U352A

Code

Generic U — Network/User

High Voltage System Interlock Circuit H Performance

Brand: Generic

Type: U — Network/User

Views: UK: 14 EN: 31 RU: 23

AI status

Completed

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Page language: EN

Causes

Open, short or high-resistance in HV interlock wiring or connectors
Corroded, bent or pushed-out terminal(s) at connector(s)
Faulty interlock switch, sensor or service plug detection switch
Poor or intermittent ground or reference at the control module
Contamination (water, corrosion) or mechanical damage to harness
HV battery service disconnect not fully seated or damaged

Symptoms

Malfunction Indicator Lamp (MIL) or HV system warning lamp illuminated
Reduced driveability or limp/limited-power mode (HV system disabled)
Inability to start or enable HV drive system
Loss of charging or HV contactor inhibited
Stored DTC U352A in control module(s)
Intermittent faults that clear and return under vibration or temperature change

What to check

Follow all manufacturer high-voltage safety procedures; remove service plug and/or isolate HV battery before inspecting or disconnecting HV components. Use appropriate PPE.
Retrieve freeze frame and live data with a capable scan tool; note HV interlock status bits and related DTCs
Visually inspect interlock harnesses, service plug, connectors and routing for damage, contamination or loosened fasteners
Inspect connector pins for corrosion, pushed-out terminals, melted insulation or burns
Verify connectors are fully seated and retention clips are intact
Check fuses, relays and contactors related to the interlock and HV enable circuits

Signal parameters

Interlock closed (normal): continuity near 0 Ω to a few ohms (typical < 5–10 Ω depending on vehicle)
Interlock open (disconnected): open circuit / OL (very high resistance)
Fault condition: intermittent continuity, elevated resistance (>> normal), or fluctuating signal state in live data
Control module expected logic/state: discrete 'closed' or 'open' flag in scan tool; no mid-level analog voltage should be present on a discrete interlock line
Voltage checks: signal line usually at battery or ground potential depending on design; refer to vehicle wiring diagram for exact reference voltages

Diagnostic algorithm

Verify the DTC and any related codes using a capable scan tool. Record freeze frame data and current HV interlock status bits.
Follow manufacturer HV safety procedures. Remove HV service plug or otherwise isolate the HV battery before touching HV harnesses or connectors.
Visually inspect the interlock harness, connectors, service plug and nearby components for damage, corrosion, dirt or water intrusion. Repair obvious problems.
With HV isolated, disconnect the interlock connector(s). Check connector pins for corrosion, bent or pushed-out terminals and clean or repair as required.
Measure continuity/resistance of the interlock circuit between the control module pin and the interlock switch/service plug contacts. Compare to specification (expect near 0 Ω when closed, open when disconnected).
If resistance is high or intermittent, trace the harness and repair damaged sections or replace connector(s).
Reconnect and, following safe procedures, re-enable the low-voltage diagnostic state to monitor live data while cycling the interlock (seat/remove service plug, operate service disconnect) to observe changes in the interlock status bit.
Inspect and test any related relays/contactors and ground points. Confirm proper operation of the interlock switch or sensor assembly.
If wiring and components test good, check for control module software updates and perform module reprogramming or replacement per manufacturer guidance.
Clear codes and perform a road/functional test to confirm the issue is resolved and the DTC does not return.

Likely causes

Damaged harness at a harness-to-chassis contact point or through chafing
Corroded pin or poor crimp at an interlock connector
Service disconnect (service plug) not fully engaged or worn contacts
Faulty interlock switch or sensor inside connector/plug
High resistance caused by partial short to chassis ground or contamination
PCM/BCM/EV system control module reporting erroneous data

Fault status

⚠️ Status

High Voltage System Interlock Circuit H — performance/implausible signal detected. HV interlock reported out of expected range; HV system may be disabled.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1-4 hours