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internal88, Technician
Category: Audi
Satisfied Customers: 2576
Experience:  I have been repairing Audi vehicles for over 15 years. I specialized in German diagnostic.
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I got a 2004 vw Passat 1.8t with a p0299 code and p0420 code

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I got a 2004 vw Passat 1.8t with a p0299 code and p0420 code

Hello, I'm Brandon - VW tech.

P0299 - turbo under boost.

1. Check for any leaks in the turbo ducting between the turbo pressure side and the intake manifold. Code P0299 indicates the system is showing a low boost condition.

2. Check for movement of the turbo wastegate actuator rod and verify the waste gate does not bind.

3. Verify the turbo overrun shut off valve is not leaking boost pressure and that there is no vacuum present to the valve while under boost.

These engines can be very difficult to locate intake air/vacuum leaks on. The preferred method is to use a smoke machine and fill the intake system by disconnecting the air intake hose at the air filter. Once the system is full of smoke it may further help to locate a leak by using shop air regulated down to 5 PSI and pressurizing the air intake system. Note where there are in-line vacuum check valves and you will have to test that separately as the smoke will not pass these.

Most of the time is a bad turbo, loose turbo hose or intercooler.

The P0420 is catalytic converter efficient code. THis is due to bad catalytic converter. It needs to be replaced.

Please rate me positive for the prompt service,thank you!

Customer: replied 1 year ago.
The turbo was rebuilt last year, I checked the vaccum lines and the waste gate open and closes dosent feel like it binding.

You will need to use a smoke machine to pinpoint the air or vacuum leaks.

Customer: replied 1 year ago.
i dont have a smoke machine,are there any valves that are known to go

The Turbocharger Recirculation Mechanical Valve could go bad.

Also the Wastegate Bypass Regulator Valve N75

Customer: replied 1 year ago.
is there a way to check them with a scan tool?


Have you check the diverter valve? They can have leak and it is common repair. They even have repair kit for them.

Customer: replied 1 year ago.
the diverter valve I took out and hooked up a vaccum gage the valve wont open and and wont hold vaccum so I assume that's the issue

Yes, I would replace that diverter valve first.

Please help me by rating me positive, thank you!

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