Technical Description of OBD-II Trouble Code
The control circuit for the exhaust aftertreatment fuel injector B is open or experiencing a circuit malfunction.
What does that mean?
This diagnostic trouble code (DTC) is a generic powertrain code that applies to many OBD-II vehicles (1996-newer), including Mercedes Benz, Sprinter, GMC, Chevrolet, Ford, and others. The specific repair steps may vary depending on the year, make, model, and powertrain configuration.
If your diesel-powered vehicle has a stored code P20D1, it means that the powertrain control module (PCM) has detected no voltage in the control circuit for the exhaust aftertreatment fuel injector B. The designation B indicates that multiple reductant injectors are in use.
The exhaust aftertreatment system, also known as the selective catalyst reduction system, is used to improve the capabilities of the exhaust catalyst system. It may include components such as the diesel oxidation catalyst, diesel particulate filter, reductant injection system, ammonia slip catalyst, and a nitrogen oxide (NOx) trap.
Among other functions, the exhaust aftertreatment systems (EAS) are responsible for injecting reductant compound/diesel exhaust fluid (DEF) into the exhaust system before the diesel particulate filter, NOx trap, and/or catalytic converter. This helps prolong the lifespan of the filtration element and reduces harmful exhaust emissions released into the atmosphere.
The EAS and catalyst systems are monitored and controlled by either the PCM or a stand-alone controller that interacts with the PCM. The controller monitors various sensors, including O2, NOx, and exhaust temperature sensors, to determine the optimal time for DEF injection. Proper DEF injection is crucial to maintain an acceptable exhaust temperature and optimize pollutant filtration.
If the PCM detects no voltage on the control circuit for the EAS fuel injector, it will store a code P20D1 and may illuminate the malfunction indicator lamp.
What is the severity of this DTC?
A stored code P20D1 should be considered severe and addressed as quickly as possible. The EAS system may be damaged due to the conditions that led to the code being stored.
What are some of the symptoms of the code?
Symptoms of a P20D1 trouble code may include:
What are some of the common causes of the code?
Possible causes for this code may include:
What are some P20D1 troubleshooting steps?
To diagnose a code P20D1, you will need a diagnostic scanner, a digital volt/ohmmeter (DVOM), and access to vehicle-specific diagnostic information.
It may be helpful to find a technical service bulletin (TSB) that matches your vehicle’s year, make, and model, as well as the engine size, stored codes, and exhibited symptoms.
Start the diagnosis by visually inspecting the EAS wiring 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. Consider writing down this information before clearing the codes. Test drive the vehicle until the PCM either enters readiness mode or the code is reset.
If the PCM enters readiness mode, the code is intermittent and may be more challenging to diagnose. In this case, the conditions that led to the code being stored may need to worsen before an accurate diagnosis can be made.
If the code is immediately reset, you will need to consult your vehicle information source to obtain diagnostic flow charts, connector pin-out charts, connector face views, and component testing procedures and specifications. You can also use the information source to locate the exact position of EAS fuel injector A.
Use the DVOM to test the power supply to the EAS control system by measuring voltage drop. Test the fuses with the circuit loaded to avoid misdiagnosis. If the power and ground circuits are functioning correctly, use the scanner to activate the EAS fuel injector (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 EAS fuel injector in question. If the injector does not meet the manufacturer’s specifications, it is likely defective.
