What does this code mean?
The boost-control monitor detects excessive boost for the calibrated operating condition. P0234 is overboost; P0299 is underboost. Their appearance together does not make them synonymous. The cited Ford monitor and Audi DTC chart distinguish them; thresholds and enable conditions remain engine-specific.
Sources and interpretation [1] [3]
A code identifies a detected condition, not a part that must automatically be replaced.
Before replacing a part
Preserve load, temperature and desired/actual boost data. Use the vehicle's actuator and pressure-control checks before replacing the turbo. Do not apply a universal wastegate adjustment or boost limit from another engine.
Manufacturer communications
1Original wording in English
MERCEDES-BENZ, MERCEDES-MAYBACH
Reported code forms P023400
"MY15+ M278 and M157 Equipped Vehicles with Fault Code ""P023400 – Boost Pressure is Too High"" "
Check vehicle applicability
4A listed vehicle is a research lead. Confirm the engine, production range and software in the manufacturer's information.
Sources and interpretation
These explanations are editorial summaries of the linked manufacturer material. PDF page numbers count from the first file page. Original publications are in English; translations are reference aids. A cited edition is not a claim that it is the manufacturer's latest instruction.
- Audi TT Quick Reference Specification Book · October 2013 ↗
Audi of America · PDF page(s) 135 ·
- 22-NA-002 · P0299/P0234 during cold or freezing temperatures ↗
General Motors · PDF page(s) 1 ·
- 2024–2025 MY OBD System Operation Summary for Gasoline Engines ↗
Ford Motor Company · PDF page(s) 86, 87 ·
Source check date · 2026-10-27
Can I keep driving?
A code alone cannot establish whether driving is safe. A flashing malfunction light, severe shaking, overheating, oil-pressure warning or loss of braking or steering needs prompt attention. Stop in a safe place and seek assistance when control or engine safety is affected. Follow the vehicle handbook.