Technical Description of OBD-II Trouble Code
Open Circuit or Failure of Reductant Injection Valve in Bank 2 Unit 2
What is the meaning of this code?
This diagnostic trouble code (DTC) is a generic powertrain code that is applicable to various OBD-II vehicles manufactured from 1996 onwards. This includes vehicles from Ford, Mercedes Benz, Sprinter, Smart, Ram, and others. While it is a generic code, the specific repair steps may vary depending on the year, make, model, and powertrain configuration of the vehicle.
A stored code P2056 indicates that the powertrain control module (PCM) has detected no voltage in the control circuit for the reductant injection valve in engine bank two and selective catalyst reduction (SCR) system two. Bank 2 refers to the bank of the engine that does not contain the number one cylinder. Unit 2 indicates that multiple reductant injection or SCR systems are being used.
The catalyst system is responsible for reducing almost all exhaust emissions, although certain applications also have a NOx trap.
Exhaust gas recirculation (EGR) systems go a step further in reducing NOx. However, larger and more powerful diesel engines today cannot meet strict federal (U.S.) emission standards with just the EGR, diesel particulate filter/catalytic converter, and NOx trap. This is why selective catalytic reduction (SCR) systems were developed.
SCR systems inject a reductant compound or diesel exhaust fluid (DEF) into the exhaust before the diesel particulate filter, NOx trap, and/or the catalytic converter using the reductant injection valve (solenoid). The precisely timed DEF injection raises the temperature of the filtration element, allowing it to function more efficiently. This enhances the longevity of the filtration element and reduces the release of harmful exhaust emissions into the atmosphere.
The entire SCR system is monitored and controlled by either the PCM or a stand-alone controller that interacts with the PCM. The controller monitors the O2, NOx, and exhaust temperature sensors, among other inputs, to determine the appropriate time for DEF (reductant) injection. Precise DEF injection is necessary to maintain exhaust temperature within acceptable parameters and optimize pollutant filtration.
Reductant heaters are used to prevent diesel exhaust fluid from freezing in extreme temperatures. These heaters are typically located in the DEF reservoir and/or the reductant injector supply hose(s).
If the PCM detects no voltage on the control circuit for the reductant injection valve in engine bank two unit two, a code P2056 will be stored and a malfunction indicator lamp may illuminate.
How severe is this DTC?
A stored code P2056 should be considered severe and addressed as soon as possible. It could disable the SCR system, and failure to rectify the conditions that led to the code being stored in a timely manner could result in catalyst damage.
What are some of the symptoms of the code?
Symptoms of a P2056 trouble code may include:
What are some of the common causes of the code?
Possible causes for this code may include:
What are some troubleshooting steps for P2056?
To diagnose a code P2056, you will need a diagnostic scanner, a digital volt/ohmmeter (DVOM), and access to vehicle-specific diagnostic information.
If you can find a technical service bulletin (TSB) that matches the year, make, and model of the vehicle, as well as the stored code/s and exhibited symptoms, it can provide helpful diagnostic information.
Start the diagnosis by visually inspecting the reductant heater system harnesses and connectors. Repair or replace any burnt or damaged wiring and connectors before proceeding.
Next, connect the scanner to the vehicle diagnostic connector and retrieve all stored codes and relevant freeze frame data. Write down this information before clearing the codes and test driving the vehicle until the PCM either enters readiness mode or the code is reset.
If the PCM enters readiness mode, the intermittent nature of the code may make it more difficult to diagnose at this time. In such cases, the conditions that led to the code being stored may need to worsen before an accurate diagnosis can be made.
If the code is reset, consult your source of vehicle information to obtain diagnostic flow charts, connector pinout charts, connector face views, as well as component testing procedures and specifications. This information will be necessary to complete the next step of the diagnosis.
Use the DVOM to test the power supply to the SCR control system. Test the fuses with the circuit loaded to avoid misdiagnosis. If the appropriate power (battery voltage) and ground circuits are present, use the scanner to activate the reductant injection valve (solenoid) and test the output control circuit voltage. If the voltage is insufficient, suspect a faulty or incorrectly programmed controller.
If the voltage output circuit is within parameters, use the DVOM to test the reductant injection valve in question. If the valve does not meet the manufacturer’s specifications, it is likely to have failed.
