Damaged or corroded interlock connector pins or terminals in the high-voltage circuit; Faulty interlock switch or sensor integrated into a high-voltage component cover; Chafed or shorted interlock wiring harness, often near a service disconnect or component connector; Water intrusion or contamination in a high-voltage connector causing abnormal voltage; Internal failure of the component module that monitors the interlock circuit; Loose or improperly seated high-voltage connector after recent service; Voltage supply or ground issue affecting the interlock circuit reference voltage

DTC codes / U35xx · Network communication / U353F

U353FHigh Voltage System Interlock Circuit N Low

Q: What does code U353F mean?

High Voltage System Interlock Circuit N Low. U353F indicates that the high-voltage system interlock circuit for a specific component or zone (designated 'N') is reporting a voltage that is higher than expected, which the control module interprets as a potential safety concern. The interlock is a low-voltage loop that runs through high-voltage connectors and covers; when its voltage is out of range, the vehicle disables the high-voltage system to prevent shock hazard.

U353F indicates that the high-voltage system interlock circuit for a specific component or zone (designated 'N') is reporting a voltage that is higher than expected, which the control module interprets as a potential safety concern. The interlock is a low-voltage loop that runs through high-voltage connectors and covers; when its voltage is out of range, the vehicle disables the high-voltage system to prevent shock hazard.

SystemNetwork

Code typeGeneric (all makes)

SeverityHigh

Fix difficultyProfessional

AreaNetwork communication

Symptoms you may notice

High-voltage system disabled, preventing the vehicle from starting or moving
Warning light or message on the dashboard indicating a high-voltage fault
Often no symptoms besides the warning light, with the vehicle operating normally until the next key cycle
Reduced power or limp mode if the vehicle is already in motion when the fault sets
Inability to engage the high-voltage battery contactors or charge the battery
Other high-voltage related codes stored in multiple modules

Common causes, most likely first

Damaged or corroded interlock connector pins or terminals in the high-voltage circuit
Faulty interlock switch or sensor integrated into a high-voltage component cover
Chafed or shorted interlock wiring harness, often near a service disconnect or component connector
Water intrusion or contamination in a high-voltage connector causing abnormal voltage
Internal failure of the component module that monitors the interlock circuit
Loose or improperly seated high-voltage connector after recent service
Voltage supply or ground issue affecting the interlock circuit reference voltage

How to diagnose and fix it

Inspect all high-voltage connectors and covers for proper seating, corrosion, or damage, especially those related to circuit 'N'
Check the interlock circuit wiring for continuity, shorts to voltage, and resistance against manufacturer specifications
Measure the interlock circuit voltage at the monitoring module and compare to expected values
Test the interlock switch or sensor within the suspect component for correct operation
Repair or replace damaged wiring, terminals, or connectors as needed
If the interlock circuit is integrated into a component, replace that component according to service information
Clear codes and perform a road test to verify the repair, ensuring the high-voltage system re-enables

Interlock circuit faults often misdiagnosed

A common mistake is replacing the high-voltage battery or major component when the fault is simply a loose interlock connector pin that can be repaired.
The interlock circuit is a low-voltage loop; a high voltage reading on it often indicates a short to voltage from a nearby circuit rather than a high-voltage insulation failure.
Some vehicles set this code after a low-voltage battery disconnect or jump start, and it may clear after a few drive cycles if no hard fault exists.
The 'N' designation refers to a specific interlock circuit; always consult the service manual for the exact location, as it varies by manufacturer and model.
After any high-voltage component service, the interlock circuit must be properly reconnected; a partially latched connector can set this code intermittently.

Can I keep driving with U353F?

Do not drive the vehicle if the high-voltage system is disabled, as it may lose power unexpectedly or fail to start. If the vehicle is drivable but the warning is present, avoid high-voltage charging and seek professional diagnosis immediately.

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.