Technical Description of OBD-II Trouble Code
Performance Issue in Control Circuit for Exhaust Aftertreatment Fuel Injector A
What is the meaning of this?
This diagnostic trouble code (DTC) is a generic powertrain code that applies to many OBD-II vehicles (1996-newer), including vehicles from Mercedes Benz, Sprinter, GMC, Chevrolet, Ford, etc. Although it is a generic code, the specific repair steps may vary depending on the year, make, model, and powertrain configuration of the vehicle.
If your diesel-powered vehicle has stored a code P20CC, 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, designated as A. The designation A indicates the use of multiple reductant injectors.
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 consist of one or more 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 in front of 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 promotes the longevity 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 appropriate time for DEF (reductant) injection. DEF injection must be performed at the right moment and in precise measure to maintain an exhaust temperature within acceptable parameters and optimize pollutant filtration.
If the PCM detects improper voltage outside the normal expected value range within the control circuit for the EAS fuel injector, it will store a code P20CC and may illuminate a malfunction indicator lamp.
How severe is this DTC?
A stored code P20CC 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.
What are some of the symptoms of the code?
Symptoms of a P20CC trouble code may include:
What are some of the common causes of the code?
Possible causes for this code may include:
What are some troubleshooting steps for P20CC?
To diagnose a code P20CC, 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.
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 difficult to diagnose. In this case, 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 searching for vehicle information 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 power and ground circuits are found to be appropriate, 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 fails to meet the manufacturer’s specifications, it is likely defective.
