P2057 Reductant Injection Valve Circuit Low Bank 2 Unit 2

P2057 Reductant Injection Valve Circuit Low Bank 2 Unit 2 is a generic OBD-II diagnostic trouble code indicating that the Engine Control Module (ECM), Powertrain Control Module (PCM), or aftertreatment control module has detected an abnormally low electrical signal in the reductant injection valve circuit associated with Bank 2, Unit 2.

In simple terms, the vehicle's computer is not seeing the expected voltage or electrical signal from the circuit controlling the relevant reductant injection valve.

The reductant injection system is part of the diesel exhaust aftertreatment system. It injects a reductant into the exhaust stream to help reduce nitrogen oxide (NOx) emissions. On many modern diesel vehicles, this reductant is Diesel Exhaust Fluid (DEF), commonly known as AdBlue in Europe.

Important: The exact physical meaning of Bank 2 and Unit 2 depends on the vehicle manufacturer and aftertreatment system design. The exact injection valve location should always be confirmed using the manufacturer's service information.

Possible causes of P2057 include:

• Short to ground

• Damaged control wire

• Chafed wiring

• Open or internally shorted valve coil

• Corroded connector

• Water intrusion

• Loose electrical terminal

• Poor ground connection

• Low supply voltage

• Blown fuse

• Faulty relay

• Incorrect wiring repair

• Faulty reductant injection valve

• Failed control-module driver

• Software or calibration problem

P2057 does not automatically mean that the reductant injection valve is defective. The complete electrical circuit should be tested before replacing the valve.

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What Does P2057 Mean?

The code description contains several important terms.

Reductant

Reductant is a fluid used by certain diesel emissions-control systems to reduce pollutants.

On many modern diesel vehicles, the reductant is:

• DEF

• Diesel Exhaust Fluid

• AdBlue

The reductant is injected into the exhaust system and used by the Selective Catalytic Reduction (SCR) system to reduce NOx emissions.

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Injection Valve

The reductant injection valve controls the delivery of reductant into the exhaust system.

The control module determines when and how much reductant should be injected according to:

• Engine load

• Engine speed

• Exhaust temperature

• NOx sensor readings

• SCR catalyst operating conditions

• Reductant pressure

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Bank 2

Bank 2 generally refers to the second engine or exhaust bank.

On many V-type engines:

• Bank 1 contains cylinder number one.

• Bank 2 is the opposite side.

However, the exact definition used by the aftertreatment system should be confirmed using manufacturer information.

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Unit 2

Unit 2 identifies the second relevant component or aftertreatment position in the system.

Depending on the vehicle, this may refer to:

• A second reductant injection valve

• A second dosing unit

• A second SCR system

• A second exhaust aftertreatment section

Do not assume the exact physical location without a manufacturer-specific component-location diagram.

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Circuit Low

"Circuit Low" means the control module has detected a voltage or electrical signal below the expected range.

This is primarily an electrical fault code.

It does not necessarily mean that the reductant injection valve is mechanically closed or that there is insufficient DEF in the tank.

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How Does the Reductant Injection System Work?

A typical SCR system operates approximately as follows:

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

2. The system monitors the reductant level and temperature.

3. A supply system moves reductant toward the dosing system.

4. The control module calculates the required dosing quantity.

5. The reductant injection valve receives an electrical command.

6. The valve opens when commanded.

7. Reductant is injected into the exhaust system.

8. Exhaust heat helps convert the reductant into ammonia-containing compounds.

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

10. NOx sensors monitor system performance.

11. The control module adjusts dosing when necessary.

If the electrical signal in the injection-valve circuit falls below the expected range, P2057 may be stored.

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Why Is Correct Reductant Injection Important?

Correct reductant injection helps:

• Reduce NOx emissions

• Maintain SCR catalyst efficiency

• Control exhaust emissions

• Prevent emissions-system restrictions

If the injection circuit cannot operate correctly, the vehicle may experience emissions-system warnings and, depending on the vehicle, operating restrictions.

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Symptoms of P2057

Check Engine Light

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

The control module may illuminate the warning lamp after detecting the low circuit signal.

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DEF/AdBlue Warning

The vehicle may display a reductant or emissions-system warning.

Possible messages include:

• Check DEF

• Check AdBlue

• DEF system malfunction

• AdBlue system fault

• Exhaust fluid system fault

• Emissions system fault

The exact warning depends on the manufacturer.

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Reduced Engine Power

Some vehicles may reduce engine torque if the SCR system cannot operate correctly.

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Vehicle Speed Restriction

Certain diesel vehicles can eventually impose a speed limitation when an SCR fault remains unresolved.

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Increased NOx Emissions

A circuit problem may prevent correct reductant injection and reduce SCR effectiveness.

This can increase NOx emissions.

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Reductant Dosing Problems

The injection valve may not receive the correct electrical command.

Possible results include:

• Interrupted dosing

• Reduced dosing

• Incorrect dosing

• SCR efficiency problems

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Additional Aftertreatment Fault Codes

P2057 may occur together with codes involving:

• DEF/AdBlue

• Reductant pressure

• NOx sensors

• SCR efficiency

• Reductant injectors

• Aftertreatment modules

• Electrical power supply

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No Noticeable Driving Symptoms

Some vehicles may initially drive normally despite P2057.

The primary fault may initially affect only the emissions-control system.

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Common Causes of P2057

Short to Ground

A short to ground is one of the most important causes of a circuit-low condition.

The control wire may contact:

• Chassis ground

• Engine ground

• Another grounded wire

• A damaged metal component

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Damaged Wiring

The wiring harness can be damaged by:

• High exhaust temperatures

• Vibration

• Abrasion

• Road debris

• Water

• Road salt

Chafed wiring can expose the conductor and cause a short to ground.

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Faulty Reductant Injection Valve

The injection valve may have an internal electrical fault.

Possible problems include:

• Internally shorted coil

• Low coil resistance

• Internal wiring damage

• Electrical short

• Failed internal electronics

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Corroded Connector

Corrosion can increase electrical resistance or interfere with the expected circuit operation.

Inspect for:

• Green corrosion

• White deposits

• Moisture

• Water intrusion

• Bent terminals

• Loose pins

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Water Intrusion

Water inside the connector can create electrical leakage or short circuits.

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Poor Ground Connection

A poor or damaged ground circuit can cause abnormal electrical readings.

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Low System Voltage

A weak battery or charging-system problem can contribute to low electrical signals.

Check:

• Battery voltage

• Charging voltage

• Battery terminals

• Main ground connections

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Blown Fuse

A blown fuse can interrupt a power circuit and, depending on the system design, result in an abnormal low signal.

The reason for the fuse failure should be investigated.

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Faulty Relay

A defective relay may prevent the required voltage from reaching the reductant injection valve.

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Incorrect Wiring Repair

A previous repair may have:

• Connected the wrong wire

• Created a short to ground

• Reversed terminals

• Used an incorrect connector

• Damaged the conductor internally

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Incorrect Replacement Component

An incorrect injection valve may have electrical characteristics that do not match the control system.

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Faulty Control Module Driver

The ECM/PCM or aftertreatment control module may use an electronic driver to control the valve.

A failed driver can create an abnormally low signal.

The module should only be suspected after the external circuit and valve have been tested.

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Software or Calibration Problem

In rare cases, a software or calibration problem may contribute to a recurring circuit fault.

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DEF/AdBlue Contamination

Contaminated or incorrect DEF can cause mechanical and chemical aftertreatment problems.

However, DEF contamination alone does not normally cause a circuit-low electrical code.

P2057 should first be diagnosed as an electrical fault.

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Vehicles Commonly Affected by P2057

P2057 can occur on diesel vehicles equipped with SCR and the relevant multi-bank or multi-unit reductant injection system.

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

• Mercedes-Benz Sprinter

• Volkswagen Touareg TDI

• Volkswagen Transporter

• Audi Q7 TDI

• BMW X5 Diesel

• Peugeot Boxer Diesel

• Citroën Jumper

• Fiat Ducato Diesel

• Iveco Daily

• Renault Master

• Opel Movano

This list is not exhaustive.

Because Bank 2 Unit 2 is system-specific, the exact application should always be confirmed using manufacturer information.

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How Is P2057 Diagnosed?

P2057 should be diagnosed as a circuit-low electrical fault.

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

• Short to ground

• Faulty valve

• Low supply voltage

• Damaged wiring

• Connector problem

• Poor ground

• Blown fuse

• Faulty relay

• Control-module driver problem

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Step 1: Scan for Additional Trouble Codes

Retrieve all stored and pending codes.

Look for related faults involving:

• Reductant injection

• DEF/AdBlue

• Reductant pressure

• Dosing valve

• NOx sensors

• SCR efficiency

• Aftertreatment communication

• Battery voltage

Additional codes can help identify a shared power, ground, or control problem.

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Step 2: Check Freeze-Frame Data

Record the conditions when P2057 was stored.

Useful information may include:

• Engine RPM

• Vehicle speed

• Battery voltage

• Engine load

• Exhaust temperature

• Reductant pressure

• Dosing command

• Aftertreatment status

• NOx sensor readings

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Step 3: Identify Bank 2 Unit 2

Use the manufacturer's component-location information to identify the exact:

• Reductant injection valve

• Connector

• Control wire

• Power circuit

• Ground circuit

• Control module

This step is important because Unit 2 can refer to different physical components depending on the manufacturer.

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Step 4: Inspect the Reductant Injection Valve

Inspect the valve for:

• Physical damage

• Corrosion

• DEF crystallization

• Damaged connector

• Bent terminals

• Water intrusion

DEF crystallization may cause mechanical dosing problems but should not be confused with the electrical cause of P2057.

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Step 5: Inspect Wiring and Connectors

Follow the wiring harness from the injection valve toward the control module.

Look for:

• Chafed insulation

• Melted wires

• Broken conductors

• Short to ground

• Corrosion

• Loose terminals

• Water intrusion

• Incorrect previous repairs

Pay particular attention to areas close to hot exhaust components.

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Step 6: Check Battery and Charging Voltage

Verify that the vehicle's electrical system is operating correctly.

Check:

• Battery condition

• Battery voltage

• Charging voltage

• Battery terminals

• Main grounds

Low system voltage can contribute to circuit-low faults.

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Step 7: Check the Power Supply

Verify that the injection valve receives the correct power supply according to manufacturer specifications.

If the voltage is missing or too low, trace the circuit through:

• Fuse

• Relay

• Wiring

• Connector

• Power distribution system

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Step 8: Check the Ground Circuit

Verify the ground connection where applicable.

A voltage-drop test under load can identify a poor ground connection more effectively than a simple continuity test.

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Step 9: Check for a Short to Ground

With the circuit safely isolated according to manufacturer procedures, test the control wire for an unwanted connection to ground.

A short to ground can cause the circuit signal to remain low.

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Step 10: Check the Control-Wire Continuity

Check continuity between the injection valve connector and the appropriate control-module terminal.

A damaged or high-resistance wire can cause an abnormal low signal.

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Step 11: Test the Injection Valve Resistance

If the manufacturer provides a specification, disconnect the valve and measure the internal coil resistance.

Possible problems include:

• Resistance below specification

• Internal short

• Abnormal coil resistance

Do not use a generic resistance value because specifications vary between vehicles.

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Step 12: Perform an Active Test

If supported by the scan tool, command the reductant injection valve.

Monitor:

• Valve command

• Circuit voltage

• Current flow

• Reductant pressure

• Dosing response

An abnormal low signal during an active test can help identify the failed circuit.

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Step 13: Check the Control Signal

Use an appropriate meter or oscilloscope to inspect the control signal.

Depending on the system, the valve may use:

• Switched power

• Ground-side switching

• PWM control

• Electronic driver control

Compare the signal with the manufacturer's specification.

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Step 14: Check Related Fuses and Relays

Inspect all applicable:

• Fuses

• Relays

• Power distribution circuits

A failed fuse or relay can prevent correct voltage from reaching the circuit.

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Step 15: Check for Intermittent Wiring Problems

Carefully manipulate the wiring harness while monitoring:

• Circuit voltage

• Continuity

• Current

• Control signal

Changes during movement can indicate an internal wiring fault.

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Step 16: Check the Control Module

If the valve, wiring, power supply, ground, fuse, and relay all test correctly, inspect the ECM/PCM or aftertreatment control module.

The output driver may require specialized testing.

Do not replace the control module without confirming the external circuit is operating correctly.

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Step 17: Check Manufacturer Technical Information

Check for:

• Technical Service Bulletins

• Known wiring problems

• Updated components

• Connector issues

• Software updates

• Calibration procedures

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How to Fix P2057

The correct repair depends on the cause of the circuit-low condition.

Repair a Short to Ground

Locate the damaged section of wiring and repair or replace it.

Ensure the repaired wire is protected from:

• Exhaust heat

• Abrasion

• Vibration

• Water

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Repair Damaged Wiring

Repair or replace:

• Chafed wires

• Melted insulation

• Broken conductors

• Corroded wiring

• Incorrect previous repairs

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Repair or Replace the Connector

Replace damaged terminals or connectors.

Make sure the connector seals correctly and terminals have proper contact tension.

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Replace a Blown Fuse

Replace the fuse with the correct rating after identifying the reason for the failure.

Never install a higher-rated fuse.

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Replace a Faulty Relay

Replace the relay if testing shows that it does not provide the required power or control function.

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Repair the Power or Ground Circuit

Repair loose, corroded, or damaged power and ground connections.

Verify the repair with an appropriate voltage-drop test.

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Replace the Reductant Injection Valve

Replace the valve if it has an internal short or fails manufacturer electrical specifications.

Make sure the replacement part is correct for Bank 2 Unit 2.

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Repair the Control Circuit

Repair the control wire or related electrical circuit if testing identifies a short or excessive resistance.

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Repair or Replace the Control Module

If the module's output driver is proven defective, repair or replace the applicable control module according to manufacturer procedures.

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Update Control Module Software

If an applicable software update exists, reprogram the relevant control module.

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Clean or Replace the Injection Valve

If DEF crystallization affects the mechanical operation of the valve, clean or replace the component according to manufacturer procedures.

An electrical circuit-low fault should still be diagnosed separately.

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Perform Required Calibration

After replacing the injection valve or control module, the vehicle may require:

• Reductant system initialization

• Injector adaptation

• Dosing calibration

• DEF system reset

• SCR self-test

• Control module programming

The exact procedure depends on the vehicle.

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Clear the Code and Verify the Repair

After completing the repair:

1. Clear P2057.

2. Run the appropriate aftertreatment self-test.

3. Monitor circuit voltage.

4. Confirm correct valve control.

5. Monitor reductant pressure and dosing.

6. Test-drive the vehicle.

7. Rescan for stored and pending codes.

The repair should only be considered complete when P2057 does not return.

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What Happens If P2057 Is Ignored?

If P2057 prevents the reductant injection valve from operating correctly, the SCR system may not receive the required amount of reductant.

Possible consequences include:

• Check Engine Light

• DEF/AdBlue warning

• Increased NOx emissions

• Reduced SCR efficiency

• Incorrect reductant dosing

• Reduced engine power

• Vehicle speed restrictions

• Additional aftertreatment fault codes

Some vehicles may eventually impose operating restrictions when an SCR fault remains unresolved.

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Can You Drive With P2057?

Short-term driving may be possible if the vehicle starts and operates normally, but P2057 should be diagnosed promptly.

If the vehicle displays:

• DEF/AdBlue warnings

• Emissions-system warnings

• Reduced-power messages

• A speed limitation countdown

service should not be delayed.

Continued driving with the fault can potentially lead to:

• Reduced engine power

• Increased NOx emissions

• SCR system problems

• Vehicle speed limitations

• Additional aftertreatment faults

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Is P2057 a Serious Code?

P2057 is generally considered a moderate-to-high severity emissions-system fault.

The immediate problem is an abnormally low electrical signal in the reductant injection valve circuit for Bank 2 Unit 2.

Although the vehicle may initially continue to drive normally, incorrect reductant injection can compromise SCR operation.

Potential consequences include:

• Increased NOx emissions

• Reduced SCR efficiency

• DEF/AdBlue warnings

• Incorrect reductant dosing

• Reduced engine power

• Vehicle speed restrictions

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P2057 vs. P2058 and P2059

These codes identify different electrical conditions in the reductant injection system.

Code	General Meaning
P2057	Reductant Injection Valve Circuit Low Bank 2 Unit 2
P2058	Reductant Injection Valve Circuit High Bank 2 Unit 2
P2059	Reductant Injection Air Pump Control Circuit Open

P2057 — Circuit Low

The control module detects a voltage or electrical signal below the expected range.

Common causes include:

• Short to ground

• Low supply voltage

• Poor ground

• Damaged wiring

• Faulty valve

• Blown fuse

• Faulty relay

P2058 — Circuit High

The control module detects a voltage or electrical signal above the expected range.

Common causes include:

• Short to battery voltage

• Open circuit on some system designs

• Damaged wiring

• Faulty valve

• Control-module driver problem

P2059 — Circuit Open

P2059 identifies an interrupted electrical path in the reductant injection air pump control circuit.

Although all three codes involve the reductant system, they can refer to different components and different electrical conditions.

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How to Prevent P2057

Not every electrical failure can be prevented, but the risk of related problems can be reduced.

Recommended practices include:

• Use the correct DEF/AdBlue specification.

• Keep electrical connectors clean and properly sealed.

• Repair damaged wiring promptly.

• Keep wiring away from excessive exhaust heat.

• Avoid unnecessary modifications to the aftertreatment wiring.

• Maintain the battery and charging system.

• Address DEF/AdBlue warnings promptly.

• Inspect dosing-system wiring during service.

• Prevent excessive DEF crystallization.

• Use the correct replacement components.

• Follow manufacturer repair procedures.

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Final Thoughts

P2057 Reductant Injection Valve Circuit Low Bank 2 Unit 2 indicates that the vehicle's control system has detected an abnormally low electrical signal in the circuit controlling the relevant reductant injection valve.

The most common causes include:

• Short to ground

• Damaged wiring

• Chafed insulation

• Corroded connector

• Water intrusion

• Loose terminal

• Poor ground

• Low supply voltage

• Blown fuse

• Faulty relay

• Internally shorted injection valve

• Incorrect wiring repair

• Control-module driver failure

• Software or calibration problems

The most important point is that P2057 does not automatically mean the reductant injection valve must be replaced.

Because this is a circuit-low fault, diagnosis should begin by confirming the exact component identified as Bank 2 Unit 2. The wiring, connector, power supply, ground, fuse, relay, and injection valve should then be tested systematically.

The control wire should be checked carefully for a short to ground, while the valve should be tested against the manufacturer's electrical specifications.

If the valve and wiring test correctly but the control signal remains abnormal, the ECM/PCM or aftertreatment control module driver should then be investigated.

Ignoring P2057 can eventually result in DEF/AdBlue warnings, increased NOx emissions, reduced SCR efficiency, incorrect reductant dosing, reduced engine power, vehicle speed restrictions, and additional aftertreatment fault codes.

The correct repair is to identify the source of the low electrical signal, repair the wiring or electrical circuit or replace the failed component, perform any required calibration, clear the code, and verify that the reductant system operates correctly without P2057 returning.