P0478 - OBD Trouble Code

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Struggling hard to crack the code? Compose yourself! We are here at your service.

According to the manufacturer’s specifications, and after evaluating the data from the various sensors the PCM calculates the appropriate Exhaust Back Pressure. Subsequently, it compares the value recorded with the actual Exhaust Back Pressure reading which is controlled by the Exhaust Back Pressure Valve. The PCM stores the Error Code P0478 if the actual voltage pressure is too high. Still confused? Don’t worry, we have so much more in store for you!

Consequently, if the PCM stores the Error Code P0478 it signifies that an abnormally high voltage reading has been recorded from the Exhaust Back Pressure Control Valve Circuit. Often this code recorded is associated with the P0479 Code, which registers an intermittently abnormal voltage reading from the same system.

What causes this problem with the Exhaust Pressure Control Valve "A" High

• Defective, burnt, disconnected or loose Electrical Components such as wiring or connectors.
• Damaged or shortened Exhaust Back Pressure Valve Harness.
• Low connection in the Exhaust Back Pressure Valve Circuit.
• Fault in the PCM (Although, that’s least likely to happen)

1. Exhaust Back Pressure System - Facing the error code P0478? An inferior quality Exhaust Back Pressure System can always be dangerous for the system also it is one of the elementary causes behind the occurring of the error code P0478. Tune into Parts Avatar for supreme quality Exhaust Back Pressure System at economical prices.
2. Malfunction Indicator Lamp (MIL) - A distorted Malfunction Indicator Lamp (MIL) can end up being the chief host inviting the Error Code P0478. So, replacing one can be one of the wisest decisions to avoid a problematic system.
3. Powertrain Control Module - also known as the PCM, plays an integral role in overcoming the OBD Error Code P0478. So, a faulty one should be changed immediately from the best quality ones available at affordable prices from Parts Avatar. We are just a click away!

Concerned about knowing the symptoms of the OBD Error code P0478? If yes, then you have arrived at just the right place. We at Parts Avatar have listed out a few common symptoms associated with the Exhaust Pressure Control Valve "A" High –

• The lightening up of the Malfunction Indicator Lamp.
• Insufficient power.
• Deficient Engine Brakes.
• Longer duration of time taken by the cold engine to warm up.

• To begin with, the code should be confirmed/verified using a OBD-II Scanner or an exhaust back pressure step test.
• An attentive visual inspection should be performed of the electrical components in the exhaust back system and the damaged, corroded or disconnected ones should be changed or repaired instantly.
• Now that all possible amendments have been made, to further ensure a road test should be taken to see if the code has been cleared and all the parts have been repaired successfully.
• A resistance test on the solenoid should further be executed, if faulty the solenoid should be changed/repaired instantly.
• A defective exhaust back pressure valve harness should be replaced/repaired.
• After when all the repairs have been made and the code still appears, it becomes important to change the PCM.

Thinking about how to go with the diagnosis of the Error Code P0478? Here listed below is a straightforward process to begin with the entire process

One of the techniques to detect the Error Code P0478 is by carrying out an exhaust back pressure step test. With the help of this test the ECM calculates the pressure values and compare them to the rate at which the pressure deteriorates while the vehicle is running. The results of this test may likely bring out the fault in the exhaust back pressure system.

Common Mistakes When Diagnosing the P0478 Code

Fearing a misdiagnose? Not to worry! We at Parts Avatar have listed here a few common mistakes which will help you further to avoid mistakes leading to an unsuccessful diagnosis –

Because of the Exhaust back pressure tube’ location being near to exhaust gas recirculation valve, it may end up leading to a complete misdiagnose of the Error Code P0478 as relating to one with the EGR system. It should be noted that these two systems should be diagnosed completely in a different manner.

P0475 - Exhaust Pressure Control Valve "A"

P0477 - Exhaust Pressure Control Valve "A" Low