Damaged or disconnected electrical connector at the reductant injector; Open or shorted wiring in the reductant injector circuit, including chafed or broken wires; Failed reductant injector solenoid with an open internal coil; Corroded or loose pins in the injector or PCM connector; Blown fuse or faulty relay supplying power to the reductant injector circuit; Faulty powertrain control module driver for the injector circuit, though rare

DTC codes / P20xx · Fuel and air metering and auxiliary emission controls / P2056

P2056Reductant Injector Circuit/Open (Bank 2 Unit 2)

Q: What does code P2056 mean?

Reductant Injector Circuit/Open (Bank 2 Unit 2). P2056 indicates that the powertrain control module has detected an open circuit or excessive resistance in the reductant injector circuit for bank 2 unit 2 of the selective catalytic reduction system. This injector is responsible for spraying diesel exhaust fluid into the exhaust stream to reduce nitrogen oxide emissions, and an open circuit means the injector is not receiving the electrical command to operate.

P2056 indicates that the powertrain control module has detected an open circuit or excessive resistance in the reductant injector circuit for bank 2 unit 2 of the selective catalytic reduction system. This injector is responsible for spraying diesel exhaust fluid into the exhaust stream to reduce nitrogen oxide emissions, and an open circuit means the injector is not receiving the electrical command to operate.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering and auxiliary emission controls

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms
Reduced engine power or limp mode triggered by the emissions system
A message on the dashboard indicating low diesel exhaust fluid or a emissions system fault
Increased diesel exhaust fluid consumption if the injector is stuck open or leaking
Rough running or misfire in extreme cases due to excessive reductant injection
Failed emissions test due to incomplete SCR system readiness

Common causes, most likely first

Damaged or disconnected electrical connector at the reductant injector
Open or shorted wiring in the reductant injector circuit, including chafed or broken wires
Failed reductant injector solenoid with an open internal coil
Corroded or loose pins in the injector or PCM connector
Blown fuse or faulty relay supplying power to the reductant injector circuit
Faulty powertrain control module driver for the injector circuit, though rare

How to diagnose and fix it

Inspect the reductant injector connector for corrosion, damage, or loose pins and clean or repair as needed
Check the wiring harness for the reductant injector circuit for continuity and short to ground or power using a multimeter
Test the reductant injector resistance with a multimeter and compare to the manufacturer's specification
Verify power and ground signals at the injector connector with the key on and engine running
Check the fuse and relay that supply power to the reductant injector circuit and replace if faulty
If the circuit and injector test good, diagnose the PCM driver circuit or reprogram/replace the PCM as last resort
Clear the diagnostic trouble codes and perform a road test to verify the repair and ensure the monitor runs

Reductant injector circuit checks that save time

A common oversight is assuming the injector itself is faulty when the actual problem is a corroded connector or chafed wire near the exhaust, where heat and vibration take a toll.
The code can set intermittently due to a loose ground connection for the SCR system, so always check ground points before condemning the injector.
Some vehicles require a relearn or adaptation reset after replacing the reductant injector, and skipping this step can cause the code to return immediately.
P2056 specifically refers to bank 2 unit 2, so on vehicles with multiple reductant injectors, misdiagnosing the wrong injector is a common trap; always confirm the bank and unit location in the service information.
A failed reductant injector can also cause P20B9 or P20BA codes, so scanning all modules for related codes helps confirm the root cause.

Can I keep driving with P2056?

You can usually drive the vehicle with P2056 set, but the SCR system will not function correctly, leading to increased emissions and possible limp mode if the fault worsens. Avoid long trips and heavy loads until the repair is completed, and do not ignore the code as it can lead to more extensive emissions system damage.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.