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Error Code P046F is defined as Exhaust Gas Recirculation Sensor B Circuit Intermittent.
This code is a generic trouble code, meaning it applies to all vehicles equipped with OBD-II, especially those made since 1996 up to present. Specifications on the definition, troubleshooting and repairs, of course, vary from one make and model to another.
The job of the EGR valve is to introduce a regulated level of exhaust gas into the intake manifold to maintain the cylinder head temperature of 2500˚ F. NOx (oxides of Nitrogen) are formed when the temperature goes over 2500˚ F, and NOx is responsible for atmospheric pollution and smog.
Error Code P046F is detected when the PCM (powertrain control module, or ECM engine control module in other vehicle makes) detects an abnormally low, high, or non-existent signal voltage.
Error Code P046F is a similar problem to all vehicles. But since there are many types of EGRs, sensors, and methods of activation, the only similarity is that they all vent exhaust gas to the intake manifold to cool the cylinder head temperatures.
Presenting consumed exhaust gas into the engine at the wrong time reduces horsepower, causing the vehicle to idle rough or stall. Thus, computer programming only opens the EGR when the RPM goes over 2000 and closes when under a load.
As with other error codes, this code activates the Check Engine light and registers the code to the vehicle’s system. Other symptoms depend on the EGR’s pintle position when the failure occurred.
- Second code related to EGR sensor failure may be set. Error Code P044C relates to low sensor voltage, while Error Code P044D means high voltage condition
- EGR pintle stuck partly open making the vehicle unable to idle properly or stall
- Pinging sound from detonation when vehicle is under a load or at high RPM
In some cases, there can be no symptoms at all.
There are different factors that can lead to this code, such as:
- Faulty EGR sensor “B”
- Faulty wiring harness to the sensor
- Carbon buildup causing the EGR pintle to be stuck in closed position
- Lack of vacuum to the EGR solenoid
- Faulty EGR solenoid
- Faulty EGR position sensor
- Faulty differential pressure feedback EGR sensor
How to Check
In diagnosing this code, keep in mind that the wiring differs from one manufacturer to another, and computers may not react well if the wrong wire is probed. Probing the wring wire will send excessive voltage through the computer’s sensor input terminal, and may fry the computer.
Also, if the wrong connector is disconnected, the computer could lose all of its programming, causing the vehicle to fail to start again. If this happens, the vehicle must be taken to the dealer to reprogram the computer.
To start the diagnosis, technicians usually check the EGR sensor connector first and look for signs of corrosion, bent, or pushed out terminals, and loose connections. Then they clean off any corrosion and re-seat the connector.
Next, they proceed on removing the electrical connector and the EGR. Then they check for coking in the EGR intake and exhaust. They clean out any coking present to allow the pintle to move up and down smoothly.
Then they check the vacuum line from the EGR to the solenoid, look for any defects and damages and replace it if there are any damages found.
Next, they check the solenoid electrical connector and look for signs of corrosion and damages.
For Ford vehicles, technicians will have to follow the two vacuum hoses from the EGR to the DPFE (Differential Pressure Feedback EGR) sensor in the rear of the manifold.
Next, they check the two pressure hoses and look for signs of corrosion. These hoses usually clog carbon from the exhaust. Thus, technicians will use a small pocket screwdriver or equivalent to clean the hoses from corrosion, and the sensor will start running again.
How to Fix
Common repairs include:
- Remove and clean off corrosion from the EGR sensor connector
- Remove coking in the EGR intake and exhaust
- Replacement of damaged EGR vacuum lines to the solenoid
- Cleaning of vacuum hoses of the EGR to the DPFE sensor
- Unclogging of vacuum hoses from carbon buildup
Failure in the wiring harness and sensor is the most common cause for this code, so it’s important to refer to the service manual of the vehicle to determine the proper wire identification and diagnostics procedure of this error code.
If the common test fails to solve the problem, a service manual is needed to test the wiring circuits. In such case, the best solution for this is to take the vehicle to a service facility with the right diagnostic equipment. Professional technicians can identify and repair this problem quickly.