Technical Description of OBD-II Trouble Code
The exhaust aftertreatment fuel injector B 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 exact repair steps may vary depending on the year, make, model, and powertrain configuration.
If your diesel-powered vehicle has stored a code P20D6, 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 B. The designation B indicates that multiple reductant injectors are in use.
The exhaust aftertreatment system, also known as the selective catalyst reduction system, enhances the capabilities of the exhaust catalyst system. It may consist of items such as a diesel oxidation catalyst, diesel particulate filter, reductant injection system, ammonia slip catalyst, and a nitrogen oxide (NOx) trap.
Among other things, the exhaust aftertreatment systems are responsible for injecting reductant compound/diesel exhaust fluid (DEF) into the exhaust in front of the diesel particulate filter, NOx trap, and/or the catalytic converter via an automated fluid storage and injection system. This helps promote filtration element longevity and reduces harmful exhaust emissions.
The EAS and catalyst systems are monitored and controlled by either the PCM or a stand-alone controller. The controller monitors various sensors, including O2, NOx, and exhaust temperature sensors, to determine the appropriate time for DEF injection. Proper DEF injection is crucial for maintaining an acceptable exhaust temperature and optimizing pollutant filtration.
If the PCM detects improper voltage outside the normal expected value range within the control circuit for the EAS fuel injector, a code P20D6 will be stored and a malfunction indicator lamp may illuminate.
What is the severity of this DTC?
A stored code P20D6 should be considered severe and addressed as quickly as possible. The EAS system may be damaged as a result of the conditions that contributed to the code being stored.
What are some of the symptoms of the code?
Symptoms of a P20D6 trouble code may include:
What are some of the common causes of the code?
Possible causes for this code may include:
What are some P20D6 troubleshooting steps?
To diagnose a code P20D6, you will need a diagnostic scanner, a digital volt/ohmmeter (DVOM), and vehicle-specific diagnostic information.
Start by locating a technical service bulletin (TSB) that matches the vehicle’s year, make, and model, as well as the engine size, stored codes, and exhibited symptoms. This information can provide helpful diagnostic guidance.
Begin the diagnosis with a visual inspection of 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 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 contributed to the code being stored may need to worsen before an accurate diagnosis can be made.
If the code is immediately reset, 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 (voltage drop). Test fuses with the circuit loaded to avoid misdiagnosis. If the power and ground circuits are correct, use the scanner to activate the EAS fuel injector (solenoid) and test the output control circuit voltage. Insufficient voltage may indicate a faulty controller or programming error.
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 may be faulty.
