U352B

Code

Generic U — Network/User

High Voltage System Interlock Circuit H Low

Brand: Generic

Type: U — Network/User

Views: UK: 27 EN: 40 RU: 29

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Page language: EN

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

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

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)

Read and record U352B and any related DTCs and freeze frame data with scan tool.
Ensure the vehicle is made safe for HV service (isolate HV battery, remove service disconnect where required) before touching HV components or connectors.
Inspect physically all interlock-related connectors (service plug, charge port, HV junctions) for damage, corrosion, loose pins, or water intrusion.
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).
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.
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.
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.
After repairs, clear codes, perform functional tests of HV enable/disable and charging, and confirm no recurrence of U352B.