Code
P1128
VW / Audi fuel trim
Long-term fuel trim bank 1 too lean
VW generic: bank 1 is running too lean for a long time.
Advertisement
Most likely causes
- Vacuum leak
- MAF sensor dirty
- Fuel pressure low
- PCV leak
Symptoms you may notice
- Check engine light
- Rough idle
- Poor economy
Checks to run
- Smoke-test the intake
- Clean the MAF
- Check fuel pressure
Tools you may need
Smoke machine
MAF cleaner
Always diagnose before replacing. Codes share symptoms; confirm the cause with measurements before buying parts.