P2064 Reductant / Regeneration Supply Control Circuit High

P2064 Reductant / Regeneration Supply Control Circuit High 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 high electrical signal in the reductant or regeneration supply control circuit.

In simple terms, the vehicle's computer is seeing more voltage than expected in a circuit responsible for controlling or supplying reductant or regeneration-related components.

This code is most commonly associated with modern diesel emissions systems, particularly vehicles equipped with Selective Catalytic Reduction (SCR) and Diesel Exhaust Fluid (DEF/AdBlue) systems. Depending on the vehicle manufacturer, however, the exact component referred to by "reductant/regeneration supply" can differ.

The circuit may be associated with components such as:

• Reductant supply pump

• DEF/AdBlue pump

• Reductant dosing system

• Reductant heater

• Reductant supply control valve

• Reductant tank module

• Regeneration-related supply system

• Wiring and connectors

• Power or control circuit

• Aftertreatment control module

A high circuit code does not automatically mean that the pump or reductant component itself is producing excessive voltage. An open control circuit, short to battery voltage, damaged wiring, incorrect electrical resistance, or a failed driver circuit can also cause P2064.

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What Does P2064 Mean?

The code description contains several important terms.

Reductant

"Reductant" refers to a substance used by the emissions system to help reduce harmful nitrogen oxides (NOx) in the exhaust.

On many diesel vehicles, the reductant is Diesel Exhaust Fluid (DEF), also known as AdBlue in Europe.

DEF is injected into the exhaust upstream of the SCR catalyst. At operating temperature, it helps the SCR system convert NOx into primarily nitrogen and water.

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Regeneration

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

During regeneration, the vehicle raises exhaust temperature so that accumulated particulate matter can be burned.

Some vehicles use fuel or other systems to support regeneration.

Because manufacturers use different aftertreatment architectures, the exact meaning of the "regeneration supply" portion of P2064 can vary.

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Supply Control Circuit

The supply control circuit is the electrical circuit used by the control system to operate or regulate the applicable reductant or regeneration supply component.

Depending on the vehicle, this may involve:

• Power supply

• Ground

• Control signal

• Pump driver

• Valve driver

• Heater control

• Module communication

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High

"High" means that the control module has detected an electrical value, generally voltage or circuit feedback, above the expected range.

Possible causes include:

• Short to battery voltage

• Open circuit

• Failed component

• Incorrect resistance

• Damaged wiring

• Poor connector connection

• Internal module driver fault

The exact electrical diagnosis must follow the vehicle manufacturer's circuit diagram.

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How Does the Reductant System Work?

On an SCR-equipped diesel vehicle, the reductant system typically works as follows:

1. DEF/AdBlue is stored in a dedicated tank.

2. A control module monitors the reductant system.

3. A pump supplies DEF at the required pressure.

4. The reductant travels through supply lines.

5. The dosing system meters the required quantity.

6. The reductant injector sprays DEF into the exhaust.

7. Heat converts the DEF into ammonia-containing compounds.

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

9. NOx sensors monitor system performance.

10. The control system adjusts reductant dosing as necessary.

P2064 can occur when the electrical control of one of the supply-related components does not behave as expected.

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How Does Diesel Regeneration Work?

A DPF captures soot from diesel exhaust.

As soot accumulates, the vehicle must periodically regenerate the filter.

During regeneration:

1. The vehicle detects increasing soot loading.

2. Engine and exhaust conditions are monitored.

3. The control system raises exhaust temperature.

4. Accumulated soot is oxidized.

5. The DPF becomes less restricted.

6. The system returns to normal operation.

Depending on the vehicle, additional fuel delivery, heaters, or other components may be involved in regeneration.

P2064 therefore requires vehicle-specific diagnosis to determine whether the fault concerns the reductant supply system, regeneration supply circuit, or another aftertreatment component.

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Symptoms of P2064

Check Engine Light

The Check Engine Light is one of the most common symptoms.

The warning may appear together with other emissions-system warnings.

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DEF/AdBlue Warning

Vehicles equipped with SCR 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 manufacturer.

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Reduced Engine Power

Some vehicles may enter a reduced-power strategy when an important emissions-system fault is detected.

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Limited Vehicle Speed

Some diesel vehicles may eventually impose a speed limitation if the SCR system cannot operate correctly or if a reductant-system fault remains unresolved.

The exact strategy is manufacturer-specific.

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DPF Regeneration Problems

If P2064 is related to a regeneration supply circuit, the vehicle may have difficulty completing DPF regeneration.

Possible consequences include:

• Increasing soot loading

• More frequent regeneration attempts

• DPF restriction

• Reduced engine performance

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Increased Fuel Consumption

If regeneration becomes abnormal or occurs more frequently, fuel consumption may increase.

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Increased Exhaust Emissions

A malfunctioning reductant or regeneration system can increase emissions.

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Poor Engine Performance

Depending on the fault and the vehicle's fail-safe strategy, symptoms may include:

• Hesitation

• Reduced acceleration

• Limited power

• Poor throttle response

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Warning Messages

The instrument cluster may display an emissions or aftertreatment warning.

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No Noticeable Symptoms

P2064 can sometimes be stored before the driver notices significant performance problems.

The vehicle may continue to drive normally while the control module monitors the fault.

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Common Causes of P2064

Short to Battery Voltage

A short to battery voltage is one of the most important possibilities with a high-circuit code.

If a control or feedback wire contacts a powered circuit, the module may detect a voltage higher than expected.

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Open Circuit

An open circuit can also cause a high signal on certain monitored circuits.

For example, a control module may use a pull-up voltage. If the circuit becomes disconnected, the module can see that voltage and interpret it as a high condition.

Therefore, "circuit high" does not always mean the wire is receiving excessive external voltage.

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Faulty Reductant Pump

The reductant supply pump may have:

• Internal electrical failure

• Incorrect resistance

• Shorted internal windings

• Mechanical seizure

• Internal driver problems

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Faulty Reductant Control Valve

A supply-control valve can fail electrically or mechanically.

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Reductant Heater Problem

DEF systems often include heaters because DEF can freeze at temperatures below its normal operating range.

A heater or heater-control circuit fault may affect the reductant system.

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Damaged Wiring

Aftertreatment wiring is exposed to:

• High exhaust temperatures

• Road debris

• Water

• Salt

• Vibration

• Chemical contamination

Possible problems include:

• Melted insulation

• Chafed wires

• Broken conductors

• Corroded wiring

• Shorted circuits

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Corroded Connectors

Moisture and contamination can cause connector corrosion.

Check for:

• Green corrosion

• White deposits

• Moisture

• Bent pins

• Loose terminals

• Damaged seals

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Poor Electrical Connection

A loose terminal can create an abnormal circuit condition.

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Failed Reductant Tank Module

Some vehicles integrate several components into the DEF/reductant tank assembly.

A failure within the tank module can affect the supply circuit.

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Incorrect Component Resistance

A replacement component with incorrect electrical specifications can cause a high-input condition.

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Regeneration Supply Component Failure

If the vehicle uses a regeneration-related supply component associated with the monitored circuit, its failure can trigger P2064.

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Aftertreatment Control Module Problem

A failed control-module driver may incorrectly apply voltage or interpret the circuit feedback.

This should normally be investigated after the wiring and component have been tested.

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Software or Calibration Problem

A manufacturer software issue can occasionally cause an incorrect fault determination.

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Contaminated or Incorrect Reductant

Incorrect, contaminated, or poor-quality DEF can cause other SCR-related faults.

It is not necessarily the direct cause of a circuit-high condition, but it should be considered when multiple reductant-system codes are present.

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Frozen Reductant

DEF can freeze under sufficiently low temperatures.

Modern systems are designed to manage freezing and thawing, but extreme conditions or heater faults can cause problems.

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

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Vehicles Commonly Affected by P2064

P2064 can occur on diesel vehicles equipped with reductant or regeneration-related emissions systems.

Examples may include:

• Ford F-250 Super Duty

• Ford F-350 Super Duty

• Ford Transit

• 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.

P2064 is a generic OBD-II code, and the exact component monitored by the code can differ between manufacturers and engine platforms.

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How Is P2064 Diagnosed?

P2064 should be diagnosed as an electrical circuit-high fault first.

Replacing the DEF pump or other aftertreatment component without testing the circuit can result in unnecessary repairs.

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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 related codes involving:

• Reductant system

• DEF/AdBlue

• Reductant pump

• Reductant heater

• Dosing system

• NOx sensors

• DPF

• Regeneration

• Aftertreatment control module

• Power supply

• Ground

• Communication

Additional codes are particularly important because P2064 may be part of a larger aftertreatment electrical fault.

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Step 2: Check Freeze-Frame Data

Record the conditions under which P2064 was stored.

Useful information includes:

• Engine speed

• Vehicle speed

• Engine temperature

• Exhaust temperature

• DEF temperature

• Reductant pressure

• Battery voltage

• DPF status

• Regeneration status

This can help determine whether the fault occurs during normal operation, regeneration, or reductant dosing.

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Step 3: Identify the Exact Component and Circuit

Use the manufacturer's service information to determine exactly which component is designated by the Reductant/Regeneration Supply Control Circuit.

Do not assume that P2064 always refers to:

• DEF pump

• DEF injector

• DPF regeneration injector

• Heater

The exact circuit is manufacturer-specific.

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Step 4: Inspect Wiring and Connectors

Inspect the relevant wiring harness.

Look for:

• Melted insulation

• Chafing

• Broken wires

• Corrosion

• Loose terminals

• Damaged connectors

• Water intrusion

Pay particular attention to wiring routed near the exhaust system.

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Step 5: Check for a Short to Voltage

Test the control circuit for unwanted battery voltage.

If battery voltage is present where it should not be, inspect for:

• Wire-to-wire contact

• Harness damage

• Incorrect repairs

• Connector contamination

• Shorted components

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Step 6: Check for an Open Circuit

Test circuit continuity according to the manufacturer's procedure.

An open wire, disconnected connector, or failed terminal can produce a high reading on some circuit designs.

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Step 7: Check Ground Circuits

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

A poor ground can produce abnormal voltage readings and misleading circuit faults.

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Step 8: Monitor Live Data

Use a suitable diagnostic scan tool to monitor:

• Reductant pressure

• Pump command

• Pump feedback

• Reductant temperature

• Heater status

• Dosing command

• Regeneration status

• Circuit voltage where available

Compare actual values with manufacturer specifications.

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Step 9: Activate the Component With a Scan Tool

If supported, use the scan tool's active-test function to command the relevant:

• Pump

• Valve

• Heater

• Supply component

Monitor circuit voltage and feedback while the component is commanded.

A component that fails only when commanded may require additional electrical testing.

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Step 10: Test Component Resistance

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

Look for:

• Open circuit

• Short circuit

• Resistance outside specification

Do not apply generic resistance values because pump, heater, valve, and injector specifications vary by vehicle.

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Step 11: Check Power Supply

Verify that the affected component receives the correct power supply.

Check:

• Supply voltage

• Fuses

• Relays

• Wiring

• Ground

• Voltage drop

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Step 12: Check Control Signal

If the component is controlled electronically, verify that the control signal is present and behaves as specified.

Oscilloscope testing may be required for certain systems.

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Step 13: Inspect the Reductant System

If the vehicle uses DEF/AdBlue, inspect:

• Reductant tank

• Pump module

• Supply lines

• Heater

• Dosing system

• Electrical connectors

Check for obvious damage or contamination.

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Step 14: Check Reductant Quality

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

Do not assume contaminated DEF is responsible for a circuit-high fault without electrical evidence.

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Step 15: Check DPF and Regeneration Status

If P2064 is associated with a regeneration supply circuit, check:

• DPF soot load

• Differential pressure

• Regeneration history

• Exhaust temperature

• Regeneration commands

• Regeneration-related fault codes

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Step 16: Inspect Exhaust Heat Damage

Because aftertreatment wiring is exposed to extreme temperatures, inspect the harness near:

• DPF

• SCR catalyst

• Exhaust pipes

• Turbocharger

• Regeneration components

Melted insulation can cause a short to voltage or other circuit faults.

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Step 17: Check Aftertreatment Control Module

If wiring and components test correctly, investigate the relevant control module.

Check for:

• Driver failure

• Internal electrical fault

• Connector problems

• Communication issues

• Software updates

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Step 18: Check Manufacturer Technical Information

Search the manufacturer's technical information for:

• Technical Service Bulletins

• Known wiring problems

• DEF pump failures

• Reductant heater faults

• Regeneration system issues

• Software updates

• Updated components

• Calibration procedures

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How to Fix P2064

The correct repair depends on the cause.

Repair a Short to Voltage

If the control circuit is shorted to battery voltage, locate the damaged wiring and repair it.

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Repair an Open Circuit

Repair broken conductors, disconnected terminals, or damaged connectors.

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Repair Wiring Near the Exhaust

If heat has damaged the wiring:

• Replace damaged wiring.

• Repair the harness correctly.

• Restore proper heat protection.

• Secure the harness away from hot exhaust components.

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Repair or Replace the Connector

Replace corroded or damaged terminals and connectors as required.

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Replace the Reductant Pump

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

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Replace the Reductant Control Valve

If the supply-control valve has failed electrically or mechanically, replace it.

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Repair or Replace the Reductant Heater

If the heater circuit is the source of the fault, repair the wiring or replace the heater/module as specified.

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Replace the Reductant Tank Module

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

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Repair Regeneration Supply Components

If testing identifies a regeneration-related supply component, repair or replace the affected component.

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Correct DEF/AdBlue Problems

If contaminated or incorrect reductant is identified along with related system faults, drain and refill the system using the correct manufacturer-approved fluid.

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Repair the Aftertreatment Control Module

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

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Update Module Software

If a software update addresses P2064, reprogram the relevant control module.

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Perform Required Calibration

Some replacement components require:

• Reductant pump initialization

• DEF system reset

• Heater calibration

• Dosing-system calibration

• Aftertreatment module programming

• Regeneration procedure

Follow the vehicle-specific service instructions.

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Clear the Code and Verify the Repair

After completing the repair:

1. Clear P2064.

2. Run the applicable system self-test.

3. Monitor the supply-control circuit.

4. Check reductant pressure or component feedback where applicable.

5. Verify that regeneration or reductant dosing operates correctly.

6. Test-drive the vehicle.

7. Rescan for stored and pending codes.

The repair should be considered successful only when the circuit operates within specification and P2064 does not return.

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What Happens If P2064 Is Ignored?

P2064 can become more serious than a simple electrical warning if it prevents the emissions system from operating correctly.

Possible consequences include:

• Check Engine Light

• DEF/AdBlue warning

• Reduced engine power

• Limited vehicle speed

• Failed DPF regeneration

• Increasing DPF soot loading

• Increased emissions

• Increased fuel consumption

• Possible vehicle immobilization or restart restrictions on some SCR-equipped vehicles

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

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Can You Drive With P2064?

Short-term driving may be possible if the vehicle is operating normally, but P2064 should not be ignored.

If the code affects a DEF/SCR supply circuit, continued operation may eventually result in:

• Reduced power

• Emissions-system warnings

• Speed limitations

• DPF/SCR problems

• Restart restrictions on some vehicles

If a DEF warning or countdown is displayed, the problem should be addressed promptly.

If the vehicle is also experiencing severe power loss, overheating, repeated regeneration failures, or multiple aftertreatment warnings, it should be diagnosed as soon as possible.

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Is P2064 a Serious Code?

P2064 is generally considered a moderate-to-high severity emissions-system fault, particularly on diesel vehicles equipped with SCR/DEF systems.

The code describes an electrical circuit problem, but the affected component may be essential to:

• Reductant delivery

• SCR operation

• DPF regeneration

• Emissions control

Ignoring the problem can therefore cause additional aftertreatment faults and potentially expensive component damage.

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P2064 vs. Related Reductant and Regeneration Codes

P2064 belongs to a group of diagnostic trouble codes involving reductant and regeneration supply circuits.

Depending on the vehicle, nearby codes can include faults involving:

• Reductant supply control

• Reductant pump

• Reductant heater

• Reductant injector

• Regeneration supply

• Aftertreatment system performance

Because the exact component assignment is manufacturer-specific, the complete code description and vehicle-specific service information should always be checked before replacing a component.

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P2064 vs. a Circuit Low or Circuit Intermittent Fault

The distinction between circuit-level codes is useful during diagnosis.

Circuit High

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

Common diagnostic areas include:

• Short to voltage

• Open circuit

• Incorrect resistance

• Component failure

• Driver circuit problem

Circuit Low

The control module detects a voltage below the expected range.

Common diagnostic areas include:

• Short to ground

• Low supply voltage

• Component short

• Wiring fault

Circuit Intermittent

The circuit operates normally at times but becomes abnormal under certain conditions.

Common diagnostic areas include:

• Loose connectors

• Damaged terminals

• Broken wires

• Vibration-related faults

• Heat-related wiring damage

This is why the "High" designation in P2064 should direct diagnostic attention toward the electrical characteristics of the circuit rather than immediately assuming a mechanical reductant problem.

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How to Prevent P2064

Not every P2064 fault can be prevented, but proper maintenance can reduce the risk of related aftertreatment problems.

Recommended practices include:

• Use the correct DEF/AdBlue specification when required.

• Do not add diesel fuel or other fluids to the DEF tank.

• Keep reductant connectors protected from contamination.

• Repair exhaust-related wiring damage promptly.

• Keep wiring harnesses secured away from hot exhaust components.

• Address DEF/SCR warning messages promptly.

• Do not ignore repeated DPF regeneration failures.

• Maintain the vehicle according to manufacturer recommendations.

• Use the correct replacement reductant components.

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

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Final Thoughts

P2064 Reductant / Regeneration Supply Control Circuit High indicates that the vehicle's control system has detected an abnormally high electrical condition in a reductant or regeneration-related supply control circuit.

The most important diagnostic possibilities include:

• Short to battery voltage

• Open circuit

• Damaged wiring

• Heat-damaged harness

• Corroded connector

• Poor terminal contact

• Faulty reductant pump

• Failed supply-control valve

• Reductant heater circuit problem

• Reductant tank module failure

• Regeneration supply component fault

• Aftertreatment control-module driver problem

• Software or calibration issue

The most important point is that P2064 does not automatically mean the DEF pump or regeneration component needs to be replaced.

A circuit-high fault can be caused by a short to voltage, an open circuit, a damaged connector, or a control-circuit problem. The exact component involved is also manufacturer-specific.

A proper diagnosis should therefore begin by identifying the exact P2064 circuit on the vehicle, checking for additional trouble codes, inspecting the wiring and connectors, testing power and ground, checking for unwanted voltage, and monitoring the relevant component with a suitable scan tool.

If the code is associated with an SCR/DEF system, delaying the repair can eventually result in reduced engine power, vehicle speed restrictions, increased emissions, failed regeneration, or other aftertreatment problems.

The correct repair is to identify the actual electrical fault, repair or replace the affected component according to the manufacturer's specifications, perform any required calibration or system reset, and verify that the circuit operates normally without P2064 returning.