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Home / DTC / U351F — High Voltage System Interlock Circuit E Low

U351F — High Voltage System Interlock Circuit E Low

Detailed page for trouble code U351F.

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Code

U351F

Generic U — Network/User

High Voltage System Interlock Circuit E Low

Brand: Generic
Type: U — Network/User
Views: UK: 19 EN: 27 RU: 26
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Page language: EN

Causes

  • Open or shorted wiring in HVIL Circuit E (open to ground or short to battery negative)
  • Corroded, loose, or damaged connector at an HV interlock switch or harness
  • Faulty interlock switch (e.g., service disconnect, charge port latch, battery service plug sensor)
  • Moisture or contamination in interlock connectors or harness
  • Blown or open fuse/fusible link supplying the interlock circuit sensing/reference
  • Faulty control module or incorrect module reference/input for the interlock circuit

Symptoms

  • HV system disabled or vehicle will not enter Ready/Drive state
  • HVIL or Master Warning indicator and related dashboard messages
  • Charging may be disabled or show an error
  • Reduced propulsion or limp mode depending on vehicle design
  • DTCs for related HV circuits or loss of communication with HV modules

What to check

  • Observe and record freeze-frame and related DTCs with a scan tool
  • Visually inspect HV interlock connectors, service disconnect/plug, charge inlet, and routing for damage, corrosion, or moisture
  • Verify all HV service plugs, interlock switches and latches are fully seated and engaged
  • Check for other HV or communication DTCs that may be related
  • Use a DVOM/scan tool to read live HVIL status values (voltage/resistance) if available
  • Perform a wiggle/short test while monitoring live data only after following HV safety procedures

Signal parameters

  • Expected: HVIL closed/healthy state typically reports near supply/reference voltage (vehicle 12 V domain) or a defined non-zero analog voltage — consult vehicle-specific data
  • Fault/low: voltage on Circuit E measured at the sensing input typically low or near 0 V when open/shorted to ground
  • Continuity: a healthy closed interlock loop normally shows continuity (low resistance) across the loop; an open loop shows very high or infinite resistance
  • Note: exact voltages, resistance thresholds and logic levels are manufacturer-specific; consult the vehicle wiring diagram and service manual for numeric limits

Diagnostic algorithm

  1. WARNING: Follow all high-voltage safety procedures, wear PPE, and isolate high-voltage system per manufacturer instructions before performing any hands-on tests.
  2. Retrieve and record all HV-related DTCs and freeze-frame data with a capable scan tool. Note module reporting U351F and any other codes.
  3. Visually inspect connectors and harnesses for Circuit E components: battery service disconnect, charge inlet interlock, DC/DC isolation switch, and any removable HV modules. Look for loosened latches, corrosion or water.
  4. Verify service plug/service disconnect is fully inserted and locked. Re-seat connectors where safe to do so (with HV isolated).
  5. With high-voltage system isolated and safe to work on, measure continuity/resistance of the interlock loop for Circuit E between the sensing connector and each expected interlock device. Compare to spec if available.
  6. With power applied and using insulated test equipment and strict HV procedures, measure voltage at the interlock sense input while operating/engaging interlock devices (charge port latch, service plug) to see if the voltage changes as expected. Do not probe live HV conductors — probe only low-voltage interlock circuitry per service manual.
  7. Perform wiggle/connector-reseat checks while monitoring live data to find intermittent faults. Check for shorts to chassis ground on the Circuit E wiring.
  8. If wiring and connectors check good, swap or bench-test the suspect interlock switch/component if a known-good unit is available, or replace the connector/repair wiring as needed.
  9. After repair, clear codes, perform a full system power cycle, and verify the U351F does not return during functional checks (charging, HV enable) and a road/test procedure as recommended.
  10. If the code persists and wiring/interlocks test normal, consider module input/sensor circuit fault — refer to manufacturer module diagnostics or replace module only after exhaustive verification.

Likely causes

  • Disconnected or poorly-seated HV service plug or battery connector
  • Damaged/intermittent pin or terminal in HV interlock connector near the battery, charging inlet, or safety disconnect
  • Corrosion or water ingress at interlock switch (charge port, DC/DC disconnect, etc.)
  • Wire chafing causing intermittent short to chassis ground on Circuit E
  • Failed interlock sensor/switch on a removable HV component

Fault status

⚠️ Status
U351F — High Voltage System Interlock Circuit E: voltage below expected threshold (interlock open/short/poor connection). HV system may be disabled.
🔴 Repair difficulty: Hard
⏱️ Diagnostic time: 1-4 hours

Similar codes

U351E U3510 U0100 U0121 U3000
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