Reductant/Regeneration Supply Control Circuit Low
P2063 indicates the selective catalytic reduction (SCR) reductant supply pump is not delivering adequate reductant (DEF/urea) pressure to the injection system. This code sets when the control circuit detects voltage or pressure levels below the manufacturer's specified threshold, preventing proper NOx reduction and risking catalyst damage.
What You Might Notice
- Reduced fuel efficiency
- Excessive black smoke from exhaust
- Diminished engine performance
- Check engine light illumination
- Difficulty starting or rough idle
Most Common Causes
- 1
Defective reductant supply pump
The DEF/urea pump may be failing, overloaded, or not building adequate pressure to deliver reductant to the SCR system.
- 2
Low or contaminated DEF fluid
Insufficient reductant level or poor-quality DEF can cause the pump to lose prime and fail to maintain system pressure.
- 3
Faulty reductant pump relay or control circuit
Damaged wiring, corroded connectors, or a failing relay can prevent proper voltage delivery to the pump motor.
- 4
Clogged reductant lines or filter
Blockages in the DEF delivery system or a saturated reductant filter restrict flow and create pressure loss.
How to Diagnose It
- 1
Check Defective reductant supply pump — The DEF/urea pump may be failing, overloaded, or not building adequate pressure to deliver reductant to the SCR system.
- 2
Check Low or contaminated DEF fluid — Insufficient reductant level or poor-quality DEF can cause the pump to lose prime and fail to maintain system pressure.
- 3
Check Faulty reductant pump relay or control circuit — Damaged wiring, corroded connectors, or a failing relay can prevent proper voltage delivery to the pump motor.
- 4
Check Clogged reductant lines or filter — Blockages in the DEF delivery system or a saturated reductant filter restrict flow and create pressure loss.
How to Fix It
- 1
Check and refill DEF reservoir
Verify the reductant (DEF/urea) tank has adequate fluid level and that it is fresh, uncontaminated fluid. Empty and refill if necessary.
- 2
Inspect and test reductant supply pump
Test the pump's electrical connector for proper voltage, listen for pump operation, and measure system pressure. Replace the pump if it fails to build pressure or respond to electrical input.
- 3
Repair pump control circuit wiring and connectors
Inspect the pump relay, wiring harness, and connectors for corrosion, damage, or loose connections. Clean connectors and repair or replace damaged wiring as needed.
- 4
Flush and clean reductant lines and filter
Remove blockages from DEF delivery lines and replace the reductant filter if clogged. Flush the system with fresh DEF to clear any crystallized deposits.
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