P0479 Exhaust gas pressure control valve circuit intermittent

P0479 – OBD-II Trouble Code Technical Description

Trouble code P0479 indicates that the PCM has detected intermittent voltage in the exhaust gas pressure control valve circuit.

What does the fault code mean P0479?

Trouble code P0479 indicates intermittent voltage in the exhaust gas pressure control valve circuit. This code usually appears on vehicles with diesel and turbocharged engines that have exhaust gas pressure monitored. In vehicles with diesel or turbocharged engines, the exhaust gas pressure control valve is responsible for controlling the exhaust gas pressure. The PCM automatically calculates the required exhaust gas pressure based on data received from the throttle position sensor, tachometer and other sensors in the form of voltage readings. If the PCM detects that the exhaust gas pressure control valve circuit voltage is intermittent, P0479 will occur.

Possible reasons

Some possible reasons for the P0479 trouble code:

• Malfunctioning Exhaust Gas Pressure Control Valve: The valve may be damaged or faulty, causing the exhaust gas pressure to not adjust properly.
• Circuit Problems: Opens, corrosion, or other damage in the electrical circuit connecting the exhaust gas pressure control valve to the engine control module (PCM) can result in incorrect readings or no signal from the valve.
• Sensor Issues: A malfunction of the throttle position sensor, tachometer, or other sensors that the PCM uses to calculate required exhaust pressure can also cause P0479.
• PCM Software Problems: Incorrect or malfunctioning PCM software can cause the exhaust gas pressure control valve to not operate properly.

What are the symptoms of a fault code? P0479?

Symptoms for DTC P0479 may vary depending on the specific cause and vehicle type:

• The Check Engine error code appears on the car's dashboard.
• Loss of engine power or unstable operation.
• Deteriorating fuel economy.
• Problems with acceleration or slow response to the gas pedal.
• Unusual sounds or vibrations from the engine.
• Increased fuel consumption.
• Unusual odors from the exhaust system.

How to diagnose a fault code P0479?

To diagnose DTC P0479, the following steps are recommended:

1. Check the error code: Use a diagnostic scanner to read the P0479 code and any additional trouble codes that may have appeared. Record the error codes for further analysis.
2. Visual inspection: Inspect the exhaust gas pressure control valve and all electrical connections for visible damage, corrosion, or broken wiring. Make sure all connections are secure.
3. Checking electrical connections: Check the electrical connections of the exhaust gas pressure control valve for good connections and corrosion. If necessary, clean the connections and reconnect the wires.
4. Pressure control valve testing: Use a multimeter to check the resistance and voltage at the exhaust gas pressure control valve. Make sure the resistance meets the manufacturer's specifications.
5. Checking the throttle position sensor: Check the throttle position sensor for proper operation as it may be causing high or low voltage in the exhaust gas pressure control valve circuit.
6. Additional tests: Depending on your specific situation, additional testing of the engine management system and other exhaust system components may be required.
7. Checking mechanical components: If necessary, check the condition of the mechanical components of the exhaust system, such as the exhaust manifold, exhaust gas recirculation system and turbocharging.

After diagnosing and identifying the problem, it is necessary to carry out the appropriate repairs or replacement of faulty components.

Diagnostic errors

When diagnosing DTC P0479, the following errors may occur:

• Skip visual inspection: An error may occur if a careful visual inspection of the exhaust gas pressure control valve and its electrical connections is not carried out. Skipping this step may result in undiagnosed damage or broken wiring.
• Incorrect component testing: The error occurs when testing is done with the wrong tool or method. Using a multimeter incorrectly or not understanding the system properly can lead to incorrect conclusions.
• Insufficient checking of the throttle position sensor: If the throttle position sensor has not been adequately tested, it may result in undiagnosed voltage problems in the exhaust gas pressure control valve circuit.
• Skip additional tests: Some problems, such as problems with the engine management system or mechanical damage to the exhaust system, may be missed during diagnosis if additional tests and inspections are not performed.
• Misinterpretation of data: The error occurs when test results are misinterpreted or ignored. Insufficient attention to detail or incorrect interpretation of data can lead to incorrect conclusions about the causes of the malfunction.

For a successful diagnosis, you must carefully monitor all stages of the process, use the correct methods and tools, and perform all necessary tests and checks to identify the correct cause of the problem.

How serious is the fault code? P0479?

Trouble code P0479 indicates a problem with the exhaust gas pressure control valve, which can negatively affect engine performance. Although this is not a critical fault, it still requires careful attention and immediate repair.

If the exhaust gas pressure control valve is not functioning properly, it can cause the EGR system to malfunction and ultimately impair the vehicle's environmental performance. In addition, it can also lead to decreased engine performance and increased fuel consumption.

Although P0479 is not an emergency, it is recommended that it be repaired as soon as possible to avoid additional problems and maintain optimal vehicle performance.

What repairs will resolve the P0479 code?

To resolve DTC P0479, perform the following repair steps:

1. Checking the electrical circuit: First, you need to check the electrical circuit connecting the exhaust gas pressure control valve to the engine control module (PCM). Check the integrity of the wires, contacts and connectors for corrosion, damage or breaks.
2. Checking the pressure control valve: Next, you should check the exhaust gas pressure control valve itself for correct operation. If necessary, the valve should be replaced.
3. Diagnostics using a scanner: The use of a diagnostic scanner will allow you to check the operation of the valve and detect any failures or malfunctions in its functioning. This will allow you to more accurately determine the cause of the P0479 code.
4. Replacing the pressure sensor: In some cases, the cause of the error may be a malfunction of the exhaust gas pressure sensor. If this is confirmed during the diagnostic process, this sensor should be replaced.
5. PCM firmware: In some cases, updating the engine control module (PCM) software may help resolve the P0479 code problem.
6. Checking vacuum tubes and hoses: Check the condition of the vacuum tubes and hoses connecting the exhaust gas pressure control valve to other system components. Ensure their integrity and absence of leaks.

It is recommended that you perform these steps under the guidance of an experienced auto mechanic or auto service technician, especially if you do not have much experience in auto repair or working with electrical systems.

P0479 Exhaust Pressure Control Valve "A" Intermittent 🟢 Trouble Code Symptoms Causes Solutions

P0479 – Brand-specific information

Trouble code P0479 relates to the exhaust gas pressure control system and can be common to different brands of cars, several brands of cars with codes for P0479:

1. Ford, Lincoln, Mercury: Intermittent signal from the exhaust gas pressure sensor.
2. Chevrolet, GMC, Cadillac, Buick: Intermittent voltage in the exhaust gas pressure control valve circuit.
3. Dodge, Jeep, Chrysler: Intermittent signal from the exhaust gas pressure control valve.
4. Toyota, Lexus: Exhaust gas recirculation (EGR) valve signal intermittent.
5. Volkswagen, Audi, Porsche: Exhaust gas recirculation (EGR) valve signal intermittent.
6. BMW, Mercedes-Benz, Audi: Intermittent voltage in the Exhaust Gas Recirculation (EGR) valve circuit.

Please remember that the specification of fault codes may vary slightly depending on the model, year and market, so it is always recommended to check the specific technical data and repair manuals for your specific vehicle.