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Home / DTC / U352B — High Voltage System Interlock Circuit H Low

U352B — High Voltage System Interlock Circuit H Low

Detailed page for trouble code U352B.

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Code

U352B

Generic U — Network/User

High Voltage System Interlock Circuit H Low

Brand: Generic
Type: U — Network/User
Views: UK: 22 EN: 34 RU: 26
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Page language: EN

Causes

  • Short to ground on the interlock circuit wiring
  • Faulty or stuck interlock switch (service plug, charge inlet, HV connector interlock)
  • Corroded, loose, or damaged interlock connector pins
  • Faulty HV System Control Module or body controller input circuit
  • Water intrusion or contamination at interlock connectors
  • Incorrectly installed service disconnect or interlock hardware

Symptoms

  • HV system disabled or inhibited (vehicle will not enable high-voltage systems)
  • HV warning lamp or master warning illuminated
  • No EV drive or reduced power mode
  • Inability to charge HV battery (charge inhibited)
  • Related interlock or service plug fault messages displayed

What to check

  • Follow all manufacturer high-voltage safety procedures before any inspection or measurement
  • Scan for stored and pending DTCs and freeze frame data; record data
  • Visually inspect interlock wiring harnesses, connectors, and service plug/charge inlet for damage, contamination, or corrosion
  • Check connector security and pin condition at interlock devices and control modules
  • Measure voltage at the interlock circuit pin with respect to vehicle ground and with interlocks in known states (service plug inserted/removed, charge inlet closed/open)
  • Perform continuity and resistance checks from module input to interlock switch and to ground

Signal parameters

  • Expected logic levels vary by vehicle; commonly interlock inputs use a reference (e.g., ~5 V) pulled to ground when interlock is activated or a pull-up to module voltage when open
  • Fault condition here reported as 'low' — measured near 0 V (ground) at the module input when it should be high or open
  • Open circuit typically shows high impedance/voltage per module pull-up; short-to-ground shows ~0 V
  • Typical continuity: closed interlock switch < 5 ohms; open switch shows infinite or very high resistance (manufacturer specs vary)

Diagnostic algorithm

  1. Read and record U352B and any related DTCs and freeze frame data with scan tool.
  2. Ensure the vehicle is made safe for HV service (isolate HV battery, remove service disconnect where required) before touching HV components or connectors.
  3. Inspect physically all interlock-related connectors (service plug, charge port, HV junctions) for damage, corrosion, loose pins, or water intrusion.
  4. With vehicle powered as required by manufacturer and safety procedures followed, back-probe the interlock circuit at the control module and at the interlock switch. Verify voltage and state change when operating the interlock (insert/remove service plug, open/close charge inlet).
  5. If the circuit reads low at the module but not at the interlock device, test continuity between the module and the device to locate a short to ground. Repair any chafing or pin-contact faults.
  6. If the circuit reads low at the device, test the switch itself. Replace the interlock switch or service plug assembly if it shorts to ground when it should be open.
  7. If wiring and interlock switch check good, suspect module input failure. Confirm with module diagnostics and, if possible, swap or bench-test module input per manufacturer procedures before module replacement.
  8. After repairs, clear codes, perform functional tests of HV enable/disable and charging, and confirm no recurrence of U352B.

Likely causes

  • Wiring harness chafed and shorted to chassis ground near HV junctions
  • Interlock switch internally shorted or mechanically stuck closed
  • Connector terminal corrosion causing low resistance to ground
  • Control module input transistor or circuit failure
  • Aftermarket work or collision damage disturbed interlock wiring

Fault status

⚠️ Status
High Voltage System Interlock Circuit H reported low (shorted/grounded) input — HV system disabled until fault is corrected.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-3.0 hours

Similar codes

U352A U352C U0100 U0121
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