Diagnostic Help: Mercedes-Benz/Jeep P0299 Turbo Underboost Fault

The P0299 fault code relates to a "Turbo Underboost" issue, meaning the boost pressure is lower than expected. The problem plagues a variety of makes and models but specifically here we'll focus on Mercedes-Benz & Jeep models fitted with a Hella Turbo Actuator.

This part was widely used with 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'll discuss the meaning, symptoms, causes and solutions of P0299 fault code, with extra attention to problems with the turbo actuator.

What does the P0299 fault code mean?

A turbocharger forces compressed are into the engine's intake, allowing more efficient combustion and more power. The P0299 fault code means that the boost pressure required is not achieved, although this could indicate a faulty turbo; often, the issue lies with other parts of the system.

P0299 Fault Code Symptoms

P0299 symptoms range from a power reduction to slow acceleration, and the activation of the engine malfunction light (MIL). In some cases, the engine goes into limp mode.

Possible causes of this Mercedes-Benz & Jeep Fault Code

There are several possible causes of the P0299 fault code. First and foremost is a problem with the turbo actuator. In addition, boost or vacuum leaks can lead to a reduction in boost pressure. For example, torn hoses or a blocked intercooler could be the cause.

Contamination is also a potential issue to contend with: a clogged DPF filter or a blocked catalytic converter can hinder the turbo's ability to operate optimally. Similarly, a seized turbo actuator or defective sensors can also cause the issue.

Diagnosis: The Steps

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 the P0299 fault code can have various causes, in most cases, a faulty turbo actuator turns out to be the problem. ACTRONICS offers a sustainable, cost-effective remanufacture for the Hella Turbo Actuator.

During the process, loose connections on the PCB, wear on the gears, and other faults are addressed. By choosing to repair over replace, you're not only picking a cost-effective solution, but a sustainable one too. Backed by a two-year warranty, ACTRONICS is always on hand to help.

Would you like to know more about our remanufacturing solutions? Our business technical helpdesk is available! Contact us for more information!