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Home / DTC / U3514 — High Voltage System Interlock Circuit B High

U3514 — High Voltage System Interlock Circuit B High

Detailed page for trouble code U3514.

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U3514

Generic U — Network/User

High Voltage System Interlock Circuit B High

Brand: Generic
Type: U — Network/User
Views: UK: 12 EN: 25 RU: 15
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Page language: EN

Causes

  • Open or broken wiring in interlock circuit B
  • Connector corrosion, poor contact, or water intrusion at interlock/charge inlet/service plug
  • Faulty interlock switch or sensor (service disconnect, charge port interlock, HV access connector)
  • Short to battery positive or other supply producing a high voltage on the circuit
  • Faulty body/BCM or hybrid control module input stage
  • Aftermarket modifications or incorrect reassembly after service

Symptoms

  • HV system disabled or prevented from enabling (no EV drive / no hybrid assist)
  • Traction/EV system warning lights or master warning on dash
  • Reduced power, limp-home mode, or inability to start the vehicle
  • Charging disabled or charge port fault (for plug-in vehicles)
  • DTC U3514 stored in vehicle control module(s)

What to check

  • Read and record DTC(s) and freeze frame data from all related control modules
  • Visual inspection of interlock circuit B wiring, connectors, charge inlet, and service disconnect for damage or corrosion
  • Inspect for signs of water ingress, pin damage, or loose terminals at the interlock components
  • Check the position and condition of any removable high-voltage interlock plugs/connectors
  • Measure voltage at the interlock circuit pin at the module and at the interlock device with a DMM
  • Perform continuity/resistance checks of the interlock loop with vehicle powered down and HV system safely isolated

Signal parameters

  • Expected closed/normal interlock: low voltage or near 0 V (circuit pulled to ground) — exact threshold is manufacturer specific
  • Fault/High condition: voltage close to battery/ignition supply (e.g., ~12 V) or a voltage above the module's high threshold
  • Open/high-impedance may also read as a floating voltage (varies by meter and vehicle)
  • Typical continuity: near 0 ohms around the loop when interlock is closed; infinite or very high resistance if open/broken

Diagnostic algorithm

  1. Record all stored codes and freeze frame data from relevant modules (HV controller, BMS, BCM, charger).
  2. Visually inspect interlock B wiring, connectors, charge inlet, and service disconnect for damage/corrosion; repair visible damage.
  3. With vehicle in a safe, de-energized state per manufacturer procedures, perform continuity/resistance check of the interlock loop from module pin to interlock device and around the harness.
  4. Re-energize vehicle (follow HV safety procedures) and measure voltage at the interlock input pin and at the interlock device while cycling the service disconnect/charge plug; record voltages.
  5. Wiggle test wiring and connectors while monitoring live data/voltage to identify intermittent faults.
  6. If voltage indicates a short to supply, isolate sections of harness to find short (disconnect connectors sequentially); repair short to supply.
  7. If open/broken wiring is found, repair or replace wiring/harness and damaged connectors; clean and secure all terminals.
  8. If wiring and connectors are good but voltage remains incorrect, swap or bench-test the interlock switch/device if serviceable; replace if faulty.
  9. If the interlock device and wiring test good, consider module input failure — verify with wiring diagrams and perform module replacement only after confirming upstream causes.
  10. Clear DTCs and perform a functional test: cycle service disconnect/charge connector and verify HV system enables normally and codes do not return.

Likely causes

  • Corroded/loose connector at the HV interlock or charge inlet
  • Broken conductor in the interlock loop (pinched or cut harness)
  • Faulty interlock switch (stuck open or internally shorted)
  • Short to battery positive on the interlock return wiring
  • Failed module input (less common)

Fault status

⚠️ Status
High Voltage System Interlock Circuit B voltage HIGH — interlock loop open or short to supply. HV enable may be inhibited.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

Similar codes

U3510 U3511 U3512 U3513 U3515 U0140
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