Technical Description of OBD-II Trouble Code
Intermittent/Erratic Circuit for Exhaust Gas Recirculation Sensor “B”
What does that signify?
This is a generic diagnostic trouble code (DTC) for the powertrain, which applies to all makes and models from 1996 onwards. However, the specific troubleshooting steps will vary depending on the vehicle.
OBD trouble code P046F refers to a problem in the electrical circuit “B” of the exhaust gas recirculation (EGR) valve, which is intermittent or erratic.
The purpose of the EGR valve 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 determine which sensor is the “B” sensor in your specific vehicle, refer to a manufacturer-specific repair guide.
EGR Operating Principles
The trouble code P046F 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 stall. Therefore, the computer programming only opens the EGR when the engine RPM is above 2000 and closes it when under a load.
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 how they regulate the opening of the pintle and sense 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 with excessive voltage can damage the computer’s sensor input terminal. Similarly, disconnecting the wrong connector can cause the computer to lose its programming, resulting in the vehicle failing to start until the dealer reprograms the computer.
If the common tests fail to resolve the problem, consult a service manual for further testing of the wiring circuits. The best solution is to take the vehicle to a service facility equipped with the appropriate diagnostic equipment, as they can quickly identify and repair this type of problem.
