What it means
HVIL loop G timing/pattern does not match expected behavior. 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 G monitors whether its covered connectors and components remain properly connected. This performance code means the loop G signal behavior does not follow the expected pattern, which can result from intermittent contact at an HV connector.
Common causes
Most likely first.
- Intermittent contact in HV connector
- 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 note whether U3526 occurs with vibration, temperature changes, or other interlock and communication faults.
- With the vehicle safely powered down per manufacturer instructions, inspect accessible loop G connectors and wiring for looseness, chafing, corrosion, or intermittent-contact damage.
- Use scan-tool live data, if available, to monitor loop G status under approved conditions and compare it with other loops.
- Have a qualified high-voltage technician test loop G connector contact and circuit behavior using the manufacturer's procedures and specifications.
- If loop G remains stable, investigate intermittent gateway routing or CAN termination faults using vehicle-specific wiring information.
Common fixes
- Reseat a loose loop G connector following the manufacturer's procedure.
- Repair chafed or corroded loop G wiring and terminals.
- Replace a connector or interlock component confirmed to have intermittent contact.
- Repair gateway routing or CAN termination only if testing verifies the fault.
Can I keep driving?
An intermittent interlock fault can lead to reduced power or shutdown while driving, so stop using the vehicle if warnings or drivability changes appear. Arrange inspection by a qualified high-voltage technician.
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.