Damaged or corroded wiring harness at the reductant injector connector, especially at the bank 2 unit 2 location; Failed reductant injector with an open or shorted internal coil; Blown fuse or faulty relay supplying power to the reductant injector circuit; Chafed or pinched wire between the injector and the powertrain control module causing a short to ground; Loose or corroded ground connection for the reductant injection system; Faulty powertrain control module driver circuit, though this is rare

DTC codes / P20xx · Fuel and air metering and auxiliary emission controls / P2057

P2057Reductant Injector Circuit Low (Bank 2 Unit 2)

Q: What does code P2057 mean?

Reductant Injector Circuit Low (Bank 2 Unit 2). P2057 indicates that the powertrain control module has detected an abnormally low voltage or current draw on the reductant injector circuit for bank 2 unit 2, which is part of the diesel exhaust fluid injection system on engines with two SCR catalyst banks. The computer monitors the injector driver circuit and sets this code when the signal falls below the expected threshold, typically indicating a short to ground, an open circuit, or a failed injector coil.

P2057 indicates that the powertrain control module has detected an abnormally low voltage or current draw on the reductant injector circuit for bank 2 unit 2, which is part of the diesel exhaust fluid injection system on engines with two SCR catalyst banks. The computer monitors the injector driver circuit and sets this code when the signal falls below the expected threshold, typically indicating a short to ground, an open circuit, or a failed injector coil.

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 powertrain control module to protect the emissions system
A message on the dashboard indicating low diesel exhaust fluid level or a fault in the emissions system
Increased diesel exhaust fluid consumption if the injector is stuck open or leaking
Rough running or misfire in extreme cases if the injector shorts internally and affects shared power supply
Failed state emissions inspection due to the stored trouble code

Common causes, most likely first

Damaged or corroded wiring harness at the reductant injector connector, especially at the bank 2 unit 2 location
Failed reductant injector with an open or shorted internal coil
Blown fuse or faulty relay supplying power to the reductant injector circuit
Chafed or pinched wire between the injector and the powertrain control module causing a short to ground
Loose or corroded ground connection for the reductant injection system
Faulty powertrain control module driver circuit, though this is rare

How to diagnose and fix it

Inspect the reductant injector connector and wiring for corrosion, damage, or loose pins, and repair as needed
Check the fuse and relay for the reductant injector circuit and replace any failed components
Measure resistance across the reductant injector coil and compare to the manufacturer's specification to identify an open or shorted injector
Perform a voltage drop test on the power and ground circuits to the injector to locate excessive resistance
Disconnect the powertrain control module and check for continuity or short to ground on the injector control wire
Replace the reductant injector if testing confirms it is faulty
Clear the code and perform a road test to verify the repair and ensure the monitor runs to completion

Reductant injector circuit low voltage pitfalls

A low voltage code on a reductant injector is often caused by a poor connection at the injector connector rather than a failed injector, so always inspect the pins and seals before condemning the part.
The bank 2 unit 2 designation means this injector is on the second SCR catalyst bank, and on some engines it is difficult to access, leading technicians to overlook a chafed harness behind the engine block.
A shorted reductant injector can draw down the shared power supply and set companion codes for other injectors or sensors on the same circuit, so check for multiple codes before replacing parts.
Diesel exhaust fluid crystallization at the injector tip can cause an intermittent low voltage signal that only appears under certain temperature conditions, so wiggle-test the harness while monitoring live data.
This code does not always mean the injector itself has failed; a faulty powertrain control module driver is possible but should only be suspected after all wiring and injector tests pass.

Can I keep driving with P2057?

You can usually drive the vehicle with this code, but the engine may enter limp mode or limit power, and continued driving can lead to increased emissions and potential damage to the SCR system. Avoid heavy loads and long distances until the fault is repaired, and do not ignore the warning light because it may trigger a derate condition.

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.