P1128 — Long-Term Fuel Trim Mult., Bank 1 System Too Lean
CAUTIONIs it safe to drive? Drive gently and get it looked at soon — it can worsen or fail inspection.
What P1128 means
This is a manufacturer-specific code — its meaning depends on the vehicle’s make (see below).
What P1128 means on specific makes
VW / Audi CAUTION
VW/Audi P1-code: the multiplicative long-term fuel trim on bank 1 has hit its lean limit. Same family as P1136/P1138 — unmetered air or fuel-delivery shortfall. Heavily searched on 1.8T/2.0.
- Vacuum/PCV leak ($50-200)
- MAF sensor drift ($120-300)
- Intake manifold / boot leak ($30-150)
- Fuel pressure/pump weakness
Check first: Same as P1136: smoke-test intake + PCV, check MAF live data and fuel pressure.
Source: Bentley VW/Audi DTC table; PlanetVAG DTC search