P046C Exhaust Gas Recirculation Sensor Range

OBD-II Trouble Code - P046C - Datasheet

P046C - Exhaust Gas Recirculation Sensor "A" Circuit Range/Performance

What does DTC P046C mean?

This is a Generic Transmission Diagnostic Trouble Code (DTC), which means it applies to all makes / models from 1996 onwards. However, specific troubleshooting steps may differ from vehicle to vehicle.

An on-board diagnostic (OBD) trouble code P046C is a generic trouble code relating to a range or performance issue that has occurred in the Exhaust Gas Recirculation (EGR) valve circuit "A".

The exhaust gas recirculation valve is used to supply a controlled amount of exhaust gas to the intake manifold. The goal is to keep the cylinder head temperature below 2500 degrees Fahrenheit. Oxygen nitrates (Nox) are formed when temperatures rise above 2500 degrees Fahrenheit. Nox is responsible for smog and air pollution.

The control computer, either the powertrain control module (PCM), or the electronic control module (ECM) has detected an abnormally low, high, or nonexistent signal voltage. Refer to the manufacturer's repair manual to determine which sensor “A” is installed in your specific vehicle.

How the exhaust gas recirculation works

DTC P046C refers to the same problem on all vehicles, however there are many types of EGR, sensors and activation methods. The only similarity is that they all release exhaust gases into the intake manifold to cool the cylinder head.

Pouring exhaust gas into the engine at the wrong time lowers horsepower and causes it to idle or stall. With this in mind, computer programming only opens EGR at engine rpm above 2000 and closes under load.

Symptoms

As with other error codes, this code activates the Check Engine light and logs the code into the vehicle's system. Other symptoms depend on the position of the EGR pin at the time of the malfunction.

Symptoms depend on the position of the exhaust gas recirculation needle at the time of the fault.

• A second code related to EGR sensor failure may be set. Error code P044C refers to low sensor voltage, while error code P044D refers to a high voltage condition.
• The EGR pin is partially open, causing the vehicle to not idle properly or stall
• Detonation sound when the car is under load or at high speeds
• Soon the service engine light will come on and the OBD code P046C will be set. Optionally, a second code may be set related to EGR sensor failure. P044C refers to a low sensor voltage and P044D refers to a high voltage situation.
• If the EGR pin is partially stuck open, the vehicle will not idle or stall.
• Knock ringing can be heard under load or at high rpm
• No symptoms

Possible Causes of Code P046C

• Defective exhaust gas recirculation sensor "A"
• Defective wiring harness to the sensor
• The EGR pin is stuck in the closed position and carbon build-up is preventing it from opening
• Lack of vacuum at the exhaust gas recirculation solenoid.
• Faulty exhaust gas recirculation solenoid
• Exhaust gas recirculation position sensor defective
• The differential pressure feedback sensor of the exhaust gas recirculation system is defective.

How to Check DTC P046C

When diagnosing this code, be aware that wiring differs from one manufacturer to another, and computers may not respond well if the wrong wire is being probed. Contact with the crimp wire will cause excess voltage to flow through the computer's sensor input connector, which may cause the computer to burn.

Also, if the wrong connector is disconnected, the computer may lose all of its programs, making it impossible to start the car. In this case, the car must be taken to the dealer to have the computer reprogrammed.

To begin a diagnosis, technicians usually first check the EGR sensor connector and look for signs of corrosion, bent or extended terminals, and loose connections. They then clean off the corrosion and reseat the connector.

Then they proceed to remove the electrical connector and the EGR. Then check for coking intake and exhaust system EGR. They remove any carbon deposits present so that the pin moves up and down smoothly.

Then they check the vacuum line from the EGR to the solenoid, look for defects and damage and replace it if damage is found.

They then check the solenoid electrical connector and look for signs of corrosion and damage.

For Ford vehicles, technicians will have to follow two vacuum hoses from the EGR to a DPFE (EGR Differential Pressure Feedback) sensor at the rear of the manifold.

Then they check two pressure hoses and look for signs of corrosion. These hoses usually clog exhaust gases. So the technicians will use a small pocket screwdriver or similar tool to remove the corrosion from the hoses and the sensor will start working again.

Repair procedures

All EGR valves have one thing in common - they recirculate exhaust gases from the exhaust system to the intake manifold. In addition, they differ in the methods of regulating the opening of the needle and determining its position.

The following repair procedures are the most common problems that account for most EGR failures. If the wiring harness or sensor fails, a service manual is required to determine the correct wire identification and diagnostic procedures.

Be aware that wiring varies from manufacturer to manufacturer, and computers do not respond well if the wrong wire is probed. If you examine the wrong wire and send excessive voltage across the computer's sensor input terminal, the computer will start to burn.

At the same time, if the wrong connector is disconnected, the computer may lose programming, making it impossible to start the engine until the dealer reprograms the computer.

• P046C indicates a problem on circuit B, so check the EGR sensor connector for corrosion, bent or extruded terminals, or a loose connection. Remove the rust and reinstall the connector.
• Disconnect the electrical connector and remove the exhaust gas recirculation system. Check the exhaust gas recirculation inlet and outlet for coke. If necessary, clean of coke so that the needle moves smoothly up and down.
• Check the vacuum line from the exhaust gas recirculation system to the solenoid and replace it if any defects are found.
• Check the solenoid electrical connector for corrosion or defects.
• If the vehicle is a Ford, follow the two vacuum hoses from the exhaust gas recirculation system to the differential pressure feedback exhaust gas recirculation (DPFE) sensor at the rear of the manifold.
• Check the two pressure hoses for corrosion. Experience has shown that these hoses drown out carbon deposits from the exhaust pipe. Use a small pocket screwdriver or similar to remove any corrosion from the hoses and the sensor will start working again.

If the most common tests do not solve the problem, a service manual is needed to continue checking the electrical circuits. The best solution is to take the car to a service center with the appropriate diagnostic equipment. They can quickly identify and fix this type of problem.

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