Technical Description of OBD-II Trouble Code
The control circuit for the exhaust aftertreatment fuel injector B is experiencing low voltage.
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 P20D3, it means that the powertrain control module (PCM) has detected insufficient voltage in the control circuit for the exhaust aftertreatment fuel injector B. The designation B indicates that multiple reductant injectors are being used.
The exhaust aftertreatment system, also known as the selective catalyst reduction system, is used to enhance 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.
One of the functions of the exhaust aftertreatment system is to inject reductant compound/diesel exhaust fluid (DEF) into the exhaust before the diesel particulate filter, NOx trap, and/or the catalytic converter. This is done through an automated fluid storage and injection system. The introduction of DEF into the catalyst system helps prolong the life of the filtration element and reduces harmful exhaust emissions.
The PCM or a stand-alone controller monitors and controls the exhaust aftertreatment and catalyst systems. The controller uses input from sensors such as O2, NOx, and exhaust temperature sensors to determine the appropriate time for DEF injection. Proper DEF injection is crucial for maintaining an exhaust temperature within acceptable parameters and optimizing pollutant filtration.
If the PCM detects insufficient voltage in the control circuit for the exhaust aftertreatment fuel injector, it will store a code P20D3 and may illuminate the malfunction indicator lamp.
What is the severity of this DTC?
A stored code P20D3 should be considered severe and addressed as quickly as possible. The conditions that led to the code being stored may have caused damage to the exhaust aftertreatment system.
What are some of the symptoms of the code?
Symptoms of a P20D3 trouble code may include:
What are some of the common causes of the code?
Possible causes for this code include:
What are some P20D3 troubleshooting steps?
To diagnose a code P20D3, 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 wiring harnesses and connectors of the exhaust aftertreatment system. 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 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 difficult 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 exhaust aftertreatment fuel injector A.
Use the DVOM to test the power supply to the exhaust aftertreatment control system by measuring voltage drop. Test the fuses with the circuit loaded to avoid misdiagnosis. If the power and ground circuits are functioning properly, use the scanner to activate the exhaust aftertreatment fuel injector (solenoid) and test the output control circuit voltage. If the voltage is insufficient, suspect a faulty controller or a programming error.
If the voltage output circuit is within parameters, use the DVOM to test the exhaust aftertreatment fuel injector in question. If the injector does not meet the manufacturer’s specifications, it may be faulty.
