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Home / DTC / U3525 — High Voltage System Interlock Circuit G

U3525 — High Voltage System Interlock Circuit G

Detailed page for trouble code U3525.

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Code

U3525

Generic U — Network/User

High Voltage System Interlock Circuit G

Brand: Generic
Type: U — Network/User
Views: UK: 16 EN: 21 RU: 19
AI status
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Page language: EN

Causes

  • Open or shorted interlock switch or sensor (Circuit G)
  • Damaged, corroded, or disconnected wiring/connectors in interlock harness
  • Poor connector pin contact or terminal corrosion
  • Faulty body control / HV safety / inverter control module input
  • Intermittent connection due to chafing, rubbing or broken conductor
  • Aftermarket modification or recent service left connector loose or misrouted

Symptoms

  • Malfunction Indicator Lamp (MIL) or HV warning lamp illuminated
  • Vehicle may refuse to enable high-voltage systems (no HV enable, no ready state)
  • Loss of EV/Hybrid drive or limited power mode
  • Stored U3525 (and possibly related) DTCs
  • Possible intermittent HV enable/disable events or inability to charge

What to check

  • Read and record all stored DTCs and freeze frame data with a capable scan tool
  • Check for additional related U- or P-codes in HV and communication modules
  • Visually inspect the wiring and connectors for Circuit G from the interlock switch/service plug to the controlling module
  • Inspect connector pins for corrosion, bent pins, or water ingress
  • Check fuses and HV interlock relays associated with the interlock circuit
  • Perform a wiggle test on the harness with monitor of live data or DTCs (do this with the vehicle safe and powered per procedure)

Signal parameters

  • Interlock continuity (closed): typically low resistance; expect
  • Interlock open: infinite/OL or >1 MΩ (open circuit)
  • Control module input voltage may be pulled to a reference (common systems use a pull-up to 5–12 V): expect either near 0 V (closed to ground) or near pull-up voltage when open — consult OEM data
  • No fluctuating voltages/noise on the circuit when static; intermittent or bouncing readings indicate a poor connection

Diagnostic algorithm

  1. Ensure personal and workshop HV safety equipment and procedures are in place before any HV work. De-energize HV system per manufacturer instructions if probing inside HV enclosures is required.
  2. Connect a dealer-level or capable scan tool. Read and note all codes and live data relating to HV interlocks and module inputs. Identify whether Circuit G is reported open, shorted, or intermittent.
  3. Visually inspect the interlock switch, service disconnect (inlet/service plug), and routing of Circuit G harness. Look for damage, corrosion, pin push-out, or water entry. Repair any obvious damage.
  4. With vehicle in a safe state per procedure, disconnect the harness connector at the interlock switch and measure continuity across the switch actuated states: verify closed resistance is low (
  5. Backprobe the control module connector (or use breakout adapter) and measure voltage at the Circuit G pin with ignition/ready state per OEM guidance. Compare to expected pull-up or ground levels from service data. If voltage is abnormal, suspect wiring or module input.
  6. If wiring shows open or short, perform pin-to-pin continuity and insulation checks between the interlock and module. Repair wiring (splice, replace harness section, or repair connector) as required and ensure correct routing and strain relief.
  7. If wiring and switch check OK, suspect module input driver fault. Test related grounds and power supplies to the module. If module power/ground are good and input still out of range, consider module replacement per OEM diagnostic flow.
  8. Clear codes, perform a controlled system re-enable and monitor live data. Confirm the HV system enables normally and no U3525 returns. Road test if necessary.
  9. Document repairs and retest. If intermittent faults remain, consider fixture testing or inspect for movement-induced shorts under load.

Likely causes

  • Connector at interlock switch (Circuit G) is loose or corroded
  • Wire harness chafed and shorting to chassis or another conductor
  • Interlock switch mechanically failed or not seated (service plug, charge port, cover)
  • Control module input driver or pull‑up/pull‑down circuit failed

Fault status

⚠️ Status
High Voltage System Interlock Circuit G — open/short/intermittent detected; HV enable prevented or faulted.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

Similar codes

U3524 U3526 U3500 U0001 U0100 U0121
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