U351E

What it means

U351E is a generic code meaning the High Voltage System Interlock Circuit E is not performing as expected. The interlock (HVIL) is a low-voltage safety loop that runs through high-voltage connectors, covers and components so the system can confirm everything is properly connected before and while the high-voltage contactors are closed. The control unit saw the loop signal intermittent, out of range, or not matching the expected pattern. Which components 'Circuit E' covers depends on the make, model and system layout, so check the manufacturer's wiring information.

Symptoms

• Hybrid or electric system warning light or message on the dashboard
• Vehicle will not enter Ready mode or will not start
• Reduced power or limp mode, or loss of drive while moving
• Charging will not start or stops part way through
• Intermittent fault that comes and goes with vibration, bumps or temperature
• Other high-voltage or communication codes stored alongside it

Possible causes

• Loose, poorly seated or corroded interlock connector at a high-voltage component or service disconnectlikely
• Damaged, chafed or broken interlock loop wiring, or a terminal with poor tension or water ingresslikely
• High-voltage component cover, connector or service disconnect incorrectly refitted after recent work or an accident repairpossible
• Faulty interlock switch or loop circuit inside a high-voltage component (for example inverter, charger, battery pack or compressor), depending on modelpossible
• Low-voltage supply or earth problem affecting the control unit that monitors the looppossible
• Fault in the monitoring control unit, or outdated software where the manufacturer lists it as a known causerare

How to diagnose

1. Confirm the technician is trained and authorised for high-voltage work, and follow the manufacturer's safe isolation procedure before touching any orange high-voltage parts.
2. Read all stored and pending codes and freeze frame data to see when the fault set and whether other high-voltage or network codes are present.
3. Find out whether any recent work, collision repair or component removal has been done that could have disturbed a connector or cover.
4. Use the manufacturer's wiring information to identify what Circuit E covers on this model and which connectors and components are in the loop.
5. Visually inspect the loop connectors, covers and wiring for damage, corrosion, moisture, bent pins or incomplete locking.
6. With the system isolated, test the interlock loop for continuity, resistance and short to earth or supply against the manufacturer's specification.
7. Check the low-voltage battery condition and the supply and earth to the monitoring control unit.
8. Clear the code, then recheck with a wiggle test and road test to see if it returns, and check for any applicable software updates for the model.

How to fix

• Reseat, clean or replace the affected interlock connector and ensure all locking tabs are fully engaged.
• Repair or replace damaged interlock wiring or terminals, using the manufacturer's approved repair method.
• Refit any high-voltage covers or service disconnects correctly, and replace damaged seals.
• Replace the high-voltage component or interlock switch if the fault is proven inside it.
• Repair low-voltage supply or earth faults, or replace the low-voltage battery if it is weak.
• Update or replace the monitoring control unit only after the wiring and components are proven good, or where a known software fault applies.

Can I keep driving?

Nearby codes

• U351DGenericHigh Voltage System Interlock Circuit E
• U351FGenericHigh Voltage System Interlock Circuit E Low