P2063 Reductant / Regeneration Supply Control Circuit Low

P2063 Reductant / Regeneration Supply Control Circuit Low is a generic OBD-II diagnostic trouble code indicating that the vehicle's Engine Control Module (ECM/PCM) or aftertreatment control system has detected an abnormally low electrical signal in the reductant or regeneration supply control circuit.

In simple terms, the vehicle's computer is detecting less voltage or electrical response than expected from a circuit responsible for controlling a reductant or regeneration-related component.

The code is commonly associated with modern diesel emissions systems, particularly vehicles equipped with Selective Catalytic Reduction (SCR) and Diesel Exhaust Fluid (DEF/AdBlue) systems. However, the exact component monitored by P2063 depends on the vehicle manufacturer and engine application.

Possible components involved include:

• Reductant supply pump

• DEF/AdBlue pump

• Reductant supply control valve

• Reductant heater

• Reductant tank module

• Dosing system

• Regeneration-related supply component

• Aftertreatment control circuit

• Wiring and connectors

Possible causes include:

• Short to ground

• Low supply voltage

• Faulty reductant pump

• Failed control valve

• Failed reductant heater

• Damaged wiring

• Corroded connector

• Poor electrical connection

• High-resistance wiring

• Internal fuel/DEF tank module fault

• Failed control-module driver

• Incorrectly installed component

• Software or calibration problem

A circuit-low code does not automatically mean the reductant pump itself is defective. The wiring and power/ground circuits should be tested before replacing expensive aftertreatment components.

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What Does P2063 Mean?

The code description contains several important terms.

Reductant

"Reductant" refers to a fluid used by certain exhaust aftertreatment systems to reduce harmful nitrogen oxide (NOx) emissions.

On many diesel vehicles, the reductant is Diesel Exhaust Fluid (DEF), called AdBlue in many European markets.

DEF is injected into the exhaust system upstream of the SCR catalyst. Under the correct exhaust conditions, it helps the SCR system convert NOx into primarily nitrogen and water.

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Regeneration

"Regeneration" refers to the process used to remove accumulated soot from a Diesel Particulate Filter (DPF).

The vehicle periodically raises exhaust temperature so that trapped particulate matter can be oxidized.

Depending on the engine design, additional fuel, heaters, or other supply components may be used to support regeneration.

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Supply Control Circuit

This refers to the electrical circuit used to operate or regulate the applicable reductant or regeneration supply component.

It may contain:

• Power supply

• Ground

• Control wire

• Pump driver

• Valve driver

• Heater circuit

• Feedback circuit

• Control module

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Low

"Low" means that the control module has detected a circuit voltage or feedback value below its expected range.

Common electrical possibilities include:

• Short to ground

• Low supply voltage

• High resistance

• Poor ground

• Failed component

• Damaged wiring

• Connector problem

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How Does the Reductant System Work?

A typical SCR/DEF system operates approximately as follows:

1. DEF is stored in a dedicated tank.

2. The control system monitors DEF temperature and system conditions.

3. A reductant pump draws fluid from the tank.

4. The pump creates the required supply pressure.

5. DEF travels through the supply line.

6. A dosing module controls the amount injected into the exhaust.

7. The reductant injector sprays DEF into the exhaust stream.

8. DEF is converted into ammonia-containing compounds.

9. The SCR catalyst uses these compounds to reduce NOx.

10. NOx sensors monitor the effectiveness of the process.

11. The control system adjusts reductant dosing as required.

P2063 can occur if the electrical circuit controlling a supply-related component is pulled below its expected voltage.

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How Does DPF Regeneration Work?

The DPF captures soot produced by diesel combustion.

As soot accumulates, exhaust restriction increases and the vehicle eventually performs regeneration.

During regeneration:

1. The control system calculates or estimates soot loading.

2. Engine operating conditions are monitored.

3. Exhaust temperature is increased.

4. Accumulated soot is oxidized.

5. DPF restriction is reduced.

6. The system returns to normal operation.

Depending on the vehicle, fuel dosing, heaters, or other regeneration-related components can be involved.

Because P2063 can be assigned differently by different manufacturers, the exact component must be identified using vehicle-specific service information.

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Symptoms of P2063

Check Engine Light

The Check Engine Light may illuminate after the control module detects the low-circuit condition.

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DEF/AdBlue Warning

SCR-equipped vehicles may display a reductant warning.

Possible messages include:

• Check DEF

• AdBlue system fault

• DEF system malfunction

• Exhaust fluid system fault

• Reductant system fault

The exact wording depends on the vehicle.

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Reduced Engine Power

Some diesel vehicles can enter a reduced-power or torque-limiting strategy when the emissions system cannot operate correctly.

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Vehicle Speed Limitation

Some SCR-equipped vehicles may eventually limit vehicle speed if an unresolved reductant-system fault remains active.

The exact strategy varies by manufacturer.

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DPF Regeneration Problems

If P2063 concerns a regeneration-related supply circuit, the vehicle may have difficulty completing DPF regeneration.

This can lead to:

• Increasing soot load

• More frequent regeneration attempts

• DPF restriction

• Reduced engine performance

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Increased Fuel Consumption

Repeated unsuccessful regeneration attempts can increase fuel consumption.

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Increased Emissions

A malfunctioning reductant or regeneration system can increase exhaust emissions.

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Poor Engine Performance

Depending on the vehicle's fail-safe strategy, possible symptoms include:

• Reduced acceleration

• Hesitation

• Limited power

• Poor throttle response

• Torque reduction

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Warning Messages

The instrument cluster may display an emissions or aftertreatment warning.

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No Noticeable Symptoms

P2063 may initially be stored without obvious drivability symptoms.

The vehicle can sometimes continue operating normally while the control system monitors the fault.

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Common Causes of P2063

Short to Ground

A short to ground is one of the most important possibilities with a circuit-low code.

If a control or signal wire contacts ground, circuit voltage can be pulled below the expected level.

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Low Supply Voltage

A weak battery, charging-system problem, blown fuse, relay issue, or damaged power wire can cause insufficient voltage at the affected component.

Possible causes include:

• Weak battery

• Alternator problem

• Blown fuse

• Faulty relay

• Corroded power connection

• High-resistance wiring

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Faulty Reductant Pump

A reductant supply pump can develop internal electrical problems.

Possible failures include:

• Shorted windings

• Excessive current draw

• Internal motor failure

• Internal electrical resistance problem

• Mechanical seizure

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Faulty Reductant Control Valve

A supply-control valve may fail electrically or mechanically.

A shorted valve coil can pull the control circuit low.

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Reductant Heater Failure

DEF systems commonly use heaters because DEF can freeze at sufficiently low temperatures.

A shorted heater or heater circuit can create an abnormal electrical load and cause a circuit-low condition.

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Damaged Wiring

Aftertreatment wiring is exposed to harsh conditions, including:

• High exhaust temperatures

• Road debris

• Water

• Salt

• Vibration

• Chemical contamination

Possible wiring faults include:

• Melted insulation

• Chafed wires

• Broken conductors

• Short to ground

• High resistance

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Corroded Connectors

Moisture and contamination can cause corrosion in reductant-system connectors.

Check for:

• Green corrosion

• White deposits

• Moisture

• Bent terminals

• Loose pins

• Damaged seals

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High-Resistance Connection

A poor connection can create a significant voltage drop.

Possible causes include:

• Corroded terminals

• Loose terminals

• Damaged connector

• Partially broken wire

A component may receive insufficient voltage even though the circuit does not have a direct short.

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Failed Reductant Tank Module

Some vehicles integrate the pump, heater, sensors, and control electronics into the reductant tank module.

A fault within the module can trigger P2063.

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Regeneration Supply Component Failure

If the vehicle assigns P2063 to a regeneration-related supply circuit, a defective supply component can cause the code.

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Aftertreatment Control Module Driver Fault

The control module may contain an internal transistor or driver circuit that controls the affected component.

A failed driver can produce a low-circuit condition.

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Incorrect Component

A recently replaced pump, heater, valve, or module may have the wrong electrical specifications.

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Incorrect Installation

Check whether:

• Connectors are fully seated.

• Wiring is routed correctly.

• Components are installed in the correct position.

• Grounds are properly connected.

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Software or Calibration Problem

In rare cases, incorrect software or calibration can cause a valid electrical condition to be interpreted incorrectly.

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Contaminated or Incorrect DEF

Incorrect or contaminated DEF can cause SCR-related faults.

However, it should not automatically be considered the cause of a circuit-low fault. P2063 is primarily an electrical circuit diagnosis.

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Frozen DEF

DEF can freeze at low temperatures.

Modern systems are designed to manage freezing, but a heater fault can prevent normal thawing.

A frozen tank does not by itself prove that the electrical circuit is faulty.

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Vehicles Commonly Affected by P2063

P2063 can occur on diesel vehicles equipped with reductant or regeneration-related supply systems.

Examples may include:

• Ford F-250 Super Duty

• Ford F-350 Super Duty

• Ford F-450 Super Duty

• Ford Transit Diesel

• Chevrolet Silverado Duramax

• Chevrolet Express Diesel

• GMC Sierra Duramax

• GMC Savana Diesel

• Ram 2500

• Ram 3500

• Jeep Grand Cherokee Diesel

• Jeep Wrangler Diesel

• Mercedes-Benz Sprinter

• Mercedes-Benz E-Class Diesel

• Volkswagen Touareg TDI

• Volkswagen Transporter

• Audi Q7 TDI

• BMW X5 Diesel

• BMW X6 Diesel

• Peugeot Boxer Diesel

• Citroën Jumper

• Fiat Ducato Diesel

• Iveco Daily

• Renault Master

• Opel Movano

This list is not exhaustive.

The exact component associated with P2063 depends on the manufacturer, engine, emissions system, and vehicle configuration.

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How Is P2063 Diagnosed?

P2063 should be approached as an electrical circuit-low fault.

The goal is to determine whether the low signal is caused by:

• A short to ground

• Low supply voltage

• Excessive voltage drop

• A shorted component

• Damaged wiring

• Connector problems

• Control-module failure

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Step 1: Scan for Additional Trouble Codes

Use a suitable diagnostic scan tool to retrieve stored and pending codes.

Look for additional codes involving:

• Reductant system

• DEF/AdBlue

• Reductant pump

• Reductant heater

• Dosing system

• NOx sensors

• DPF

• Regeneration

• Aftertreatment module

• Power supply

• Ground

• Communication

If several components report low-circuit faults simultaneously, a shared power or ground problem should be considered.

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Step 2: Check Freeze-Frame Data

Record the conditions under which P2063 was stored.

Useful information includes:

• Engine RPM

• Vehicle speed

• Battery voltage

• Engine temperature

• Exhaust temperature

• DEF temperature

• Reductant pressure

• Regeneration status

• Dosing status

This can help determine whether the fault occurs during startup, dosing, heating, or regeneration.

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Step 3: Identify the Exact P2063 Circuit

Use the manufacturer's wiring diagram and service information to determine the component associated with the Reductant/Regeneration Supply Control Circuit.

Do not automatically assume P2063 refers to the DEF pump.

Depending on the vehicle, the monitored circuit may involve a:

• Pump

• Valve

• Heater

• Supply component

• Regeneration component

• Tank module

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Step 4: Inspect Fuses and Relays

Check the relevant:

• Fuses

• Relays

• Power feeds

• Ground points

A failed fuse or relay can prevent the affected component from receiving the correct voltage.

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Step 5: Inspect Wiring and Connectors

Inspect the circuit for:

• Chafing

• Melted insulation

• Broken wires

• Corrosion

• Loose terminals

• Water intrusion

• Damaged connectors

Pay particular attention to harnesses routed close to the exhaust.

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Step 6: Check for a Short to Ground

Disconnect the appropriate component according to the manufacturer's diagnostic procedure.

Then test the control circuit for an unwanted connection to ground.

A shorted wire can pull the circuit voltage down and trigger P2063.

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Step 7: Measure Supply Voltage

Check the voltage available at the affected component.

Compare it with the manufacturer's specification.

A low supply can be caused by:

• Weak battery

• Charging problem

• Poor relay

• Blown fuse

• High-resistance wire

• Corroded terminal

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Step 8: Perform a Voltage-Drop Test

Voltage-drop testing is especially useful for high-resistance connections.

Check the:

• Power side

• Ground side

• Connectors

• Relays

• Wiring

An apparently good wire can still cause a large voltage drop when current flows.

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Step 9: Monitor Live Data

Use a suitable scan tool to monitor relevant parameters such as:

• Reductant pressure

• Pump command

• Pump feedback

• Reductant temperature

• Heater status

• Dosing command

• Regeneration status

• Component voltage where available

Compare actual values with manufacturer specifications.

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Step 10: Activate the Component

If supported, use an active test to command the relevant:

• Pump

• Valve

• Heater

• Supply component

Monitor circuit voltage and current during activation.

A component that causes voltage to collapse when commanded may be internally shorted or drawing excessive current.

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Step 11: Test Component Resistance

If the manufacturer specifies a resistance test, disconnect the component and measure resistance across the appropriate terminals.

Look for:

• Short circuit

• Open circuit

• Resistance outside specification

Do not use a generic resistance value because pump, heater, valve, and dosing-component specifications differ.

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Step 12: Check Ground Connections

Verify that the affected component and control module have proper ground connections.

A poor ground can produce voltage-drop problems and cause misleading circuit faults.

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Step 13: Inspect the Reductant Tank Module

If the vehicle uses an integrated DEF/reductant tank module, inspect:

• Pump

• Heater

• Internal wiring

• Electrical connector

• Sensors

• Module electronics

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Step 14: Check the Regeneration System

If the vehicle's service information associates P2063 with regeneration supply, inspect:

• Regeneration supply component

• DPF soot load

• Exhaust temperature

• Differential pressure

• Regeneration history

• Regeneration commands

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Step 15: Check Exhaust Heat Damage

Inspect wiring around:

• DPF

• SCR catalyst

• Exhaust pipes

• Turbocharger

• Regeneration components

Heat-damaged insulation can create shorts to ground.

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Step 16: Check Control Module Driver

If the component and wiring are confirmed good, check the control module's output driver.

This may require:

• Voltage testing

• Current testing

• Oscilloscope testing

• Manufacturer-specific module tests

Do not condemn the control module until the wiring and component have been verified.

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Step 17: Check DEF Quality

If additional SCR codes are present, verify that the correct DEF/AdBlue specification is being used.

However, do not replace electrical components simply because DEF quality is questionable.

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Step 18: Check Manufacturer Technical Information

Look for:

• Technical Service Bulletins

• Known reductant pump failures

• DEF heater issues

• Wiring harness problems

• Regeneration system faults

• Software updates

• Updated components

• Calibration procedures

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How to Fix P2063

The repair depends on the actual cause identified during diagnosis.

Repair a Short to Ground

If the supply-control circuit is shorted to ground, locate the damaged section and repair the wiring.

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Repair Damaged Wiring

Repair or replace:

• Chafed wires

• Broken conductors

• Melted insulation

• Corroded wiring

• Damaged harness sections

Restore proper heat protection where necessary.

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Repair or Replace Connectors

Replace damaged terminals or connectors and restore proper sealing.

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Repair the Power Supply

If the circuit has insufficient voltage, repair:

• Fuse

• Relay

• Power wire

• Battery connection

• Ground connection

• High-resistance terminal

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Replace the Reductant Pump

If testing confirms that the reductant supply pump is internally defective, replace the appropriate pump or module.

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Replace the Reductant Control Valve

If the valve is shorted or otherwise defective, replace it.

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Repair or Replace the Reductant Heater

If a heater circuit has failed, repair the wiring or replace the heater/module according to the manufacturer's procedure.

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Replace the Reductant Tank Module

If the pump, heater, sensors, or control electronics are integrated into the tank module and the module is defective, the complete assembly may need replacement.

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Repair Regeneration Supply Components

If P2063 is assigned to a regeneration-related supply component, repair or replace the affected component.

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Repair the Aftertreatment Control Module

If the control module's driver circuit is confirmed defective, repair or replace the module according to manufacturer procedures.

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Update Control Module Software

If a manufacturer software update addresses P2063, reprogram the applicable module.

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Perform Required Calibration

After replacing a reductant or aftertreatment component, the vehicle may require:

• Reductant system initialization

• DEF system reset

• Pump calibration

• Heater calibration

• Dosing-system calibration

• Aftertreatment module programming

• Regeneration procedure

The exact requirements are vehicle-specific.

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Clear the Code and Verify the Repair

After completing the repair:

1. Clear P2063.

2. Run the applicable system self-test.

3. Monitor the supply-control circuit.

4. Check component voltage and current where applicable.

5. Verify reductant pressure or feedback.

6. Confirm dosing or regeneration operates correctly.

7. Test-drive the vehicle.

8. Rescan for stored and pending codes.

The repair should be considered successful only when the circuit operates within specification and P2063 does not return.

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What Happens If P2063 Is Ignored?

P2063 can become more serious if it prevents the vehicle's emissions system from operating correctly.

Possible consequences include:

• Check Engine Light

• DEF/AdBlue warning

• Reduced engine power

• Vehicle speed limitation

• Failed DPF regeneration

• Increasing DPF soot load

• Increased exhaust emissions

• Increased fuel consumption

• Additional SCR/aftertreatment fault codes

• Possible restart restrictions on some vehicles

The exact consequences depend on the vehicle's emissions strategy.

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Can You Drive With P2063?

Short-term driving may be possible if the vehicle is operating normally, but P2063 should be diagnosed promptly.

If the fault affects the DEF/SCR supply system, continued driving can eventually result in:

• Reduced engine power

• Speed restrictions

• Emissions-system warnings

• DPF/SCR problems

• Restart restrictions on some vehicles

If a DEF/AdBlue countdown or warning is displayed, the repair should not be delayed.

If the vehicle has severe power loss, repeated regeneration failures, overheating, or multiple aftertreatment warnings, it should be inspected as soon as possible.

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Is P2063 a Serious Code?

P2063 is generally considered a moderate-to-high severity emissions-system fault.

The immediate problem is an electrical circuit-low condition, but the affected circuit may control an important reductant or regeneration component.

If the system cannot deliver reductant or perform required regeneration, continued operation can cause additional aftertreatment problems.

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P2063 vs. P2064

P2063 and P2064 describe opposite electrical conditions in the same general reductant/regeneration supply circuit family.

Code	General Meaning
P2063	Reductant/Regeneration Supply Control Circuit Low
P2064	Reductant/Regeneration Supply Control Circuit High

P2063 — Circuit Low

The control module detects a voltage or feedback value below the expected range.

Important diagnostic areas include:

• Short to ground

• Low supply voltage

• High-resistance connection

• Failed component

• Poor ground

• Damaged wiring

P2064 — Circuit High

The control module detects a voltage or feedback value above the expected range.

Important diagnostic areas include:

• Short to battery voltage

• Open circuit

• Incorrect resistance

• Failed component

• Control-circuit problem

The two codes can therefore involve the same component but require different electrical tests.

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How to Prevent P2063

Not every P2063 fault can be prevented, but proper maintenance can reduce the risk of related aftertreatment problems.

Recommended practices include:

• Use the correct DEF/AdBlue specification.

• Keep reductant connectors clean and protected.

• Repair damaged wiring promptly.

• Keep wiring harnesses secured away from hot exhaust components.

• Address DEF/SCR warning messages promptly.

• Do not ignore repeated DPF regeneration problems.

• Maintain the battery and charging system properly.

• Avoid unnecessary modifications to aftertreatment wiring.

• Use the correct replacement reductant components.

• Follow manufacturer procedures after replacing pumps, heaters, valves, or tank modules.

• Maintain the vehicle according to manufacturer recommendations.

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Final Thoughts

P2063 Reductant / Regeneration Supply Control Circuit Low indicates that the vehicle's control system has detected an abnormally low electrical condition in a reductant or regeneration-related supply control circuit.

The most important diagnostic possibilities include:

• Short to ground

• Low supply voltage

• High-resistance connection

• Poor ground

• Damaged wiring

• Corroded connector

• Faulty reductant pump

• Failed control valve

• Reductant heater fault

• Reductant tank module failure

• Regeneration supply component problem

• Aftertreatment control-module driver failure

• Software or calibration issue

The most important point is that P2063 does not automatically mean the DEF pump needs to be replaced.

A circuit-low fault can originate from a short to ground, insufficient power supply, excessive voltage drop, damaged wiring, poor connector contact, or an internally shorted component.

Diagnosis should therefore begin with the exact P2063 circuit identified for the vehicle. The technician should check the related fuses and relays, power and ground circuits, wiring, connectors, voltage drop, component resistance, and live-data behavior before condemning the pump, heater, valve, or control module.

If P2063 is associated with an SCR/DEF system, ignoring the fault can eventually lead to reduced engine power, vehicle speed restrictions, failed regeneration, increased emissions, and potentially restart restrictions.

The correct repair is to identify the actual low-voltage cause, repair or replace the affected component, perform any required calibration or system reset, and verify that the reductant or regeneration system operates correctly without P2063 returning.