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Home / DTC / U351E — High Voltage System Interlock Circuit E Performance

U351E — High Voltage System Interlock Circuit E Performance

Detailed page for trouble code U351E.

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U351E

Generic U — Network/User

High Voltage System Interlock Circuit E Performance

Brand: Generic
Type: U — Network/User
Views: UK: 20 EN: 31 RU: 19
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Page language: EN

Causes

  • Damaged or corroded connectors in the high-voltage interlock loop
  • Open, shorted or high-resistance wiring in the interlock circuit
  • Faulty interlock switch, sensor, or loop monitoring module
  • Poor ground or supply to the monitoring circuit
  • Intermittent connector contact due to vibration or improper seating
  • Software/firmware bug or communication error in the managing ECU (less common)

Symptoms

  • HV system disabled or unable to enable (vehicle won’t enter READY state)
  • HV-related warning lights or message (e.g., HV system fault, service required)
  • Reduced drive power or limp mode
  • Intermittent loss of HV enablement or random shut-down of HV functions
  • DTC U351E stored, possibly with related codes

What to check

  • Obtain and record freeze-frame and related codes using a capable scan tool; check for other HV or communication codes
  • Visually inspect interlock circuit routing: connectors, service disconnects, charge inlet, and battery access plugs for corrosion, damage or looseness
  • Confirm correct torquing/seating of removable HV interlocks (service plugs) and inspect for intrusion of debris
  • Inspect fuses and relays related to the interlock monitor/supply circuit
  • Using appropriate safety procedures for HV systems, check continuity and resistance of the interlock loop at serviceable points (with HV isolated/)
  • Check connector pins for damage, corrosion or bent terminals and verify secure locking

Signal parameters

  • Interlock circuit is typically a closed/open loop monitored by the module — expected: closed (low resistance) when assembled, open (high/OL) when service plug removed
  • Monitoring circuit will report discrete state (Open/Closed) or a DC voltage near 0 V or battery-supply voltage depending on design — compare to factory wiring diagram and live-data values
  • Continuity: low ohms across closed interlock contacts; infinite/OL when open. Excessive resistance (hundreds of ohms) indicates a problem
  • CAN/UH communication: interlock status bits should update when physical interlock is changed; absence of updates indicates wiring/module/communication issue

Diagnostic algorithm

  1. Safety first: follow vehicle manufacturer HV isolation and PPE procedures before touching any high-voltage components.
  2. Connect a factory-level or equivalent scan tool; read and record U351E and any related codes and freeze-frame data.
  3. Inspect visible interlock components and connectors (service plug, charge inlet interlock, battery disconnects). Repair or reseat any corrosion/loose connectors.
  4. Clear the code and attempt to reproduce while monitoring live-data interlock status. Note whether the DTC returns and under what conditions.
  5. With HV isolated as required, perform continuity and resistance checks of the interlock loop at serviceable points. Compare measured values to the expected (closed ≈ low ohms; open ≈ OL).
  6. If continuity is abnormal, isolate the section with the fault by disconnecting segments and repeating checks to locate the open/high-resistance area.
  7. Inspect and test power and ground feeds to the interlock monitoring module, including related fuses and relays.
  8. If wiring and connectors check good, swap or bench-test the interlock switch/module if a known-good component is available or follow manufacturer guidance for module testing.
  9. If fault is intermittent, perform vibration/wiggle tests on harnesses and connectors while monitoring live data to find intermittent contact.
  10. After repair, clear codes, perform full system enable sequence, and verify the interlock reports correct states and that the HV system enables normally.
  11. If unable to isolate, consult OEM wiring diagrams, interlock loop schematics, and technical service bulletins; escalate to manufacturer-level diagnostics as required.

Likely causes

  • Corroded/loose interlock connector at a service plug, charge inlet, or battery disconnect
  • Broken conductor or chafed wiring in harness where it flexes
  • High-resistance connection at interlock switch or contacting surfaces
  • Failed interlock switch or loop monitor module
  • Blown fuse or tripped relay supplying the interlock monitor

Fault status

⚠️ Status
High-voltage interlock circuit E is outside expected performance (open, short, high resistance, or failing to report state). The control module may disable the HV system until the circuit is repaired or validated.
🔴 Repair difficulty: Hard
⏱️ Diagnostic time: 1.5-4.0 hours

Similar codes

U351F U3515 U3500 U0100 U1000
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