U3525

Code

Generic U — Network/User

High Voltage System Interlock Circuit G

Brand: Generic

Type: U — Network/User

Views: UK: 25 EN: 33 RU: 31

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Open or shorted interlock switch or sensor (Circuit G)
Damaged, corroded, or disconnected wiring/connectors in interlock harness
Poor connector pin contact or terminal corrosion
Faulty body control / HV safety / inverter control module input
Intermittent connection due to chafing, rubbing or broken conductor
Aftermarket modification or recent service left connector loose or misrouted

Symptoms

Malfunction Indicator Lamp (MIL) or HV warning lamp illuminated
Vehicle may refuse to enable high-voltage systems (no HV enable, no ready state)
Loss of EV/Hybrid drive or limited power mode
Stored U3525 (and possibly related) DTCs
Possible intermittent HV enable/disable events or inability to charge

What to check

Read and record all stored DTCs and freeze frame data with a capable scan tool
Check for additional related U- or P-codes in HV and communication modules
Visually inspect the wiring and connectors for Circuit G from the interlock switch/service plug to the controlling module
Inspect connector pins for corrosion, bent pins, or water ingress
Check fuses and HV interlock relays associated with the interlock circuit
Perform a wiggle test on the harness with monitor of live data or DTCs (do this with the vehicle safe and powered per procedure)

Signal parameters

Interlock continuity (closed): typically low resistance; expect
Interlock open: infinite/OL or >1 MΩ (open circuit)
Control module input voltage may be pulled to a reference (common systems use a pull-up to 5–12 V): expect either near 0 V (closed to ground) or near pull-up voltage when open — consult OEM data
No fluctuating voltages/noise on the circuit when static; intermittent or bouncing readings indicate a poor connection

Diagnostic algorithm

Ensure personal and workshop HV safety equipment and procedures are in place before any HV work. De-energize HV system per manufacturer instructions if probing inside HV enclosures is required.
Connect a dealer-level or capable scan tool. Read and note all codes and live data relating to HV interlocks and module inputs. Identify whether Circuit G is reported open, shorted, or intermittent.
Visually inspect the interlock switch, service disconnect (inlet/service plug), and routing of Circuit G harness. Look for damage, corrosion, pin push-out, or water entry. Repair any obvious damage.
With vehicle in a safe state per procedure, disconnect the harness connector at the interlock switch and measure continuity across the switch actuated states: verify closed resistance is low (
Backprobe the control module connector (or use breakout adapter) and measure voltage at the Circuit G pin with ignition/ready state per OEM guidance. Compare to expected pull-up or ground levels from service data. If voltage is abnormal, suspect wiring or module input.
If wiring shows open or short, perform pin-to-pin continuity and insulation checks between the interlock and module. Repair wiring (splice, replace harness section, or repair connector) as required and ensure correct routing and strain relief.
If wiring and switch check OK, suspect module input driver fault. Test related grounds and power supplies to the module. If module power/ground are good and input still out of range, consider module replacement per OEM diagnostic flow.
Clear codes, perform a controlled system re-enable and monitor live data. Confirm the HV system enables normally and no U3525 returns. Road test if necessary.
Document repairs and retest. If intermittent faults remain, consider fixture testing or inspect for movement-induced shorts under load.

Likely causes

Connector at interlock switch (Circuit G) is loose or corroded
Wire harness chafed and shorting to chassis or another conductor
Interlock switch mechanically failed or not seated (service plug, charge port, cover)
Control module input driver or pull‑up/pull‑down circuit failed