Technical Description of OBD-II Trouble Code
High Circuit for Reductant Injection Valve in Bank 1 Unit 2
What is the meaning of this?
This diagnostic trouble code (DTC) is a generic powertrain code that applies to many OBD-II vehicles (1996-newer). 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.
A stored code P2055 indicates that the powertrain control module (PCM) has detected excessive voltage in the control circuit for the reductant injection valve for engine bank one and selective catalyst reduction (SCR) system two. Bank 1 refers to the engine bank that contains the number one cylinder. Unit 2 indicates that multiple reductant injection or SCR systems are in use.
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 invented.
SCR systems inject a reductant compound or diesel exhaust fluid (DEF) into the exhaust in front of 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 perform 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 during extreme temperatures. These heaters are typically located in the DEF reservoir and/or the reductant injector supply hose(s).
If the PCM detects excessive voltage on the control circuit for the reductant injection valve for engine bank one unit two, a code P2055 will be stored and a malfunction indicator lamp may illuminate.
How severe is this DTC?
A stored code P2055 should be considered severe and addressed as quickly as possible. It could disable the SCR system. 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 P2055 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 P2055?
To diagnose a code P2055, you will need a diagnostic scanner, a digital volt/ohmmeter (DVOM), and vehicle-specific diagnostic information.
If you can find a technical service bulletin (TSB) that matches the vehicle’s year, make, and model, as well as the engine size, stored code/s, and exhibited symptoms, it could 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 code may be intermittent and 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 your diagnosis.
Use the DVOM to test the power supply to the SCR control system. Test 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 injector 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 fails to meet the manufacturer’s specifications, it is likely defective.
