What Is P0478 Code On 7.3 Powerstroke: How To Fix?

Ford 7.3L Powerstroke PCM brings several Diagnostic Trouble Codes (DTCs) when there’s something wrong happening. The P0478 is one of the DTCs & it’s about the Exhaust Back Pressure(EBP) system.

If you’re getting the error code P0478 & want to explore it thoroughly, this article is for you. In this article, I’ll be explaining the symptoms, causes & solves of the DTC P0478.

P0478 Code On 7.3 Powerstroke

What Does P0478 Code Means On 7.3L Powerstroke?

P0478 is one of the DTCs of the Ford 7.3L Powerstroke. By definition, this diagnostic trouble code refers to Exhaust Pressure Control Valve High. 

An exhaust back pressure valve (EBPV) closes when it’s cold outside to create an additional EBP for the engine to warm up more quickly. The PCM gets the exhaust pressure related information from various sensors, including the EBPS (Exhaust Back Pressure Sensor). 

When the PCM (Powertrain Control Module) gets a normal reading of the exhaust back pressure from the sensors, but the actual back pressure is higher – it generates the error code P0478. 

Symptoms Of Getting The P0478 Code On A 7.3

You’ll get a bunch of symptoms if you have codes like the P0478. Here are some of the common symptoms of getting the P0478 code on a 7.3L Powerstroke: 

  1. Check Engine Light (CEL) Will Turn On 
  2. Noticeably Lackings In Engine Power
  3. Noticeably Lackings In Engine Braking
  4. Cold Engine Warm-Up Takes Longer Time Than Usual

You’ll get all the symptoms mentioned above if your engine has the error code P0478. 

The Causing Factors Of The Error Code P0478

Like every other DTCs of Ford 7.3L Powerstroke, P0478 also has some causing factors. Here are some of the most common causing factors of the error code P0478. 

  1. Damaged EBP Sensor 
  2. Damaged EBP Valve
  3. Damaged or Sticking VGT Solenoid 
  4. Faulty Wire & Connections
  5. Damaged PCM (Rare Case)

How Serious Is Code P0478 On 7.3L Powerstroke 

The error code P0478 itself isn’t a very severe code. However, you’ll notice performance degradation if you’re getting this code. 

Make sure to clear this code to get the optimum performance possible. Follow the next segment to know how to solve the error code P0478. 

How to Solve P0478 Error Code On 7.3L Powerstroke?

You can solve the P0478 error code on your own with little to no previous experience. Follow this segment to know how to do it. 

Check & Replace Electrical Connections  

First, check the electrical connections of the exhaust pressure valve & sensors. The electrical connection includes wires & connectors. That being said, conduct a thorough visual inspection. 

Look for burnt or corroded wires related to the exhaust back pressure valve & sensor. Consider replacing damaged wires & connectors if needed. Finally, clear the code with a scanner & see if the code returns. 

Clean The EBP Sensor & Tube

If replacing the damaged electrical connections couldn’t fix the code, it’s time to clean the EBP sensor & tube. Use 91% rubbing alcohol & a piece of a soft cloth. 

Wipe out the dirt & debris of the sensor and tube. After cleaning the exhaust back pressure sensor and tube, reset the code with your OBD-II scanner. Do a quick test drive & see if the code returns. 

Replace The VGT Solenoid

A sticking or damaged VGT solenoid can cause the code P0478 to appear. Due to carbon particles & other dirt, the VGT can stick or get damaged. Do a quick check-up of your VGT solenoid before replacing it. 

Follow these three steps to check your VGT solenoid: 

  • Step 1: Locate the VGT solenoid & remove the two connectors covering two male pins. 
  • Step 2: Take your digital volt/ohmmeter & measure the resistance of the solenoid coil. 
  • Step 3: Check if the resistance is between 3.42 & 4.18 Ω. If not, your VGT solenoid must be faulty & require a replacement. 

If you’re ready to replace your VGT solenoid, consider getting a 5mm, 12 point socket before starting the operation. 

After getting your socket, you can follow the seven steps mentioned below to replace your VGT Solenoid: 

  • Step 1: Disconnect the battery by detaching the negative battery cables. 
  • Step 2: Locate the VGT solenoid electrical connector & remove them. They should be around the turbocharger. 
  • Step 3: Locate the VGT solenoid & check for the bracket holding it.  
  • Step 4: The bracket is supported by a 5mm retaining bolt; remove it with a 5mm, 12 point socket. 
  • Step 5: After removing the bracket, gently pull the VGT solenoid outwards. Don’t hesitate to apply force while twisting side-to-side & removing the solenoid; it’s needed. 
  • Step 6: Pour some 15W-40 motor oil in a mug & soak the new VGT solenoid valve & o-rings for a few minutes. 
  • Step 7: Finally, re-install the new VGT solenoid & reconnect the battery. That’s it; you’re all set. 

Caution: As the bracket & retaining bolt are the parts of VGT solenoid replacement, don’t reuse the old parts. 

Now clean the error code with a scanner & run a test drive. Check if the code re-appears. 

Replace The PCM 

If the mentioned troubleshooting method failed to solve the error code P0478, suspect the PCM to be faulty. 

Consider getting expert help while replacing the PCM. You can contact your nearby auto shop or any individual expert in the automobile industry. 

How Much Does It Cost To Solve The Error Code P0478

Depending on your 7.3 problems, the solving cost of P0478 will vary. For your clearer understanding, here is the price chart of the potential replacements: 

  • VGT Solenoid Costs $100 to $200
  • Electrical Connection Costs $100 to $500
  • PCM Will Cost Around $500

If you’re getting everything done from an auto shop or an individual expert, add another $75 to $150 per hour as labor/service fees. 

Common Mistakes While Solving The P0478 Code

If you’re new to the DIY work of the 7.3L Powerstroke, you may commit mistakes while solving the error code P0478. Consider avoiding these common mistakes mentioned below: 

  • Using Old VGT Solenoid Bracket & Retaining Bolt With New Solenoid 
  • Not Checking Everything Else Before Replacing The PCM

Additional Comments To Consider Regarding The P0478 Code 

Though the error code has little to do with the sensors, it’s better to have them checked. Consider checking the EBP sensor & clean or replace it. 

Conclusion

I hope this article was helpful enough to know the P0478 code thoroughly. Now you know the possible symptoms, causes & fixes of this error code. 

In summary, the code P0478 isn’t a severe code & you shouldn’t ignore it either – as it directly impacts your overall truck’s performance.

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