U352F
High Voltage System Interlock Circuit J Low.
- 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
- 2F
- FaultThe specific fault in that area
What it means
U352F means the control unit monitoring the high voltage interlock loop (HVIL) has seen the signal on interlock circuit J reading low, meaning below the expected voltage range. The interlock is a low voltage safety loop that proves HV connectors, covers and components are secure. Which part of the vehicle circuit J covers depends on the make, model and system design, so check the manufacturer's wiring information.
Symptoms
- Hybrid, EV or high voltage system warning light on the dashboard
- Vehicle will not enter Ready mode or the HV contactors will not close
- Reduced power or limp mode
- Loss of HV charging or DC fast charging not starting
- Other HV or communication fault codes stored alongside
Possible causes
- Interlock wiring shorted to ground, for example chafed or pinched loop wiringlikely
- Damaged, contaminated or corroded interlock pins in an HV connector or service disconnectlikely
- Water ingress or moisture in an HV component connector causing a low signalpossible
- Previous repair or collision damage affecting the interlock harness or an HV componentpossible
- Fault inside an HV component that is part of loop J, such as a charger, inverter or compressorpossible
- Fault in the monitoring control unit or its interlock driver circuitrare
How to diagnose
- Only trained HV-qualified staff should work on this; follow the manufacturer's HV isolation and safe working procedure before disconnecting any orange HV connector or component.
- Read all stored codes and freeze frame data, noting whether the fault is current or intermittent and what other HV codes are present.
- Check the manufacturer's wiring information to identify which connectors and components are in interlock circuit J for this model.
- Visually inspect the loop harness and connectors for chafing, crush damage, water, corrosion, bent pins or loose covers, including any recent repair areas.
- With the HV system isolated, check the loop for a short to ground and for correct resistance and continuity against manufacturer specifications.
- Check the service disconnect and each HV connector in the loop is fully seated and latched with pins making good contact.
- Isolate sections of the loop one component at a time, following the manufacturer's procedure, to find where the low signal is coming from.
- Clear the code after repair and road test, then recheck for the code returning and confirm the system enters Ready mode normally.
How to fix
- Repair or replace the shorted or damaged interlock wiring section.
- Replace damaged or corroded interlock connectors or terminals, and fit new seals where needed.
- Dry out and properly seal any connector with water ingress, then replace parts that are corroded.
- Replace the HV component that is pulling the interlock loop low, once confirmed by testing.
- Replace or reprogram the monitoring control unit only if the loop is proven good and the manufacturer's diagnostics point to the unit.
Can I keep driving?
Do not rely on driving the car: the HV system may shut down or refuse to start, and a fault in the HV safety loop should be treated seriously. Have it inspected by an HV-trained technician before further use.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.