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Home / DTC / U3522 — High Voltage System Interlock Circuit F Performance

U3522 — High Voltage System Interlock Circuit F Performance

Detailed page for trouble code U3522.

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Code

U3522

Generic U — Network/User

High Voltage System Interlock Circuit F Performance

Brand: Generic
Type: U — Network/User
Views: UK: 19 EN: 21 RU: 19
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Page language: EN

Causes

  • Open or short in the interlock wiring harness for Interlock F
  • Corroded, loose or damaged HV interlock connector or pin
  • Faulty interlock switch, sensor, or jumper in the HV safety loop
  • Poor chassis or harness grounding affecting interlock signal
  • Faulty control module reading the interlock (HVECU, BMS, CCS) or CAN messaging
  • Water intrusion or contamination in HV connector area

Symptoms

  • HV system disablement or refusal to power on
  • Reduced driveability or limp mode with limited power available
  • HV warning light or dashboard message (e.g., HV system fault, service required)
  • Charging disabled or charging fault
  • Possible loss of associated CAN messages or related module warning lamps
  • Intermittent loss of HV functions (may be repeatable with vibration or temperature changes)

What to check

  • Observe safety first: de-energize high-voltage system and follow manufacturer HV safety procedures before touching HV components.
  • Use a scan tool to record freeze-frame data, monitor Interlock F status and related PID/live data.
  • Visually inspect interlock connectors, harness routing, ties, and strain reliefs for damage, corrosion, or contamination.
  • Check connector pins for corrosion, bent pins, or poor seating; reseat connectors and inspect contacts.
  • Measure continuity of the interlock loop with HV system de-energized (use appropriate meter and safety procedures).
  • Check for shorts to chassis by measuring insulation/isolation between interlock wiring and vehicle ground with HV system de-energized.

Signal parameters

  • Healthy interlock: closed safety loop / low resistance when components are correctly connected (continuity expected).
  • Fault condition: open circuit or high resistance in the interlock loop (loss of continuity).
  • No unintended voltage present on the interlock wiring when HV system is de-energized.
  • HV isolation: high resistance between HV circuit and chassis/ground (isolation should be very large — measured with proper test equipment).
  • Monitoring PIDs: Interlock status should match expected binary state (closed/open) reported by the HV control module.

Diagnostic algorithm

  1. Step 1 — Read codes and data: Connect a capable scan tool, record U3522 and any additional DTCs, capture freeze frame and live interlock status/PIDs.
  2. Step 2 — Safety and prep: Follow manufacturer HV lock-out procedures, remove service disconnects or contactors to de-energize the HV system before inspecting or measuring harness/connector continuity.
  3. Step 3 — Visual inspection: Inspect all connectors and harnesses associated with Interlock F (battery, inverter, junction box, charger inlet, service disconnect). Look for corrosion, water ingress, crushed wires, or damaged insulation.
  4. Step 4 — Connector service: De-pin and inspect connector contacts where safe and allowed. Clean and repair corroded contacts or replace connector assemblies as required.
  5. Step 5 — Continuity/isolation checks: With HV de-energized, measure continuity of the interlock loop end-to-end. Check for short to chassis/other circuits and verify insulation resistance between HV wiring and chassis ground with appropriate meter/tester.
  6. Step 6 — Module and CAN checks: Verify the HV controller/BMS and gateway modules are powered and communicating. Check related CAN bus voltages and message presence; look for communication timeouts that could explain false interlock faults.
  7. Step 7 — Recreate and test: If fault is intermittent, perform wiggle tests and functional tests of connectors/components while monitoring live data. Reconnect HV per procedure and run system self-tests or recharge attempts to confirm proper behavior.
  8. Step 8 — Repair and verify: Repair or replace faulty wiring, connectors, or interlock devices. After repairs, clear codes, re-run diagnostics, and perform final road or functional test to ensure the code does not return.

Likely causes

  • Disconnected or poorly seated interlock connector at HV battery, inverter, or junction box
  • Damaged insulation or physical harness damage near HVAC/charge/inverter junctions
  • Corroded pins causing high resistance in the interlock loop
  • Failed interlock device (mechanical or electronic) in the high-voltage safety chain
  • Software/configuration error or a module that intermittently fails to read the interlock state

Fault status

⚠️ Status
Interlock F performance fault detected — the high-voltage interlock circuit is outside expected parameters. HV system may disable or enter protective mode until repair.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.5 - 3.0 hours

Similar codes

U0100 U0140 U1000 U1116 U0401 U3100
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