Exhaust Gas Recirculation A Control Position Exceeded Learning Limit
What does this mean?
This is a generic diagnostic trouble code (DTC) for the powertrain that generally applies to OBD-II equipped vehicles with an Exhaust Gas Recirculation (EGR) system. This may include, but is not limited to, vehicles from Dodge/Ram (Cummins), Chevy/GMC (Duramax), Honda, Jeep, Hyundai, etc.
Although generic, the exact repair steps may vary depending on the year, make, model, and powertrain configuration.
If your OBD-II equipped vehicle has stored a P049D code, it means the Powertrain Control Module (PCM) has detected a malfunction in a certain control position of the exhaust gas recirculation (EGR) valve. It referred to a specific position of the EGR valve.
The EGR valve system is designed to recirculate a portion of the spent exhaust gases back to the intake manifold, in measured increments, so it can be burned a second time. This process is essential in reducing nitrogen oxide (NOx) particles that are released into the atmosphere as a byproduct of internal combustion and diesel engine operation. NOx is suspected to be a contributing factor to the depletion of the ozone layer from exhaust emissions. NOx emissions are regulated by federal mandate in North American vehicles.
The learning limit is a programmed degree that reflects the minimum and maximum parameters to which a certain position (A) of the EGR valve can adapt. If the PCM detects that the actual EGR valve position is beyond these parameters, a P049D code will be stored and a Malfunction Indicator Lamp (MIL) may be illuminated. In some vehicle applications, multiple ignition cycles (with a fault) are required for the MIL to illuminate.
How severe is this DTC?
Since the P049D code pertains to the EGR system, it should not be considered severe.
What are some of the symptoms of the code?
Symptoms of a P049D fault code may include:
There will likely be no symptoms associated with this code
Slightly decreased fuel efficiency
Possible drivability issues
What are some of the common causes of the code?
Causes
of this P049D code may include:
Faulty EGR valve
Faulty EGR sensor
Incorrect PCM or PCM programming error
What are the troubleshooting steps for P049D?
I would typically begin my diagnosis by locating the vehicle’s diagnostic connector and retrieving all stored codes and associated data. I would write down all this information in case I need it as I proceed with my diagnosis. Then, I would test the vehicle to see if the code immediately resets.
By searching the vehicle’s Technical Service Bulletins (TSBs) for entries that match the vehicle, stored codes, and displayed symptoms, you may discover the solution to your (potentially difficult) diagnosis. Since TSB entries come from thousands of repair specialists, they often contain very helpful details.
If P049D is stored after clearing the codes, I would have access to a diagnostic scanner, a digital volt/ohmmeter (DVOM), and a reliable source of vehicle information.
Now, I would perform a visual inspection of the EGR valve and all associated wiring and connectors. Focus on wiring harnesses that are routed near hot exhaust components and the sharp edges often associated with heat shields.
NOTE: Disconnect all associated controllers from the circuit before testing resistance/continuity with the DVOM.
Using wiring diagrams and connector pinout charts, located in your vehicle information source, test each EGR valve connector circuit (with the DVOM) for the proper signal. It may be necessary to manually activate the EGR system using the scanner, as most systems require a defined vehicle speed before automatic activation can occur. Circuits that do not meet manufacturer specifications will need to be traced back to the source (usually the PCM connector) and retested. If the PCM output signal is not detected, suspect a PCM programming error or faulty PCM. Otherwise, repair or replace open/short-circuited circuits as needed.
Use the DVOM to test the actual EGR valve and integrated sensors if all circuits meet manufacturer specifications. Your vehicle information source will again provide information for testing this component. If the EGR valve and all (integrated) sensors do not align with manufacturer specifications, suspect it is faulty.
This code should only be displayed in vehicles equipped with an EGR valve.