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Home / DTC / U3545 — High Voltage System Interlock Circuit P

U3545 — High Voltage System Interlock Circuit P

Detailed page for trouble code U3545.

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U3545

Generic U — Network/User

High Voltage System Interlock Circuit P

Brand: Generic
Type: U — Network/User
Views: UK: 14 EN: 20 RU: 13
AI status
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Page language: EN

Causes

  • Open or shorted interlock wiring harness
  • Corroded, loose or damaged interlock connector
  • Faulty interlock switch or physical locking mechanism (charge port, service plug, HV connector interlock)
  • High resistance in circuit due to corrosion or partial break
  • Blown fuse, relay, or protective device in the interlock circuit
  • Faulty HV control module or body control module input

Symptoms

  • HV system disabled or inhibited (no high-voltage power enabled)
  • Vehicle won’t enter EV/ready state or won’t start
  • Charging disabled or charge port lock/unlock faults
  • HV warning indicator or fault lamp illuminated
  • Reduced propulsion or limp mode if hybrid system refuses to enable HV components
  • Diagnostic trouble codes related to HV interlock or HV system enablement present

What to check

  • Follow manufacturer HV safety procedures and isolate/de-energize HV system before touching high-voltage components
  • Visual inspection of interlock wiring harness and connectors for damage, corrosion, chafing or water ingress
  • Inspect interlock switches (charge port latch, service disconnect, HV connector interlock) for correct mechanical operation
  • Check inline fuses and relays related to interlock circuits and replace if blown/faulty
  • Verify connectors are fully seated and locking tabs engaged
  • Scan HV control module and related modules for additional codes and freeze frame data

Signal parameters

  • Typical circuit type: low-voltage interlock sense (vehicle-dependent; often a switched 0–12 V or a resistance-sensed loop)
  • Closed/interlock-asserted: continuity across interlock loop; expected DC resistance typically very low (< 2–5 Ω) or a specific manufacturer resistor value — consult service data
  • Open/interlock-not-asserted: open-circuit or very high resistance (>> 10 kΩ) or voltage pulled to supply (e.g., ~12 V) depending on design
  • Module input voltage when HV system enabled: nominal referenced supply (e.g., 5 V or 12 V logic levels) — verify exact thresholds from vehicle electrical manual

Diagnostic algorithm

  1. Read and record all stored codes and freeze-frame data from HV control module and related modules.
  2. Ensure HV system is made safe: de-energize HV battery per manufacturer procedure and use required PPE. Do not probe live high-voltage conductors without training/equipment.
  3. Perform visual inspection of interlock wiring, connectors, and switches (charge port, service plug, HV connector). Repair or replace damaged components.
  4. With HV system de-energized, measure continuity/resistance of the interlock loop between the HV control module input and interlock switch(s). Compare to manufacturer specification; look for open circuits or excessive resistance.
  5. Inspect and test any inline fuses, fusible links, or relays in the interlock circuit. Replace as necessary.
  6. Reconnect and, if safe per procedure, perform voltage/signal checks at the module input while cycling interlock switches (or with a jumper where allowed by service manual) to confirm correct logic levels. Do not bypass safety devices except where allowed by documentation for testing.

Likely causes

  • Open or damaged interlock wiring between HV connector and HV control module
  • Corroded connector or pin causing intermittent/high resistance
  • Failed interlock switch on charge port or service disconnect
  • Blown inline fuse or failed relay in interlock supply/return
  • HV control module input driver failure

Fault status

⚠️ Status
HV System Interlock Circuit P fault detected — interlock circuit open/short/high resistance or unexpected signal; high-voltage system may be disabled until fault is resolved.
🔴 Repair difficulty: Hard
⏱️ Diagnostic time: 1-3 hours

Similar codes

U3544 U3546 U0100 U0073 P0A7F
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