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EPC Light and Loss of Power on my 2018 Q5 2.0T – What's going on?

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Mike T. · rep 0 · May 26, 3:47 AM · 1 replies · solved · Question

Vehicle: 2018 Audi Q5 2.0T Premium Plus

Hey everyone,

I've been having a frustrating issue with my 2018 Audi Q5 2.0T Premium Plus lately. While driving, especially when trying to accelerate, the EPC light comes on, sometimes accompanied by the check engine light. When this happens, the car immediately goes into a 'limp mode' with significantly reduced power.

I scanned it with an OBD-II reader, and it pulled a P0299 code, which points to 'Turbocharger/Supercharger Underboost'. Has anyone else experienced this with their Q5? What was the fix? I'm hoping it's not something too major.

Any advice or shared experiences would be greatly appreciated!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 26, 3:47 AM

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ClearTheCode admin answer:

An EPC (Electronic Power Control) light combined with a P0299 code on your 2018 Audi Q5 2.0T points directly to an issue with the engine's boost pressure system. This is a common problem with turbocharged engines and can have several causes.

Common Causes for P0299 Underboost:

  1. Turbocharger Wastegate Actuator Failure: The actuator arm can become seized or faulty, preventing the wastegate from closing properly, leading to a loss of boost pressure.
  2. Diverter Valve (PCV Valve) Issues: A torn or failing diverter valve diaphragm can leak boost pressure. While less common on newer models, it's still a possibility.
  3. Boost Leak (Cracked Hoses/Pipes): Any crack or loose connection in the intake system, charge pipes, or intercooler can cause a significant loss of boost.
  4. N75 Boost Pressure Control Valve: This solenoid regulates boost pressure. If it fails, it can lead to incorrect boost levels.
  5. Turbocharger Failure: In more severe cases, the turbocharger itself could be failing, though this is often accompanied by other symptoms like excessive smoke or noise.

What to do:

  1. Inspect Visible Hoses: Check all visible vacuum lines and charge pipes for cracks, tears, or loose connections. Pay close attention to the connections around the turbo and intercooler.
  2. Listen for Leaks: With the engine running, listen for any hissing sounds, which could indicate a boost leak.
  3. Check Diverter Valve: While often requiring some disassembly, a visual inspection for tears in the diaphragm is a good first step.
  4. Professional Diagnosis: Given the complexity of the turbo system, it's highly recommended to have a qualified Audi technician perform a thorough diagnosis. They can perform a smoke test to identify leaks, check actuator function with diagnostic tools, and pinpoint the exact component failure.

When to See a Shop:

You should schedule an appointment with an Audi specialist as soon as possible. Driving with an underboost condition can lead to reduced performance, increased fuel consumption, and potentially further damage if the engine is not receiving proper air-fuel mixtures. A professional can accurately diagnose and repair the issue, ensuring your Q5 runs optimally.

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