Hello All,

I have a mysterious problem going on; its been going on for a while now. For context, I live in South Florida and have a 2019 C300 coupe. I provide its maintenance regularly. About 3 months ago, I received a check engine light with codes P259F (Engine Turbocharger "A" Boost Control Position at High Limit) and P0244 (Engine (Turbo Pressure Relive Valve). My car would not accelerate as strongly as it used to; it was still enough to drive around town, but it wasn't in "limp" mode, as when I pressed on the accelerator, the revs would go up, but my speed would not go up as fast as it would use to. I took it to the mechanic, and they couldn't find the problem as they would drive it and the problem would disappear, so they would clear the code and go on with there day and would tell me that it might be a glitch in the computer system as they would check the turbo pressures and they would be fine. I started to think I was crazy, and only I could feel this loss in accelaration. Then one day at a red light, I turned the car off, then back on, and out of nowhere, the acceleration was back. I quickly realized that the mechanics would never see the issue because they would get the car "warm" so the accelerator functioned properly. I would leave my car at the shop for the whole day because of my work schedule, and by the time I would come to pick it up, the engine would be cold and the problem was back. The check engine light would disappear at times then come back, but they had no correlation with the problem, as sometimes I would have a check engine light but the car would have complete acceleration, and sometimes I would have no check engine light and it would be slugish.

I trust my mechanic, as he is what I think very honest and has never charged me for trying to help me find what is wrong with my car, and his shop only works on Mercedes vehicles and has a well-known reputation for his work.

I did some research and think its the turbo actuator, but I am not sure as it seems to be a sensor issue because the car will work perfectly fine some days and then be slugish some other days. I thought it was just a car needs to be warm, but some days the car on first start will act like nothing is wrong.

Some of my habits with the car are that I never drive without letting it warm up, and I get oil changes every 7k miles. I just hit 100k miles and did a transmission oil change and all of the good stuff that needs to be done in the 100k range.

I will post a video below of whats going on.

 

Hello I have the same issue and the same car. Were you able to find out what was causing the problem? Thanks

 

Same problem on my son's car. Code P259F, comes and goes. Yesterday I witnessed the actuator moving in and out when he started the car. Check engine light was on and I couldn't hear the turbo spin up when he goosed it a little. Either the wastegate is leaking or maybe stuck turbine? Even if the sensor is faulty I would expect to hear the turbo spin up during acceleration.