Technical Description of OBD-II Trouble Code
Exhaust Gas Recirculation Sensor “A” Circuit Range/Performance
What does that signify?
This is a generic powertrain diagnostic trouble code (DTC) that applies to all makes and models from 1996 onwards. However, the specific troubleshooting steps may vary depending on the vehicle.
OBD trouble code P046C relates to a range or performance issue in the “A” electrical circuit to the exhaust gas recirculation (EGR) valve.
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. When temperatures exceed 2500 degrees F, Nitrates of Oxygen (Nox) are formed, 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. Consult a manufacturer-specific repair guide to determine which sensor corresponds to the “A” sensor in your particular vehicle.
EGR Operating Principles
The trouble code P046C refers to the same problem in all vehicles, but there are various types of EGRs, sensors, and activation methods. The only commonality 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.
Symptoms
The symptoms experienced 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 most 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.
