Technical Description of OBD-II Trouble Code
Range/Performance Issue with Exhaust Gas Recirculation Sensor “C”
What does that signify?
This is a generic diagnostic trouble code (DTC) for powertrain issues, applicable to all makes and models from 1996 onwards. However, the troubleshooting steps may vary depending on the vehicle.
OBD trouble code P044B indicates a range or performance problem in the electrical circuit “C” of the exhaust gas recirculation (EGR) valve.
The EGR valve’s purpose is to introduce a regulated amount of exhaust gas into the intake manifold in order to maintain cylinder head temperatures below 2500 degrees F. This is important because temperatures above 2500 degrees F lead to the formation of Nitrates of Oxygen (Nox), which contribute to smog and atmospheric pollution.
The controlling computer, either the powertrain control module (PCM) or the electronic control module (ECM), has detected an abnormally low, high, or non-existent signal voltage. To identify the “C” sensor in your specific vehicle, refer to the manufacturer’s repair guide.
EGR Operating Principles
The trouble code P044B refers to the same problem in all vehicles, but there are various types of EGRs, sensors, and activation methods. The common factor is that they all release exhaust gas into the intake manifold to cool the cylinder head temperatures.
Introducing spent exhaust gas into the engine at the wrong time reduces horsepower and can cause a rough idle or stalling. Therefore, the computer programming only opens the EGR when the engine RPM is above 2000 and closes it when under a load.
Related EGR sensor “C” trouble codes:
Symptoms
The symptoms depend on the position of the EGR pintle at the time of failure.
Potential Causes
Repair Procedures
All EGR valves have one thing in common – they recirculate exhaust from the exhaust to the intake manifold. However, they differ in their methods for regulating the opening of the pintle and sensing its position.
The following repair procedures address the most common problems that account for the majority of failures in the EGR system. Wiring harness or sensor failures require a service manual to determine the proper wire identification and diagnostic procedures.
It is important to note that the wiring varies between manufacturers, and probing the wrong wire can cause damage to the computer. Similarly, disconnecting the wrong connector can result in the loss of programming in the computer, requiring reprogramming by a dealer to start the vehicle again.
If the common tests fail to solve the problem, a service manual is required to continue testing the wiring circuits. The best solution is to take the vehicle to a service facility with the appropriate diagnostic equipment. They can quickly identify and repair this type of problem.
