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Home / DTC / U3526 — High Voltage System Interlock Circuit G Performance

U3526 — High Voltage System Interlock Circuit G Performance

Detailed page for trouble code U3526.

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Code

U3526

Generic U — Network/User

High Voltage System Interlock Circuit G Performance

Brand: Generic
Type: U — Network/User
Views: UK: 16 EN: 29 RU: 16
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Page language: EN

Causes

  • Open or short in HV interlock circuit wiring (broken wire, chafing, corrosion)
  • Corroded, loose, bent or pushed-out connector pins at interlock switch or control module
  • Failed interlock switch / sensor (mechanical or electrical failure)
  • Faulty or contaminated HV interlock mating surfaces (poor contact)
  • Poor battery/main ground or connector at the control module
  • Short or leakage to chassis or to high-voltage conductors

Symptoms

  • High-voltage system disabled or unable to engage (EV drive/charge inhibited)
  • Ready or EV system warning lamp / HV system warning on the dash
  • Reduced propulsion power or limp-home mode
  • Vehicle may not start or will not shift into drive (depending on architecture)
  • Related modules may log communication faults or limp behavior
  • Intermittent faults that come and go with vibration or temperature changes

What to check

  • Read and record U3526 plus any additional stored or pending codes and freeze frame data
  • Check vehicle 12V battery state — low supply can cause false readings
  • Visually inspect HV interlock switch, harness routing, connectors and shielding for damage, corrosion or moisture
  • Check for bent/damaged pins and proper terminal seating at both ends of the interlock harness
  • Perform continuity and resistance checks of the interlock circuit with ignition off (compare to service spec)
  • Perform insulation/leakage check between interlock wiring and chassis/high-voltage conductors when required and safe

Signal parameters

  • Expected circuit continuity when interlock engaged: low resistance (typically
  • Expected open-circuit resistance when interlock disengaged: very high / infinite (open)
  • Expected digital signal voltage levels (if present): either contact closure to ground or a 0–5 V switched signal; verify against model wiring diagram
  • No short to battery positive or to chassis ground (insulation resistance high, e.g., >100 kΩ depending on spec)
  • Signal should be steady (no rapid fluctuations) while the interlock is in a fixed state

Diagnostic algorithm

  1. Retrieve and document all DTCs and freeze frame data. Note conditions when code set (temperature, voltage, vehicle state).
  2. Verify 12V battery condition and charge level. Clear codes and attempt to re-create the fault with a fully charged battery.
  3. Perform a thorough visual inspection of Interlock G harness, connectors, and the interlock device for contamination, damage, or loose pins.
  4. With ignition off and HV system made safe per manufacturer procedures, disconnect the interlock connector and measure continuity/resistance across the switch terminals. Compare to spec.
  5. Check for shorts: measure resistance from the interlock signal to battery positive and to chassis ground (should not be a short).
  6. Reconnect and power up. Monitor the interlock signal with a scan tool or multimeter while actuating the interlock (or moving harness) to look for intermittent changes. Perform a wiggle test.
  7. Inspect and test related fuses, relays, and ground connections. Repair or replace any damaged wiring or connectors found.
  8. If wiring and switch test good, check for relevant software updates or known module issues. If available, perform module reprogramming per service instructions.
  9. If fault persists after repairs and software checks, consider substituting the interlock sensor/switch or the controlling module following manufacturer diagnostic procedures.
  10. After repair, clear codes and perform a full system test/road test to confirm repair. Re-scan for stored or pending codes.

Likely causes

  • Damaged connector or wiring at the HV interlock switch
  • Interlock switch contact failure (stuck or intermittent)
  • Corrosion or water intrusion at connector causing intermittent contact
  • Open continuity in the interlock harness due to chafe or pinched cable
  • Module reporting error after a transient condition (vehicle battery low or startup surge)

Fault status

⚠️ Status
High Voltage System Interlock Circuit G Performance — signal out of expected range or intermittent. HV system may be disabled or limited for safety. Further inspection of interlock wiring, connectors, and switch required.
🔴 Repair difficulty: Hard
⏱️ Diagnostic time: 1.5-3.0 hours

Similar codes

U3525 U3527 U0100 U0121 U0131
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