Fault code P049A – exhaust gas recirculation “B” flow malfunction

Fault code P049A is called “Exhaust Gas Recirculation (EGR) “B” Flow Malfunction” 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 P049A

This Diagnostic Trouble Code (DTC) is a general powertrain code. Error P049A is considered a general code because it applies to all makes and models of vehicles. Although the specific repair steps may vary slightly depending on the model.

Fault code P049A – exhaust gas recirculation

The exhaust gas recirculation (EGR) valve is a vacuum-controlled valve. It regulates the amount of exhaust gas reentering the cylinders.

Stored code P049A means that the Powertrain Control Module (PCM) has detected a malfunction in the “B” exhaust gas recirculation (EGR) system flow. The “B” designation refers to a specific position of the EGR step-down valve.

It is either an electrical problem or a mechanical problem, and may cause code P049A to be stored.

Symptoms of vehicle malfunctions

The main signal that an error P049A 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. Engine malfunction may occur when the vehicle is accelerated.
  3. Increased nitrogen oxide NOx emissions in the exhaust.
  4. Unnoticeable symptom will be increased combustion temperature.

Fault P049A is considered serious because a faulty exhaust gas recirculation valve can cause excessive fuel mixture ignition. This, in turn, can cause damage to the engine pistons and valves. Therefore, it is recommended that this malfunction be corrected as soon as possible.

Factors that can cause this error code

The error code P049A can mean that one or more of the following problems have occurred:

  • The exhaust gas recirculation duct, which limits the flow of exhaust gas into the intake manifold, is clogged.
  • The exhaust gas recirculation solenoid is defective.
  • Faulty wiring or harness of the exhaust recirculation solenoid valve.
  • Vacuum lines are damaged, disconnected from solenoid or EGR valve.
  • The exhaust recirculation system valve is defective.
  • Exhaust gas recirculation system temperature sensor does not register the temperature change when the exhaust gas recirculation valve is opened.

How to fix or reset OBD-2 code P049A

Some suggested steps for troubleshooting and fix the error code P049A:

  1. First read all saved data and error codes with the scan tool.
  2. Then erase the error codes and test-drive the vehicle. To find out if error P049A appears again.
  3. Check the vacuum hoses as well as the wires and connectors going to the exhaust gas recirculation valve. Also check the control solenoid valve and the exhaust gas recirculation system temperature sensor.
  4. After that, check the operation of the exhaust gas recirculation system valve.
  5. Also check the operation of the exhaust gas recirculation temperature sensor. The temperature sensor should change when the exhaust gas recirculation valve is opened.
  6. Then remove the valve and the exhaust gas recirculation temperature sensor. Check for excessive carbon buildup and clogging of the system ducts.

Diagnose and repair of problems

It’s worth checking the service bulletins (TSB) first, for your particular vehicle. Your P049A problem may be a known problem with a known fix described by the manufacturer, this may save you time and money during diagnosis.

Next, using a diagnostic tool, actuate the exhaust gas recirculation valve with the engine running. If the engine does not run evenly, the problem is most likely a faulty wiring or poor contact.

If the engine is running evenly, try manually actuating the exhaust gas recirculation valve. If the engine runs evenly and does not stall, the passages are most likely clogged. It will be necessary to remove the valve and clean all the passages.

Checking the solenoid can usually only be done with a diagnostic tool. This is because most solenoids operate with a voltage duty cycle, not a constant voltage cycle.

Check all vacuum lines, hoses, etc. for wear and tear. Inspect solenoid harness and solenoid for damage. Replace the exhaust gas recirculation valve.

On which vehicles does this problem occur most frequently

Fault code P049A 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 (A8)
  • Chevrolet
  • Dodge
  • Ford
  • Mazda
  • Mercedes-Benz
  • Mitsubishi
  • Nissan
  • Renault
  • Subaru
  • Toyota
  • Volkswagen

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

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