U3522
High Voltage System Interlock Circuit F Performance.
- Generic
- Network
- Generic code
- High severity
How this code is built
- U
- SystemNetwork
- 3
- Defined bySAE, the same on every car
- 5
- AreaNetwork area 5
- 22
- FaultThe specific fault in that area
What it means
U3522 is the generic code for a performance fault in High Voltage System Interlock Circuit F. The interlock is a low-voltage loop that runs through high-voltage connectors, covers and service disconnects, and it lets the control unit confirm the high-voltage system is safely closed. The control unit has seen the loop signal outside its expected range or behaviour, for example intermittent, out of range or not matching what it expects. Which parts sit on circuit F depends on the model, so check the manufacturer's information for that vehicle.
Symptoms
- Hybrid or EV warning light, or a high-voltage system fault message on the dash
- Vehicle will not go to ready or will not start in electric mode
- Reduced power or limp mode while driving
- High-voltage system shutting down intermittently
- Charging not starting or stopping part way through
- Other high-voltage or communication codes stored alongside it
Possible causes
- Loose, partly seated or contaminated high-voltage connector in the interlock looplikely
- Damaged, chafed or corroded interlock wiring or pins in circuit Flikely
- High-voltage cover, service disconnect or component lid not fitted or seated correctly after recent workpossible
- Water ingress or corrosion in a connector on the interlock looppossible
- Fault inside a high-voltage component that carries the interlock loop, such as the inverter, charger, battery pack or compressor (model dependent)possible
- Fault in the control unit that monitors the interlockrare
How to diagnose
- Check for a safe working procedure and whether you are qualified for high-voltage work. If not, stop here and refer the car to a trained technician.
- Read all stored codes and freeze frame data. Note whether the fault is current or intermittent and what the vehicle was doing when it set.
- Look for recent work, accident damage or underbody impact that could have disturbed high-voltage components, covers or connectors.
- With the high-voltage system isolated using the manufacturer's procedure, visually inspect the interlock connectors and covers on circuit F for poor seating, damage, moisture or corrosion.
- Check the interlock wiring for chafing, pin damage, pushed-back terminals and water ingress. Wiggle-test the harness while watching live data if the fault is intermittent.
- Use the manufacturer's wiring information to identify which components are on circuit F, then test loop continuity and resistance as specified.
- Clear the code after repair and recheck live data. Confirm the fault does not return after a road test and a charge cycle if applicable.
How to fix
- Reseat and secure the affected high-voltage connectors and covers, ensuring locking mechanisms engage fully
- Repair or replace damaged interlock wiring, terminals or connectors, following the manufacturer's repair procedure
- Clean up and dry out connectors affected by moisture or corrosion, and replace any that are damaged, then find and fix the source of the water
- Replace the faulty high-voltage component or its interlock switch if testing shows the loop is broken inside it
- Replace or repair the monitoring control unit only if all wiring and components test good and the manufacturer's diagnosis confirms it
Can I keep driving?
Do not keep driving with a high-voltage warning or reduced power, as the system may shut down without notice and the interlock is a safety feature. Have it recovered or inspected by a trained high-voltage technician, and never bypass the interlock.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.