Diagnostic help Jeep / Mercedes error code P0299 – Turbo Underboost

Hella Turbo Actuator (Garrett turbo)

Turbo actuators

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Error code P0299 stands for ‘Turbo Underboost’ and means that the turbo pressure is lower than expected. This problem can occur with various car brands and models, but here we focus specifically on Mercedes-Benz and Jeep models with the Hella Turbo Actuator. This part was widely used in Garrett turbos between 2005 and 2015. Models such as the Mercedes C-Class, E-Class, S-Class, Sprinter and Vito, as well as the Jeep (Grand) Cherokee and Wrangler, can be sensitive to this fault. In this article we discuss the meaning, symptoms, causes and solutions of error code P0299, with extra attention to problems with the turbo actuator.

What does error code P0299 mean?

A turbo compresses the intake air and pushes it to the intake side of the engine, which allows overpressure to be generated. This enables more efficient combustion and more power. Error code P0299 means that the desired turbo pressure is not reached. Although this may indicate a defective turbo, the cause often lies in other parts of the system.

Symptoms of error code P0299

Symptoms of error code P0299 can range from reduced engine power and slow acceleration to the activation of the engine malfunction light (MIL). In some cases, the engine goes into emergency mode.

Possible causes of this Jeep and Mercedes error code

Error code P0299 has several possible causes. The first and most important cause is a problem with the actuator. In addition, leaks in the vacuum or turbo system can lead to pressure loss. For example, torn hoses or a defective intercooler can be the cause. Contamination is also a common problem: a clogged diesel particulate filter (DPF) or a blocked catalytic converter can hinder the operation of the turbo, but contamination in the adjustment mechanism of the turbo can also cause problems. Finally, defective sensors, such as the turbo position sensor, can contribute to the occurrence of error code P0299.

Diagnostic steps for error code P0299

You can follow these steps to check what is causing the P0299 fault:

Inspect the air hoses and the intercooler for leaks. A smoke machine can help with this for a quick and accurate detection. Also check the hoses and connections for cracks or other damage
Inspect the particulate filter and the catalytic converter for blockages. Traces of exhaust gas leakage can indicate blockages that affect the operation of the turbo
Clean the VTG / VNT mechanism
Is the complaint still present? Then there is a good chance that the turbo actuator is defective

What to do in case of a defective turbo actuator?

Although error code P0299 can have various causes, in many cases a defective turbo actuator turns out to be the problem. ACTRONICS offers a sustainable overhaul solution for the Hella Turbo Actuator, which is used in Garrett turbos. During overhaul, known problems, such as loose connections on the printed circuit board and wear on the gears, are addressed. By repairing a defective actuator, you prevent further damage to the turbo or even the engine. A timely overhaul is therefore essential. ACTRONICS offers a 2-year warranty on the overhauled actuator.

Would you like to know more about our overhaul solutions for the Hella Turbo Actuator? Our business technical helpdesk is available on weekdays from 08:00 to 17:00. Contact us for more information!