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P2056 OBD-II Trouble Code: Reductant Injector Circuit/Open Bank 2 Unit 2

diagnostic check engine light

P2056 trouble code definition

The diagnostic trouble code P2056 indicates that the reductant injector that is located on bank 2 of the exhaust (system) has an open circuit.

Related Trouble Codes:

P2047 OBD-II Trouble Code: Reductant Injector Circ/Open Bank 1 Unit 1
P2048 OBD-II Trouble Code: Reductant Injector Circ/Low Bank 1 Unit 1
P2049 OBD-II Trouble Code: Reductant Injector Circ/High Bank 1 Unit 1
P2050 OBD-II Trouble Code: Reductant Injector Circ/Open Bank 2 Unit 1
P2051 OBD-II Trouble Code: Reductant Injector Circ/Low Bank 2 Unit 1
P2052 OBD-II Trouble Code: Reductant Injector Circ/High Bank 2 Unit 1
P2053 OBD-II Trouble Code: Reductant Injector Circ/Open Bank 1 Unit 2
P2054 OBD-II Trouble Code:Reductant Injector Circ/Low Bank 1 Unit 2
P2055 OBD-II Trouble Code: Reductant Injector Circ/High Bank 1 Unit 2
P2057 OBD-II Trouble Code: Reductant Injector Circ/Low Bank 2 Unit 2
P2058 OBD-II Trouble Code: Reductant Injector Circ/High Bank 2 Unit 2

What the P2056 code means

The reductant injector is a solenoid controlled by the powertrain control module (PCM). Diesel exhaust fluid (DEF) is given to the reductant injector by a pressure line and the injector sprays DEF into the exhaust system to help reduce pollutants that are in the exhaust.

The PCM uses information from the fuel injectors, throttle position (TP) sensor, mass airflow (MAF) sensor, coolant temperature sensor, and the manifold absolute pressure (MAP) sensor to activate the reductant injector. When the voltage for the reductant injector exceeds the specification that have been set by the manufacturer, the PCM stores the P2056 diagnostic trouble code.

What causes the P2056 code?

  • Defective reductant injector
  • Faulty reductant injector system controller
  • Melted wiring going to the reductant injector
  • Broken connector at the reductant injector
  • Exhaust leaks that are upstream from the reductant injector
  • Faulty coolant temperature sensor
  • Faulty throttle position sensor
  • Faulty manifold absolute pressure sensor
  • Faulty mass airflow sensor
  • Faulty powertrain control module

What are the symptoms of the P2056 code?

  • Check Engine Light is on
  • No symptoms at all
  • Black smoke coming from the exhaust pipe during acceleration

How does a mechanic diagnose the P2056 code?

  • Any diagnostic trouble codes stored by the PCM for the throttle position sensor, coolant temperature sensor, manifold absolute pressure sensor, or mass airflow sensor should be diagnosed and repaired before the diagnosis and repair of any reductant injector codes are completed. These sensors help the powertrain control module operate the reductant injector.

  • Inspect the wiring that leads to the reductant injector for wires that have melted, broken, or frayed.

  • Inspect the connector to the reductant injector for damage.

  • Use an OBD-II scanner to collect all diagnostic trouble codes that have been stored by the powertrain control module. This will assist in diagnosing any intermittent conditions. Also collect freeze frame data.

  • Inspect the exhaust for any large leaks that are upstream from the reductant injector.

  • Use a volt/ohmmeter to check the signal wire voltage. The signal wire should have a 5V reading.

  • If the signal wire does not have a 5V reading, the reductant injector will need to be replaced.

  • If the signal wire does have a 5V reading, check the PCM for continuity by comparing the signal wire continuity with the PCM continuity. If there is continuity, the PCM will need to be replaced or reprogrammed. It is rare for there to be a continuity issue with the PCM, but it is possible.

Common mistakes when diagnosing the P2056 code

  • Mistaking the oxygen sensor for the reductant injector. They are both located in the exhaust, in or near the catalyst converter, and they do look alike.

  • Overlooking any damaged wiring to the reductant injector

  • Not diagnosing throttle position sensor, coolant temperature sensor, mass airflow sensor, and/or manifold absolute pressure sensor diagnostic trouble codes, if stored, along with the P2056 diagnostic trouble code

How serious is the P2056 code?

The P2056 diagnostic trouble code has only one specific symptom of black smoke coming from the exhaust during acceleration. This black smoke will usually subside after acceleration. For this reason, the P2056 diagnostic trouble code is not one that is considered serious.

However, this code should be diagnosed and repaired before allowing an extended period of time to pass. Not doing so could potentially cause other issues or failures within the engine.

What repairs can fix the P2056 code?

Additional comments for consideration regarding the P2056 code

It is important to be sure that you are replacing the right component. Make sure that you know the difference between the reductant injector and the oxygen sensor as they look very similar. Replacing the reductant injector instead of the oxygen sensor, and vice versa, is a common mistake that is made. It is also important to note that this type of system is most commonly used in trucks that operate with diesel engines.

Need help with a P2056 code?

YourMechanic offers certified mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
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