P2055 Reductant Injection Valve Circuit High Bank 1 Unit 2

P2055 Reductant Injection Valve Circuit High Bank 1 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 high electrical signal in the reductant injection valve circuit associated with Bank 1, Unit 2.

In simple terms, the vehicle's computer has detected that the electrical voltage or control signal for the relevant reductant injection valve is higher than expected.

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 meaning and physical location of Bank 1 and Unit 2 can vary significantly depending on the vehicle manufacturer and aftertreatment system design. The exact component location should always be confirmed using manufacturer-specific service information.

Possible causes of P2055 include:

• Short to battery voltage

• Short to a power circuit

• Broken control wire

• Open circuit

• Damaged wiring

• Faulty reductant injection valve

• Open or internally damaged valve coil

• Corroded connector

• Disconnected connector

• Incorrect wiring repair

• Faulty power supply

• Damaged relay

• Incorrect replacement component

• Faulty control-module driver

• Software or calibration problem

P2055 does not automatically mean that the reductant injection valve is defective. The electrical circuit should be tested completely before replacing the valve.

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What Does P2055 Mean?

The code description contains several important parts.

Reductant

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

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 flow of reductant into the exhaust system.

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

• Engine load

• Engine speed

• Exhaust temperature

• NOx sensor readings

• SCR catalyst conditions

• Reductant pressure

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Bank 1

Bank 1 generally refers to the engine or exhaust side associated with cylinder number one.

On V-type engines:

• Bank 1 = side containing cylinder number one

• Bank 2 = opposite side

However, in some complex aftertreatment systems, the manufacturer's definition of the bank should always be confirmed.

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Unit 2

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

Depending on the vehicle, Unit 2 may refer to:

• A second reductant injection valve

• A second dosing valve

• A second exhaust aftertreatment unit

• A second SCR dosing location

The exact location must be confirmed using manufacturer-specific service information.

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Circuit High

"Circuit High" means the control module has detected a voltage or electrical signal above the expected operating range.

This does not necessarily mean that the reductant injection valve is mechanically stuck open.

P2055 primarily indicates an electrical circuit problem.

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How Does the Reductant Injection System Work?

A typical SCR system operates as follows:

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

2. The system monitors reductant level and temperature.

3. A supply pump 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 required.

7. DEF 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 the system's performance.

11. The control module adjusts dosing when necessary.

If the control module detects an abnormally high signal in the relevant injection-valve circuit, P2055 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 aftertreatment-system restrictions

If the injection valve circuit cannot operate correctly, the SCR system may not receive the required reductant.

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Symptoms of P2055

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 high circuit signal.

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DEF/AdBlue Warning

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

Possible messages include:

• Check DEF

• Check AdBlue

• DEF system malfunction

• AdBlue system fault

• Exhaust fluid system fault

• Emissions system fault

The exact message depends on the manufacturer.

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Reduced Engine Power

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

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Vehicle Speed Restriction

Certain diesel vehicles may eventually impose a speed limitation if an SCR fault remains unresolved.

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Increased NOx Emissions

If the reductant injection valve cannot operate correctly, SCR performance may be reduced.

This can increase NOx emissions.

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Incorrect Reductant Dosing

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

P2055 may occur together with codes involving:

• DEF/AdBlue

• Reductant pressure

• NOx sensors

• SCR efficiency

• Reductant injection valves

• Aftertreatment modules

• Electrical power supply

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No Noticeable Driving Symptoms

Some vehicles may initially drive normally.

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

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Common Causes of P2055

Short to Battery Voltage

A short to battery voltage is one of the most important causes of a circuit-high condition.

The control wire may contact:

• Battery power

• Ignition voltage

• A power-supply circuit

• Another positively energized wire

This can cause the control-module input to remain abnormally high.

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Open Control Circuit

Depending on the electrical design, a broken or disconnected control wire can also produce a high voltage reading.

Some systems use internal pull-up circuits, meaning an open circuit may appear as a high signal.

Therefore, a circuit-high code does not always mean the wire is directly shorted to battery voltage.

The exact circuit design must be checked using manufacturer information.

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Damaged Wiring

The wiring harness can be damaged by:

• High exhaust temperatures

• Vibration

• Abrasion

• Road debris

• Water

• Road salt

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Faulty Reductant Injection Valve

The injection valve may have an internal electrical failure.

Possible problems include:

• Open valve coil

• Internal electrical damage

• Connector failure

• Internal wiring failure

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Corroded Connector

Corrosion can interfere with the electrical connection.

Check for:

• Green corrosion

• White deposits

• Water intrusion

• Bent terminals

• Loose terminals

• Damaged seals

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Disconnected Connector

A connector that is not fully seated can interrupt the expected electrical circuit.

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Incorrect Wiring Repair

A previous repair may have:

• Connected the control wire to the wrong circuit

• Connected a control wire to battery voltage

• Reversed terminals

• Left an important wire disconnected

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Faulty Power Supply

An abnormal power supply can create a circuit-high condition depending on the circuit design.

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Faulty Relay

A defective relay may cause abnormal voltage to reach the injection-valve circuit.

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Incorrect Replacement Component

An incorrect reductant injection valve may have different electrical characteristics.

This can cause the control module to detect an abnormal circuit condition.

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Faulty Control Module Driver

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

A failed driver can create an abnormal high signal.

The module should not be replaced until the valve, wiring, connectors, and power circuits have been tested.

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Software or Calibration Problem

In rare cases, incorrect module software or calibration can contribute to a recurring circuit fault.

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DEF/AdBlue Contamination

Contaminated or incorrect DEF can cause mechanical dosing and SCR problems.

However, DEF contamination alone does not normally cause an electrical circuit-high code.

P2055 should first be diagnosed as an electrical problem.

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Vehicles Commonly Affected by P2055

P2055 can occur on diesel vehicles equipped with SCR and the relevant reductant injection valve configuration.

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 1 Unit 2 is system-specific, the exact component should always be confirmed using manufacturer information.

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How Is P2055 Diagnosed?

P2055 should be diagnosed as a circuit-high electrical fault.

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

• Short to battery voltage

• Open circuit

• Faulty valve

• Damaged wiring

• Connector problem

• Incorrect power supply

• 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

• Dosing valve

• Reductant pressure

• NOx sensors

• SCR efficiency

• Aftertreatment module

• Electrical power supply

Additional codes may identify a shared electrical problem.

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Step 2: Check Freeze-Frame Data

Record the conditions when P2055 was stored.

Useful information may include:

• Engine RPM

• Vehicle speed

• Battery voltage

• Engine load

• Exhaust temperature

• Reductant pressure

• Dosing command

• NOx sensor values

• Aftertreatment operating status

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Step 3: Identify Bank 1 Unit 2

Use manufacturer-specific component-location information.

Identify the exact:

• Reductant injection valve

• Connector

• Control wire

• Power circuit

• Ground circuit

• Controlling module

This is essential because Unit 2 does not have a universal physical location.

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Step 4: Inspect the Reductant Injection Valve

Check for:

• Physical damage

• Corrosion

• DEF crystallization

• Connector damage

• Bent terminals

• Water intrusion

DEF crystallization can cause mechanical problems but should not be confused with the electrical cause of P2055.

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Step 5: Inspect Wiring and Connectors

Follow the harness from the injection valve toward the controlling module.

Look for:

• Melted insulation

• Broken wires

• Chafed wiring

• Short to power

• Corrosion

• Loose connectors

• Incorrect previous repairs

Pay particular attention to wiring routed near 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 voltage

• Charging voltage

• Battery terminals

• Main power connections

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Step 7: Check the Power Supply

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

An abnormal power supply may contribute to a high circuit condition.

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Step 8: Check the Ground Circuit

Verify the ground circuit where applicable.

A poor ground can create abnormal electrical behavior.

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Step 9: Check for a Short to Battery Voltage

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

A short to power can cause the signal to remain abnormally high.

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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 broken wire can produce a high signal on some circuit designs.

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Step 11: Test the Injection Valve Resistance

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

Possible results include:

• Open circuit

• Excessively high resistance

• Resistance outside specification

An open coil may cause an abnormal circuit reading.

Do not use a generic resistance specification because values 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

If the control module commands the valve but the electrical signal remains abnormally high, further circuit testing is required.

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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 manufacturer specifications.

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Step 14: Check Related Fuses and Relays

Inspect the applicable:

• Fuses

• Relays

• Power-distribution circuits

A faulty power-control component can create abnormal voltage conditions.

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Step 15: Check for Intermittent Faults

Carefully manipulate the wiring harness while monitoring the circuit.

Look for changes in:

• Voltage

• Continuity

• Current

• Control signal

This can identify an internal wire break or loose electrical connection.

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Step 16: Check the Control Module

If the valve, wiring, power supply, ground, and connectors test correctly, check the ECM/PCM or aftertreatment module.

The module's output driver may require specialized diagnostic equipment.

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Step 17: Check Manufacturer Technical Information

Check for:

• Technical Service Bulletins

• Known wiring problems

• Connector faults

• Updated dosing valves

• Software updates

• Calibration procedures

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How to Fix P2055

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

Repair a Short to Power

Locate the section where the control wire contacts a positive-voltage source.

Repair or replace the damaged wiring.

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Repair Damaged Wiring

Repair or replace:

• Melted wires

• Chafed wires

• Broken conductors

• Corroded wiring

• Incorrect previous repairs

Restore proper harness routing and heat protection.

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Repair or Replace the Connector

Replace damaged terminals or connectors.

Ensure proper terminal tension and connector sealing.

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Replace the Reductant Injection Valve

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

The replacement component must be correct for Bank 1 Unit 2.

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Repair the Power or Ground Circuit

Repair any damaged power or ground connection found during diagnosis.

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Replace a Faulty Relay

Replace the relay if it does not operate according to specification.

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Repair the Control Circuit

Repair the damaged control wire or electrical driver circuit.

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Repair or Replace the Control Module

If the 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 a software update addresses P2055, reprogram the relevant control module.

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Clean or Replace the Dosing Valve

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

Electrical faults should be repaired separately.

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Perform Required Calibration

After replacing a reductant injection valve, the vehicle may require:

• Reductant system initialization

• Dosing calibration

• Injector adaptation

• DEF system reset

• Aftertreatment module programming

• SCR self-test

The exact procedure is vehicle-specific.

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Clear the Code and Verify the Repair

After completing the repair:

1. Clear P2055.

2. Run the appropriate aftertreatment self-test.

3. Monitor the valve control signal.

4. Check circuit voltage.

5. Confirm correct valve operation.

6. Monitor reductant pressure and dosing.

7. Test-drive the vehicle.

8. Rescan for stored and pending codes.

The repair should only be considered complete when P2055 does not return.

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What Happens If P2055 Is Ignored?

If P2055 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

On some vehicles, continued operation with an unresolved SCR fault can eventually result in operating limitations.

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Can You Drive With P2055?

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

If the vehicle displays a DEF/AdBlue warning, reduced-power message, emissions countdown, or speed limitation warning, service should not be delayed.

Continued driving can potentially result in:

• Reduced engine power

• Increased emissions

• SCR system problems

• Vehicle speed limitations

• Additional aftertreatment faults

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Is P2055 a Serious Code?

P2055 is generally considered a moderate-to-high severity emissions-system fault.

The immediate problem is an abnormally high electrical signal in the reductant injection valve circuit for Bank 1 Unit 2.

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

Potential consequences include:

• Increased NOx emissions

• Reduced SCR efficiency

• DEF/AdBlue warnings

• Incorrect reductant dosing

• Reduced engine power

• Vehicle speed limitations

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P2055 vs. P2056, P2057 and P2058

These codes identify different electrical conditions affecting the reductant injection valve circuit.

Code	General Meaning
P2055	Reductant Injection Valve Circuit High Bank 1 Unit 2
P2056	Reductant Injection Valve Circuit Open Bank 2 Unit 2
P2057	Reductant Injection Valve Circuit Low Bank 2 Unit 2
P2058	Reductant Injection Valve Circuit High Bank 2 Unit 2

P2055 and P2058 both indicate a circuit-high condition, but they apply to different bank and unit locations.

P2056 identifies an open circuit, while P2057 identifies a low electrical signal.

Because bank and unit identification varies by manufacturer, always confirm the exact component before replacing any parts.

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How to Prevent P2055

Not every electrical failure can be prevented, but proper maintenance can reduce the risk of related faults.

Recommended practices include:

• Use the correct DEF/AdBlue specification.

• Keep electrical connectors clean and sealed.

• Repair damaged wiring promptly.

• Protect wiring from excessive exhaust heat.

• Avoid unnecessary modifications to the aftertreatment wiring.

• Address DEF/AdBlue warnings promptly.

• Inspect the dosing valve during aftertreatment service.

• Address DEF crystallization when necessary.

• Use the correct replacement components.

• Follow manufacturer procedures after repairs.

• Maintain the battery and charging system.

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Final Thoughts

P2055 Reductant Injection Valve Circuit High Bank 1 Unit 2 indicates that the vehicle's control system has detected an abnormally high electrical signal in the circuit controlling the relevant reductant injection valve.

The most common causes include:

• Short to battery voltage

• Short to a power circuit

• Open circuit

• Broken control wire

• Damaged wiring

• Corroded connector

• Disconnected connector

• Faulty injection valve

• Open valve coil

• Faulty power supply

• Incorrect wiring repair

• Faulty relay

• Control-module driver failure

• Incorrect replacement component

• Software or calibration problems

The most important point is that P2055 does not automatically mean the reductant injection valve needs to be replaced.

Because this is a circuit-high fault, diagnosis should begin with the electrical system. The exact component identified as Bank 1 Unit 2 should first be confirmed using manufacturer information. The technician should then inspect the valve, connector, wiring, power supply, ground, and control signal.

The circuit should be checked for a short to battery voltage and, depending on the system design, for an open circuit.

If the valve has an internal open or abnormal electrical condition, replacement may be required. If the valve and wiring test correctly, the control module and output driver should be investigated.

Ignoring P2055 can eventually lead to DEF/AdBlue warnings, increased NOx emissions, reduced SCR efficiency, incorrect reductant dosing, reduced engine power, vehicle speed limitations, and additional aftertreatment faults.

The correct repair is to identify the source of the abnormal high 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 P2055 returning.