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Roman, Technician
Category: Audi
Satisfied Customers: 556
Experience:  over 20 years vw audi and porsche technical repair
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Audi: I have 2003 audi a4 1.8t 5 speed. Fault code p0299 turbo

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I have 2003 audi a4 1.8t 5 speed. Fault code p0299 turbo underboost. I have replaced diverter valve and N75 solenoid is "clicking" What could be up here?

Roman :

Hello , Here to answer automotive questions and make you feel comfortable and become familiar with your product

Roman :

the only part left that you did not change is the Faulty charge Air pressure sensor

Roman :

Did you test the MAF ssensor

Roman :

what engine do you have ? did you test the waste gate on the turbo ?

Roman :

16683/P0299/000665 - Boost Pressure Regulation: Control Range Not Reached

Possible Symptoms

  • Reduced Power Output

  • Limp Mode

Possible Causes

  • Hoses/Pipes incorrect connected, disconnected or leaking

  • Charger Pressure Control defective

  • Turbocharger faulty

  • Diverter Valve faulty

Possible Solutions

  • Check Hoses/Pipes to/between Components

  • Check / Clean / Replace Charge Pressure Control

  • Check Turbocharger

  • Check Diverter Valve

Special Notes

  • When found in 2.0l TFSI:

    • Check Boost Pressure Control Valve (N249), for cracked rubber diaphragm. A new/optimized Valve is available under Part # XXXXX (or newer).

      • RoW vehicles see: TPI(NNN) NNN-NNNNfor details.

      • NAR vehicles see: TSB 01-07-70 or(NNN) NNN-NNNNfor details.

  • If the Turbocharger is faulty due to mechanical / internal problems or the exhaust system is restricted (typically the Catalyst) this fault may be the end result.


No test on MAF


No test on MAF its not in limp mode . its drives good but just not that 1.8t boost it shoul have. dv replace . n75 working I bypassed N249 which many people do to see if its that valve

Roman :

so your saying that it does not have a check engine light on ?

Roman :

check to make sure that the hoses to the turbo condenser are tight and not leaking

Roman :

check the turbo wastegate, it will not throw a code

Roman :

what engine in the car


1.8t no leaks

Roman :

then you must test the turbo wastegate. remove the hose from the wastegate and blow shop air into ot and see if it works.

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