Technical Description of OBD-II Trouble Code
The exhaust aftertreatment fuel injector A is stuck closed.
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, etc. The repair steps may vary depending on the year, make, model, and powertrain configuration.
If your diesel-powered vehicle has stored a code P20D0, it means that the powertrain control module (PCM) has detected improper voltage outside the normal expected value range within the control circuit for the exhaust aftertreatment fuel injector A. The designation A indicates the use of multiple reductant injectors.
The exhaust aftertreatment system, also known as the selective catalyst reduction system, enhances the capabilities of the exhaust catalyst system. It may include items 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 to promote filtration and reduce harmful emissions.
The EAS and catalyst systems are monitored and controlled by the PCM or a stand-alone controller. The controller monitors various sensors to determine the appropriate time for DEF injection, ensuring optimal pollutant filtration.
If the PCM detects improper voltage in the control circuit for the EAS fuel injector, it will store a code P20D0 and may illuminate the malfunction indicator lamp.
What is the severity of this DTC?
A stored code P20D0 should be considered severe and addressed as quickly as possible, as it may damage the EAS system.
What are some of the symptoms of the code?
Symptoms of a P20D0 trouble code may include:
What are some of the common causes of the code?
Causes for this code may include:
What are some P20D0 troubleshooting steps?
To diagnose a code P20D0, you will need a diagnostic scanner, a digital volt/ohmmeter (DVOM), and vehicle-specific diagnostic information. It may also be helpful to refer to technical service bulletins (TSBs) that match your vehicle’s details.
Start by visually inspecting the EAS wiring harnesses and connectors for any damage. 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 enters readiness mode or the code is reset.
If the PCM enters readiness mode, the code is intermittent and may require worsening conditions for an accurate diagnosis. If the code is immediately reset, consult your vehicle information source for diagnostic flow charts, connector pin-out charts, and component testing procedures.
Use the DVOM to test the power supply to the EAS control system and test the fuses with the circuit loaded. If the power and ground circuits are functioning properly, use the scanner to activate the EAS fuel injector and test the output control circuit voltage. If the voltage is insufficient, suspect a faulty controller or programming error.
If the voltage output circuit is within parameters, use the DVOM to test the EAS fuel injector. If it fails to meet manufacturer’s specifications, it may be faulty.
