What it means
HVIL loop O voltage below expected range. A communication loss with this module breaks any function relying on its data — diagnostic tools may show 'no response' and dependent modules can fall into limp mode.
At a glance
- Usually lights the warning light of the system that lost communication
- The engine or gearbox may go into limp mode
How it works
The HVIL checks that high-voltage connectors and covers are safely engaged. The module monitors loop O voltage; this code sets when the signal is below its expected range, which can indicate a short to ground or another circuit fault pulling the signal low.
Common causes
Most likely first.
- Interlock wire shorted to ground
- Gateway module routing CAN messages incorrectly
- CAN terminating resistor (120 Ω) drifted out of spec
Symptoms
- Multiple warning lights may illuminate
- Affected modules may go into limp mode or shut down
- Specific functions inoperative depending on module
- Diagnostic tools may show communication faults
How to diagnose it
- Record freeze-frame data and scan all modules for loop O, other HVIL, and communication codes before clearing the fault.
- Check loop O live voltage or status and compare it with the manufacturer's specification under the recorded conditions.
- With the high-voltage system safely disabled according to the service procedure, inspect accessible loop O wiring for pinched insulation, grounding contact, moisture, or corrosion.
- Have a qualified technician test the isolated loop O circuit for a short to ground and verify continuity as directed by the manufacturer.
- If circuit tests pass, check gateway routing and CAN termination only if the remaining communication codes support a network fault.
Common fixes
- Repair loop O wiring that is shorted to ground.
- Clean or replace a corroded or damaged loop O connector.
- Repair any chafed harness section found during inspection.
- Correct gateway or CAN termination faults only when network tests confirm them.
Can I keep driving?
Do not drive if the vehicle reports a high-voltage warning, reduced power, or shutdown; the low loop O signal may cause high-voltage functions to be disabled. Leave circuit testing and repairs to a technician trained for high-voltage systems.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.