not fully seated or damaged

Fault status

⚠️ Status
High Voltage System Interlock Circuit D — open/short or communication fault detected. HV system may be disabled.
🔴 Repair difficulty: Hard
⏱️ Diagnostic time: 2-5 hours

Similar codes

U3500 U3510 U3518 U3520
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