What it means
Reductant/regeneration supply control line stuck high — short to B+ or open ground. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The reductant/regeneration supply control circuit operates a vehicle-specific DEF supply or regeneration component. The control module monitors its voltage when it commands the circuit. P2064 sets when the circuit stays higher than expected, which can result from a short to battery voltage or an open ground path.
Common causes
Most likely first.
- Short to B+
- Connector pins corroded - high contact resistance
- Supply wire pinched against B+ source
Symptoms
- Check engine light or NOx warning on
- AdBlue/DEF level or quality warning
- Possible no-start countdown after ignore period
- Failed emissions inspection (NOx)
How to diagnose it
- Save freeze-frame data and check related reductant supply or regeneration codes to identify the conditions when the high voltage was recorded.
- Use the vehicle's wiring diagram to identify the affected circuit, component and ground path.
- Inspect the harness for pinched or chafed wiring that could contact a battery-positive source, and check the connector for moisture, corrosion or displaced pins.
- Test the control wire for a short to battery voltage and check the ground path using the manufacturer's procedure.
- If wiring and grounds are sound, test the affected supply or regeneration component and its control device.
Common fixes
- Repair wiring pinched against a battery-positive source and secure the harness.
- Clean and reconnect corroded or loose terminals.
- Repair a damaged ground wire or connector terminal.
- Replace the affected supply or regeneration component if testing confirms it is faulty.
Can I keep driving?
The vehicle may remain drivable, but the affected DEF supply or regeneration function may not work correctly and NOx emissions can increase. Address the fault promptly, particularly if the vehicle displays an SCR warning or countdown.
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.