P029909 – Turbo Underboost After Stage 1 Tune (E53 AMG)

Aug 18, 2025 | 10:20 AM

e53_hulu

Thread Starter

Newbie

Joined: Aug 2025

Posts: 2

Likes: 1

E53 AMG W213

P029909 – Turbo Underboost After Stage 1 Tune (E53 AMG)

Hi all,

I’m Octavian owner of the E53_Hulu instagram page, and I’m reaching out to see if anyone has experienced similar issues with their E53 AMG (M256 engine) after a Stage 1 ECU/TCU tune.

Background:

Car: 2019 Mercedes E53 AMG Saloon
Tune: Stage 1 ECU & TCU by Pure Tuning (Jan 2025)
Fault: P029909 – Boost pressure of turbocharger 1 too low (component fault)
Symptoms: Turbo cuts boost completely, no CEL or warning lights, fault clears with OBD scanner or full ignition cycle

Timeline:

First occurred in June during hot weather
Replaced boost pressure sensor behind the turbo – issue resolved
Returned again recently during another hot spell
Smoke test done – no leaks from turbo, intake, or vacuum/boost pipes
Actuator functioning normally

Additional Notes:

Car drives fine otherwise, including launches and mixed driving
Fault only appears in hot ambient conditions
Booked in with Pure Tuning for diagnostics, but looking for insights in the meantime

Questions:

Has anyone else experienced this fault after tuning?
Could this be related to heat soak, sensor drift, or map calibration?
Any known fixes or adjustments that resolved it for you?

Any thoughts or shared experiences would be massively appreciated. Trying to get this sorted before a Europe road trip at the end of the month.

Thanks in advance!

Aug 19, 2025 | 10:30 AM

dagger22

Senior Member

Joined: Feb 2018

Posts: 333

Likes: 102

2019 CLS450 (C257)

Quote:

Originally Posted by e53_hulu

Car: 2019 Mercedes E53 AMG Saloon
Tune: Stage 1 ECU & TCU by Pure Tuning (Jan 2025)
Fault: P029909 – Boost pressure of turbocharger 1 too low (component fault)
Symptoms: Turbo cuts boost completely, no CEL or warning lights, fault clears with OBD scanner or full ignition cycle

Timeline:

First occurred in June during hot weather
Replaced boost pressure sensor behind the turbo – issue resolved
Returned again recently during another hot spell
Smoke test done – no leaks from turbo, intake, or vacuum/boost pipes
Actuator functioning normally

Additional Notes:

Car drives fine otherwise, including launches and mixed driving
Fault only appears in hot ambient conditions
Booked in with Pure Tuning for diagnostics, but looking for insights in the meantime

Questions:

Has anyone else experienced this fault after tuning?
Could this be related to heat soak, sensor drift, or map calibration?
Any known fixes or adjustments that resolved it for you?

Any thoughts or shared experiences would be massively appreciated. Trying to get this sorted before a Europe road trip at the end of the month.

Thanks in advance!

If the last mod you did was the tuning, i would recommend checking back with your tuner on this. It is likely tune related, and if worse case scenario is to revert the tune back to stock and monitor for a period of time.

Aug 20, 2025 | 01:00 PM

figuwx

Senior Member

Joined: Jun 2023

Posts: 425

Likes: 291

2018 AMG E63s Ed1

More than likely, the tuner cranked up the boost pressure to much... it might be taking out the MAP sensor. (this is just a guess though).

Aug 25, 2025 | 05:56 PM

e53_hulu

Thread Starter

Newbie

Joined: Aug 2025

Posts: 2

Likes: 1

E53 AMG W213

Quote:

Originally Posted by dagger22

Quote:

Originally Posted by figuwx

More than likely, the tuner cranked up the boost pressure to much... it might be taking out the MAP sensor. (this is just a guess though).

Thank you both for the advice. I'm going back to the tuner tomorrow to have a deeper look into it. The MAP sensor and higher boost range correlation makes sense as I already charged one MAP sensor. However, the odd thing is that it's triggering the limp mode and fault code when the outside temperature is high (i.e. 28°C plus). It might be a combination of boost pressure and ambient temp. Will keep the forum upadated with what comes out of tomorrow.