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    P2056 Reductant Injection Valve Circuit/Open Bank 2 Unit 2

    What does this OBD II code mean? 

    This generic OBD2 code is set when the Powertrain Control Module (PCM) detects an open circuit in the reductant injection valve.
    This particular code is pointing out the bank 2, in other words, the bank of cylinders not containing cylinder #1. The unit 2 tag is indicating that more than one injector is used for the bank 2.

    Why does this OBD II code appear?

    On modern diesel engines, the use of an Exhaust Recirculation Valve (EGR) is not enough to fully control the amount of NOx present in the exhaust gases. That’s why the use of reductant injection systems is necessary. This system consists of one or more injectors (solenoids) commanded by the PCM that sprays a diesel exhaust fluid (DEF) just before the diesel particulate filter which in turn is part of the Selective Catalyst Reduction (SCR) system. The fluid elevates the temperature of the filter element increasing its efficiency and longevity. The injection valve solenoid only operates under certain conditions though. It’s the job of the PCM/SCR module activating this solenoid after analyzing the information from its sensors and hence helping to transform the harmful NOx emissions to nitrogen, carbon dioxide, and water.
    The OBD2 code P2056 is stored in memory when the PCM detects an open circuit in the solenoid valve (no voltage).

    What symptoms may occur with this OBD II code?

    Expect the typical symptoms from a P2056 condition:

    • CEL lit. The Check Engine Light will turn on after few driving cycles to alert the driver about the situation. 
    • Possible decrease in fuel economy.
    • Black smoke coming from the tailpipe due to NOx leftovers.

    What are the causes that trigger this OBD II code?

    There're many factors that could cause a P2056 condition including among others the following:

    • Damaged, burnt, corroded, open or shorted injector valve wiring. 
    • Worn, corroded, burnt, disconnected or bent wiring harness connector pins. 
    • Faulty or deficient DEF injector valve solenoid.
    • Even when unlikely, a defective PCM cannot be discarded.

    Please notice that possible causes are based on the assumption that only trouble code P2056 is stored in memory.

    Diagnostic strategy for troubleshooting this OBD II code

    Warning: If any other code directly related with temperature, vacuum or throttle position sensor is present then you must start diagnosing and solving those codes first.

    It's highly recommended starting the diagnostic process with the usual information gathering:

    • With the help of a professional OBD2 scan tool, preferably one with OEM capabilities, take note of all data trouble codes in memory, including pending codes.
    • Take note of freeze frame information (if present).
    • Query the vehicle owner about what, when and where the failure occurs. Does it happen with the engine hot? Cold? Under load? All the standard questions.
    • Take note of the vehicle VIN and find a reliable source of technical reference.

    Once you are done, the next step is discarding an intermittent condition. 

    • Using your scan tool clear DTC memory. 
    • Perform a complete driving cycle according to OEM procedures.

    If the code P2056 disappears then inform the owner about the intermittent nature of the code and explain that further testing with the code present will be required. If the code does appear then continue to the testing stage, consisting in discarding the possible causes of the problem. 

    IMPORTANT: the diagnostic procedure explained in this section should be taken as a guideline. Always refer to specific OEM procedures when possible.

    The workflow for the diagnostic process is:

    • The tests should be executed in sequential order, in other words, complete step 1 before going to step 2 and so on.
    • Repair, fix, or replace any component if you suspect is not in good condition.
    • If any repair, fix, reprogramming or component replacement is made during any step then you should clear DTC memory and repeat the whole KOER driving cycle.
    • If the DTC appear again then you should continue to the next step.
    • If the DTC does not appear again after completing the KOER tests then you can assume the problem is fixed, in that case, continuing with the remaining steps would be optional.

    The diagnostic process for the code P2056 is as follows:

    1. Sensor harness wiring and connector: carry out an exhaustive visual inspection of bank 2 DEF solenoid wiring and connectors. Pay special attention to burnt, corroded, open, shorted to ground or deteriorated wiring and/or connector. Unplug the solenoid and check for corrosion, damage, bent pins, etc.
    2. Electrical tests: with the help of a digital volt-ohm meter (DVOM) and the adequate wiring diagram perform a KOEO check on the DEF solenoid. Verify supply and/or reference voltage, electrical resistance, continuity, current and ground integrity. Compare the obtained values with the appropriate OEM literature.
    3. Problems with the powertrain control module: the most unlikely cause for this code is a faulty PCM or SCR module. Yet, if you are completely certain that all prior tests passed then you must remove the PCM/SCR module and check it, reprogram it or replace it as necessary.
       

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