What it means
HVIL loop D 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 high-voltage interlock loop D is a safety circuit whose voltage is monitored by the control module. This code sets when loop D voltage falls below the expected range; a wire shorted to ground is one possible cause. The fault may also interfere with communication used by dependent systems.
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 D, gateway, and CAN faults to see whether the low-voltage condition is isolated.
- Read loop D voltage and status in live data and compare the readings with the manufacturer's specification.
- With the high-voltage system safely disabled according to the vehicle's service procedure, inspect accessible loop D wiring for chafing, crushed insulation, corrosion, or loose connectors.
- Have a qualified technician test loop D for a short to ground and verify continuity using the manufacturer's procedure.
- If network faults appear across modules, check gateway routing and CAN termination before replacing loop D parts.
Common fixes
- Repair loop D wiring that is shorted to ground.
- Clean, secure, or replace a damaged loop D connector or terminal.
- Correct gateway routing if module communication tests identify a gateway fault.
- Repair or replace CAN termination components that fail the manufacturer's specification.
Can I keep driving?
Do not drive if the vehicle shows high-voltage warnings, limp mode, or shutdown symptoms; arrange safe diagnosis. A low loop D signal can disable high-voltage operation, and high-voltage wiring should only be handled by qualified personnel.
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.