What does this code mean?
The monitored boost is insufficient for the calibrated operating condition. This describes a control result, not proof of a failed turbocharger. Air-path restriction, control-system behavior and environmental conditions must be evaluated within the vehicle procedure. The cited GM bulletin documents an ice-related case with possible reduced power.
Sources and interpretation [1] [3]
A code identifies a detected condition, not a part that must automatically be replaced.
Before replacing a part
Record whether the fault occurs only in cold weather and compare desired with actual boost. Review the exact engine's air path and boost-control tests. A cold-weather bulletin is not evidence that every P0299 requires a turbocharger or software replacement.
Manufacturer wording
Source wording can vary by vehicle and suffix. It is shown as written, not as a universal diagnosis.
P029900Turbo/Super Charger UnderboostManufacturer communications
4Original wording in English
AUDI
Reported code forms P029900
This bulletin contains repair information for when the EPC light is on and there is poor performance with DTC(s) P029900 and/or P023400.
AUDI
Reported code forms P029900
Supersedes Technical Service Bulletin Group 21 number 14-21 dated November 26, 2014. The MIL is on. Customer may report a reduction in power. DTC P029900 (Turbo/Super Charger Underboost) is stored in the engine control…
AUDI
Reported code forms P029900
Supersedes Technical Service Bulletin Group 21 number 14-20 dated November 17, 2014. MIL on. Customer may report a reduction in power. DTC P029900 (Turbo/Super Charger Underboost) is stored in the engine control module…
AUDI
Reported code forms P029900
MIL on. Customer may report a reduction in power. DTC P029900 (Turbo/Super Charger Underboost) is stored in the engine control module (ECM), J623 (address word 01). The circlip connecting the turbo wastegate actuator…
Check vehicle applicability
4A listed vehicle is a research lead. Confirm the engine, production range and software in the manufacturer's information.
| Make | Model | Model year |
|---|---|---|
| Audi | TT ROADSTER | 2018 |
| Audi | TT ROADSTER | 2017 |
| Audi | TT ROADSTER | 2014 |
| Audi | TT ROADSTER | 2013 |
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) 137 ·
- 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.