Mercedes GLE Diesel engine issues

That sounds frustrating! I had a similar experience with my GLE. The check engine light was on, and the car felt sluggish. The hissing noise you describe sounds like a leak in the turbo system. The pressure sensor is a likely suspect, especially with the stalling and jerking. The sensor tells the engine how much boost the turbocharger is producing. If it's faulty, the engine won't get the right amount of fuel, leading to all sorts of problems. Did you notice if the noise was louder when the engine was cold?

Thank you for your response. Indeed, the hissing noise does seem more pronounced when the engine is cold. Could you elaborate on your experience with the pressure sensor? Was the check engine light constantly illuminated, and did you observe any other symptoms besides the sluggishness? Also, did you address this by yourself, or did you require professional assistance?

Yes, the check engine light was always on. The sluggishness was the biggest issue, but I also noticed the occasional stall at idle. I wouldn't recommend tackling this yourself unless you're very comfortable working on cars. The pressure sensor is usually located on the intake manifold, which can be tricky to access. Given the symptoms and the potential for damage to the turbocharger, I'd suggest taking it to a workshop for diagnosis. They can confirm the sensor is faulty and check for any other issues with the turbo system.

I appreciate your advice. I took my GLE to a trusted workshop, and after a thorough inspection, they confirmed the boost pressure sensor was indeed faulty due to a defective cable connection. The repair cost was approximately 95€. Replacing the sensor has resolved all the aforementioned issues; the check engine light is now off, the engine runs smoothly, and the fuel consumption has returned to normal. Thank you again for your valuable insights.