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Home / DTC / U353E — High Voltage System Interlock Circuit N Performance

U353E — High Voltage System Interlock Circuit N Performance

Detailed page for trouble code U353E.

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Code

U353E

Generic U — Network/User

High Voltage System Interlock Circuit N Performance

Brand: Generic
Type: U — Network/User
Views: UK: 11 EN: 18 RU: 15
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Page language: EN

Causes

  • Damaged or corroded HV interlock (HVIL) connector or terminals
  • Broken, pinched, or chafed HVIL wiring harness
  • Poor mating of high-voltage connectors or seals allowing moisture intrusion
  • Faulty HVIL sensor or junction block (module)
  • Intermittent connector contact (loose retention)
  • Short to chassis ground or to other conductor in the HVIL circuit

Symptoms

  • HV system disablement or inhibited ability to start EV/HEV drive
  • Reduced available drive power or limp-home mode
  • HV system warning indicator or general malfunction lamp illuminated
  • Charging disabled (EVs) or inability to enter ready/drive state
  • Possible intermittent faults that come and go depending on temperature/vibration

What to check

  • Read and record freeze frame and all stored HVIL and related codes from all modules
  • Confirm vehicle safety procedure for high-voltage work before any physical checks
  • Visually inspect all HV connectors in the interlock loop for corrosion, deformation, loose/crossed pins, or broken latches
  • Perform wiggle test on HVIL wiring with scan tool data monitoring to observe intermittent changes
  • Measure continuity/resistance of the HVIL loop with HV system disabled and isolated (follow OEM HV safety)
  • Check for unintended continuity between HVIL conductors and chassis ground

Signal parameters

  • Closed/normal HVIL loop: very low resistance (typically near 0–2 ohms) or continuity present
  • Open HVIL loop: very high resistance or infinite (open circuit) when connectors are separated
  • Some systems present a reference voltage (often 5 V) or low-voltage pulsed signal to the HVIL circuit—expected steady voltage when intact; erratic or intermittent pulses indicate a fault
  • No measurable short to chassis ground (infinite/very high resistance between HVIL conductor and vehicle ground)

Diagnostic algorithm

  1. Follow OEM high-voltage safety procedure; isolate and de-energize HV system before access.
  2. Scan all modules and record DTCs and live data. Note related/secondary codes (communication or other HVIL codes).
  3. Visually inspect HVIL harness, connectors, and junctions for damage, contamination, or loose latches. Repair visible damage.
  4. With HV safely de-energized, disconnect at logical locations and measure continuity/resistance across the HVIL “N” loop; compare to expected closed/open values.
  5. Perform a wiggle/test with the scan tool monitoring HVIL status: gently move connectors, harness, and components to reproduce the fault.
  6. Check resistance between HVIL conductor and chassis ground to confirm no unintended short.
  7. If intermittent persists and wiring/connector checks are good, swap or bench-test the suspected HVIL sensor/junction block or replace the connector assembly per OEM guidance.
  8. After repairs, clear codes, re-enable HV system per safety procedure, and perform a functional test and road/driving/charging cycle to confirm the fault does not return.
  9. If faults remain and wiring and components are good, suspect control module input or software—verify software level and consult OEM for reprogramming or module replacement guidance.

Likely causes

  • Corroded or contaminated HV connector at the component or junction block
  • Wiring abrasion through insulation at a harness grommet or bend
  • Connector not fully seated after service or maintenance
  • Water ingress at connector leading to high resistance or intermittent contact

Fault status

⚠️ Status
High Voltage System Interlock Circuit N reports performance outside expected range (open, high resistance, short, or intermittent), causing the HV system to be disabled or enter a protective mode.
🔴 Repair difficulty: Hard
⏱️ Diagnostic time: 1.5-3.0 hours

Similar codes

U353F U353C U353D U0100 P1A7A
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