A high-voltage interlock connector that is not fully seated, corroded, or has damaged terminals.; A broken or chafed interlock wire in the harness, often near a hinge point or a high-voltage component.; A faulty high-voltage component cover or service disconnect plug that is not properly installed, interrupting the interlock loop.; A defective high-voltage component (such as the battery pack, inverter, or charger) with an internal interlock switch failure.; Water intrusion or contamination in a high-voltage connector causing the interlock circuit to short or go open.; A malfunctioning high-voltage control module or battery energy control module that misreads the interlock signal.

DTC codes / U35xx · Network communication / U3522

U3522High Voltage System Interlock Circuit F Performance

Q: What does code U3522 mean?

High Voltage System Interlock Circuit F Performance. U3522 is a generic manufacturer-specific code indicating that the high-voltage system interlock circuit has failed a performance test, typically because the voltage on the loop is outside the expected range or the circuit is not completing its safety check. The computer monitors this low-voltage loop that runs through high-voltage connectors and covers; when the signal does not match the expected profile, it sets this code to disable the high-voltage system and prevent electric shock.

U3522 is a generic manufacturer-specific code indicating that the high-voltage system interlock circuit has failed a performance test, typically because the voltage on the loop is outside the expected range or the circuit is not completing its safety check. The computer monitors this low-voltage loop that runs through high-voltage connectors and covers; when the signal does not match the expected profile, it sets this code to disable the high-voltage system and prevent electric shock.

SystemNetwork

Code typeGeneric (all makes)

SeverityHigh

Fix difficultyProfessional

AreaNetwork communication

Symptoms you may notice

The high-voltage system may be disabled, preventing the vehicle from starting or driving in electric mode.
A red high-voltage warning light or a service vehicle soon message appears on the dashboard.
The vehicle may enter a reduced power mode or refuse to shift into gear.
Often no symptoms besides the warning light, especially if the fault is intermittent.
The high-voltage contactors may not close, so the vehicle will not go into 'ready' mode.
Other high-voltage system codes may be stored alongside U3522.

Common causes, most likely first

A high-voltage interlock connector that is not fully seated, corroded, or has damaged terminals.
A broken or chafed interlock wire in the harness, often near a hinge point or a high-voltage component.
A faulty high-voltage component cover or service disconnect plug that is not properly installed, interrupting the interlock loop.
A defective high-voltage component (such as the battery pack, inverter, or charger) with an internal interlock switch failure.
Water intrusion or contamination in a high-voltage connector causing the interlock circuit to short or go open.
A malfunctioning high-voltage control module or battery energy control module that misreads the interlock signal.

How to diagnose and fix it

Inspect all high-voltage connectors and covers for proper seating, corrosion, or damage, and reseat any that are suspect.
Check the interlock circuit wiring for continuity and shorts using a multimeter, following the manufacturer's service information for pinouts and expected values.
Verify that the high-voltage service disconnect plug is fully engaged and that its interlock switch is functioning.
Scan all modules for related codes and perform a bidirectional test of the interlock circuit if the scan tool supports it.
If the circuit tests good, substitute a known-good high-voltage component only if the service manual allows, to isolate an internal interlock failure.
Repair or replace any damaged wiring, connectors, or components found during diagnosis, then clear codes and verify the high-voltage system powers up correctly.

Interlock faults that fool good technicians

A common oversight is assuming the interlock loop is a simple switch when it is often a low-voltage signal that must be within a specific voltage window; a partial short or high resistance can set U3522 without any visible damage.
The code can be set by a high-voltage component that is mechanically fine but has an internal interlock switch that fails only when hot or vibrating, so intermittent codes require wiggle tests and freeze-frame data review.
After any high-voltage repair, the interlock circuit must be fully verified before the contactors will close; simply clearing the code will not restore power if the underlying fault remains.
Some vehicles use a daisy-chained interlock loop through multiple components, so one faulty connector anywhere in the chain can disable the entire high-voltage system and set this code.
U3522 is often stored alongside insulation fault or high-voltage isolation codes, and diagnosing only the interlock circuit without checking for isolation faults can lead to a comeback.

Can I keep driving with U3522?

Do not continue driving with this code because the high-voltage system may be disabled or in a unsafe state, and attempting to drive could lead to a loss of power or electric shock risk. Have the vehicle inspected by a qualified high-voltage technician before further use.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.