Technical Description of OBD-II Trouble Code
Performance Issue in the Control Circuit of Exhaust Aftertreatment Fuel Injector B
What does that signify?
This diagnostic trouble code (DTC) is a generic powertrain code that is applicable to many OBD-II vehicles (1996-newer). This includes vehicles from Mercedes Benz, Sprinter, GMC, Chevrolet, Ford, and others. While it is a generic code, the specific repair steps may vary depending on the year, make, model, and powertrain configuration.
If your diesel-powered vehicle has stored a code P20D2, it means that the powertrain control module (PCM) has detected abnormal voltage outside the expected range within the control circuit for the exhaust aftertreatment fuel injector, designated as B. The designation B indicates the use of multiple reductant injectors.
The exhaust aftertreatment system, also known as the selective catalyst reduction system, is utilized to enhance the capabilities of the exhaust catalyst system. It may consist of various 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 before the diesel particulate filter, NOx trap, and/or the catalytic converter. This is done through an automated fluid storage and injection system. Introducing DEF into the catalyst system helps prolong the lifespan of the filtration element and reduces the release of harmful exhaust emissions 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 such as O2, NOx, and exhaust temperature sensors, among others, to determine the appropriate timing for DEF (reductant) injection. DEF injection must be performed at the precise moment and in the correct amount to maintain an exhaust temperature within acceptable parameters and optimize pollutant filtration.
If the PCM detects abnormal voltage outside the expected range within the control circuit for the EAS fuel injector, a code P20D2 will be stored and a malfunction indicator lamp may illuminate.
What is the severity of this DTC?
A stored code P20D2 should be considered severe and addressed as quickly as possible. The EAS system may be damaged as a result of the conditions that led to the storage of the code P20D2.
What are some of the symptoms of the code?
Symptoms of a P20D2 trouble code may include:
What are some of the common causes of the code?
Possible causes for this code may include:
What are some P20D2 troubleshooting steps?
To diagnose a code P20D2, 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 the vehicle’s year, make, and model, as well as the engine size, stored code/s, and exhibited symptoms. This can provide valuable diagnostic information.
I recommend starting the diagnosis with a visual inspection of the EAS wiring harnesses and connectors. If any burnt or damaged wiring or connectors are found, they should be repaired or replaced before proceeding.
Next, connect the scanner to the vehicle diagnostic connector and retrieve all stored codes and relevant freeze frame data. It is advisable to write 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 at this point, the code is intermittent and may be more challenging to diagnose. In such cases, the conditions that led to the storage of the code may need to worsen before an accurate diagnosis can be made.
If the code is immediately reset, the next step of the diagnosis will require referring to the vehicle information source to obtain diagnostic flow charts, connector pin-out charts, connector face views, as well as component testing procedures and specifications. The vehicle information source can also help pinpoint the exact location of EAS fuel injector A.
Use the DVOM to test (voltage drop) the power supply to the EAS control system. Test fuses with the circuit loaded to avoid misdiagnosis. If the appropriate power (battery voltage) and ground circuits are identified, 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 incorrectly programmed controller.
If the voltage output circuit is within the specified parameters, use the DVOM to test the EAS fuel injector in question. If the injector fails to meet the manufacturer’s specifications, it is likely defective.
