Fault code P049C – exhaust gas recirculation “B” flow excessive detected

Fault code P049C is called “Exhaust Gas Recirculation (EGR) “B” Flow Excessive Detected” but in different programs it may be called differently. This fault designation applies to all vehicles equipped with OBD-II.

Technical description and explained code P049C

This Diagnostic Trouble Code (DTC) is a generic powertrain code. The P049C error is considered a generic code because it applies to all makes and models of vehicles. Although the specific repair steps may vary slightly from model to model.

Fault code P049C – exhaust gas recirculation

EGR is responsible for exhaust gas recirculation. It is part of the vehicle’s exhaust emission system. It is used to reduce temperature, combustion pressure, and to control nitrogen oxides.

Typically, an exhaust gas recirculation system consists of three parts:

  • The exhaust gas recirculation valve.
  • Solenoid actuator.
  • An exhaust gas recirculation differential pressure sensor (DPFE).

They work together to provide the correct amount of recirculation depending on engine temperature, load, etc.

Code P049C means that the OBD has detected excessive exhaust gas flow in the intake manifold. When the engine exhaust gas recirculation system valve is opened.

Symptoms of vehicle malfunctions

The main signal that an error P049C has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.

It can also be warning signs such as:

  1. The Check Engine light on the control panel will illuminate (the code will be written to the ECM memory as a fault).
  2. The vehicle’s engine may run erratically under load or at high speeds.
  3. Increased emissions of harmful substances in the exhaust.
  4. There may be other symptoms as well.

Fault P049C is considered serious because excessive exhaust gas recirculation may cause the engine to stop suddenly while accelerating the vehicle. Unstable idling and starting problems are also possible. It is recommended that this fault be corrected as soon as possible.

Factors that can cause this error code

The error code P049C can mean that one or more of the following problems have occurred:

  • DPFE sensor (EGR differential pressure feedback) is defective and needs to be replaced.
  • The exhaust recirculation pipe is clogged, most likely a buildup of carbon monoxide.
  • Exhaust gas recirculation valve is defective.
  • Due to lack of vacuum, the exhaust recirculation valve cannot open.
  • The exhaust recirculation system temperature sensor does not register the temperature change when the exhaust recirculation valve opens.

How to fix or reset OBD-2 code P049C

When fixing error code P049C, people quite often just replace the exhaust gas recirculation valve. But after that, they get that OBD error back again. The exhaust gas recirculation valve is not always the culprit.

Some suggested steps for troubleshooting and correction:

  1. Use a vacuum pump, open the exhaust recirculation valve, monitoring the engine RPM and DPFE voltage. There should be a noticeable difference in RPM when the EGR is open.
  2. Clean the exhaust recirculation valve as well as the tubing to remove deposits.
  3. Check voltage at DPFE, compare with specified values in your specific model’s repair manual.
  4. Replace the DPFE sensor.
  5. Replace the exhaust recirculation valve.

Diagnose and repair of problems

First you need to read all saved data and error codes with the scanner. Then clear the error codes and test-drive the vehicle. To find out if error P049C appears again.

Check the vacuum lines, wires, and connectors going to the exhaust gas recirculation valve. Also check the control solenoid valve and the exhaust gas recirculation system temperature sensor.

After that, check the operation of the exhaust recirculation system valve. It is also worth checking the operation of the exhaust gas recirculation system temperature sensor. The temperature sensor should change when the exhaust gas recirculation valve is opened.

Then remove the valve and the exhaust gas recirculation temperature sensor. Check for excessive carbon buildup and clogging of the system ducts.

On which vehicles does this problem occur most frequently

Fault code P049C can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:

  • Audi
  • Chevrolet
  • Dodge
  • Ford
  • Mazda
  • Mitsubishi
  • Nissan
  • Subaru
  • Toyota
  • Volkswagen
  • Volvo

Fault code P049C can sometimes be found with other errors. The most common are the following: P042E, P049A, P049B, P049E.

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