A high-voltage interlock connector that is not fully seated or has a loose terminal; Corrosion or water intrusion in an interlock connector or splice, increasing resistance and voltage drop; Damaged interlock wiring harness, such as a chafed or broken wire, often near a service disconnect or battery pack; Faulty high-voltage component cover or service plug that is not properly installed, keeping the interlock loop open; Internal failure in a high-voltage component, such as the battery pack, inverter, or motor, affecting the interlock circuit; Failed interlock switch or sensor within a high-voltage connector; Control module software error or faulty module causing a false high-voltage reading on the interlock circuit

DTC codes / U35xx · Network communication / U351E

U351EHigh Voltage System Interlock Circuit E Performance

Q: What does code U351E mean?

High Voltage System Interlock Circuit E Performance. U351E indicates that the high-voltage system interlock circuit for loop E has reported a voltage above the expected range, which the vehicle's control module interprets as a potential safety breach. The interlock is a low-voltage loop that runs through high-voltage connectors and covers; when a connector is opened or a cover is removed, the loop breaks and the voltage reading changes, prompting the module to disable the high-voltage system to prevent shock hazard.

U351E indicates that the high-voltage system interlock circuit for loop E has reported a voltage above the expected range, which the vehicle's control module interprets as a potential safety breach. The interlock is a low-voltage loop that runs through high-voltage connectors and covers; when a connector is opened or a cover is removed, the loop breaks and the voltage reading changes, prompting the module to disable 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 under electric power
Illumination of the high-voltage warning light or service vehicle soon message on the dashboard
Reduced power or limp-home mode if the vehicle is a hybrid and can still run on the combustion engine
Audible alert or chime indicating a high-voltage fault
Often no symptoms besides the warning light if the fault is intermittent or stored but not active

Common causes, most likely first

A high-voltage interlock connector that is not fully seated or has a loose terminal
Corrosion or water intrusion in an interlock connector or splice, increasing resistance and voltage drop
Damaged interlock wiring harness, such as a chafed or broken wire, often near a service disconnect or battery pack
Faulty high-voltage component cover or service plug that is not properly installed, keeping the interlock loop open
Internal failure in a high-voltage component, such as the battery pack, inverter, or motor, affecting the interlock circuit
Failed interlock switch or sensor within a high-voltage connector
Control module software error or faulty module causing a false high-voltage reading on the interlock circuit

How to diagnose and fix it

Use a scan tool to read all high-voltage system codes and freeze-frame data to determine if the fault is active or stored
Visually inspect all high-voltage interlock connectors and covers for proper seating, damage, or corrosion, starting with the easiest to access
Perform a voltage drop test on the interlock circuit at the connector pins to check for excessive resistance
Check service information for the specific interlock circuit E routing and test continuity and voltage at each segment
Inspect the high-voltage battery pack service disconnect plug and ensure it is fully engaged and undamaged
If the fault persists, follow the manufacturer's diagnostic flow chart to test the interlock switch or module, and repair or replace as needed
After repair, clear codes and verify the interlock circuit voltage is within specification and the high-voltage system re-enables

Interlock Circuit E: What Most Techs Overlook

A common oversight is assuming the interlock fault is inside the high-voltage battery, when often it is simply a partially unlatched connector at the inverter or motor that was disturbed during previous service.
The interlock circuit is a low-voltage loop, so a high-voltage reading on circuit E can be caused by a poor ground connection at the control module rather than a high-voltage component failure.
Some vehicles set U351E when the 12-volt battery is weak or during low-voltage conditions, because the module misreads the interlock voltage reference, so always verify 12-volt system health first.
After any high-voltage repair, the interlock circuit must be reinitialized or the code will remain stored even if the physical fault is fixed, so follow the manufacturer's reset procedure.
Do not probe high-voltage interlock circuits with a standard test light; use a high-impedance digital multimeter to avoid damaging sensitive module inputs.

Can I keep driving with U351E?

Do not drive the vehicle with an active U351E code, as the high-voltage system may be disabled or in a unsafe state. If the vehicle is a hybrid and still moves under engine power, limit driving to moving the vehicle to a safe location for diagnosis, and avoid touching any orange high-voltage cables or components.

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.