Technical Description of OBD-II Trouble Code
Range/Performance Issue with Reductant Injection Valve Circuit for Bank 2 Unit 1
What does that signify?
This diagnostic trouble code (DTC) is a generic powertrain code that is applicable to various 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 P201A indicates that the powertrain control module (PCM) has detected abnormal voltage in the control circuit for the reductant injection valve for engine bank two and selective catalyst reduction (SCR) system one. Bank 2 refers to the bank of the engine that does NOT contain the #1 cylinder.
The catalyst system is responsible for reducing (essentially) all exhaust emissions, although certain applications may 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 via 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 crucial for maintaining exhaust temperature within acceptable parameters and optimizing 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 voltage on the control circuit for the reductant injection valve that is outside the normal range or performance parameters for engine bank 2 unit one, a code P201A will be stored and a malfunction indicator lamp may illuminate.
What is the severity of this DTC?
A stored code P201A 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 P201A trouble code may include:
What are some of the common causes of the code?
Possible causes for this code may include:
What are some P201A troubleshooting steps?
To diagnose a code P201A, 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.
Begin 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, diagnosing the code may be more difficult at this time since it is intermittent. 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 injector valve (solenoid) and test the output control circuit voltage. If the voltage is insufficient, suspect a faulty or improperly 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.
