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P0299 2.0L turbo VW, Audi

Diagnose and fix P0299 2.0L turbo VW, Audi

Trouble code P0299 2.0L turbo VW, Audi can be caused by many things and it’s a very common code on VW and Audis with the 2.0L turbo engine. Always start your diagnosis by checking for air leaks in the intake system.

What is P0299?

P0299 Turbocharger/Supercharger “A” Underboost Condition

This code set when when the ECM sees a difference in set boost pressure versus actual boost pressure for 6-secs of > 150hPa at engine speeds >2200-2800RPM and altitude <2700m. Boost pressure control active and turbo charger bypass valve closed. When the P0299 code stores, the ECM commands a turbo failsafe limited operating strategy to reduce boost pressure to the minimum to prevent damage that might be caused by excessive boost pressure.

What is Turbo failsafe?

This puts the turbo into a state when it can’t deliver any measurable amount of boost. When you star the engine, it applies vacuum to the turbocharger to move the vanes into a position when it can supply maximum boost. The ECM immediately senses the boost and reduces vacuum as the engine load increases. Thus, any loss of electrical or vacuum will cause a loss of boost pressure.

What causes overboost?

Overboost is most often caused when the vanes in the turbo malfunction and get stuck in a position that causes boost pressure to increase.

What causes underboost?

Underboost can be caused by a bad turbo boost control solenoid, cracked or broken vacuum hoses or any kind of electrical problem in the boost pressure circuit.

The first step in diagnosis involves checking the air intake system for cracks or breaks. If the intake system checks out, these are the most commons issues.

Remove the engine cover and check out these readings.

Check for power at charge air pressure sensor for P0299 trouble code

Disconnect the charge air pressure sensor connector. Connect your meter as shown. Turn key to ON and check for voltages shown. If you don’t see those readings, check for opens, shorts in harness by testing the harness at the ECM.

Next, check for pressure readings. Reconnect connector and backprobe terminal #4 and ground. With the key in the ON position but engine OFF, you should see about 2-volts. The voltage will increase as you add boost pressure.

Check the turbocharger recirculation valve

The turbocharger recirculation valve is a solenoid valve that meters vacuum to the turbo wastegate to open and close it in varying degrees depending on the amount of boost required.  The valve is operated by the ECM with a pulsed voltage. Battery power comes to the valve from the fuel pump relay and the ECM controls the ground to the valve. There are only two terminals on the turbocharger recirculation valve. To test, connect your multimeter and check resistance. You should see 14-20Ω. If not, replace the turbocharger recirculation valve.

Test turbocharger bypass valve

The turbocharger bypass valve diverts boost pressure into the incoming air to the turbo to prevent turbo slowdown. Check for battery power on terminal #1. Check resistance. Should be 27-30Ω.

Test the turbocharger control shutoff valve and wastegate regulating valve

Check the wastegate to ensure it is not leaking at idle. Apply vacuum to the turbocharger control shutoff valve to ensure it’s not leaking.

VW service bulletin TT 21-10-02

VW has issued a service bulletin to address a P0299, P0234 or P0236 trouble code on all 2008-2015 engines with the 2.0L TSI engine.

VW has determined that a roll pin located in the turbocharger exhaust housing might possible back out. That allows the wastegate valve and lever to drop into the housing. The wastegate lever can then become seized in the open or closed position, causing either an underboost or overboost condition. The over/under boost condition can be intermittent, making it hard to duplicate the fault.

Check the wastegate lever for approx. 3mm of clearance between the bottom of the lever and the turbocharger housing. If there is no gap then the turbo must be replaced.

Most common causes of P0299

Boost pressure sensor

Turbocharger recirculation valve

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Posted on by Rick Muscoplat


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