Porsche-specific additive fuel-trim adaptation code for bank 1 at lower load. The additive (idle/low-load) mixture correction has hit its limit. On the M96/M97 this is part of the same lean-diagnosis family as P1128 and usually indicates unmetered air entering the intake at idle and light load.
SYMPTOMS
- Check-engine light
- Rough idle
- Hesitation off idle
- Minor economy loss
LIKELY CAUSES
- Air-oil separator (AOS) failure
- Vacuum/intake leak at idle
- Loose oil cap or dipstick-tube seal
- Dirty MAF
- Faulty upstream O2 sensor (less common)
DIAGNOSIS STEPS
- Read additive fuel-trim adaptation at idle
- Smoke-test the intake and replace AOS if torn
- Clean/test the MAF
- Check oil cap and tube seals
- Clear and road-test
RELATED PARTS
- Air-oil separator (AOS)
- Intake boots / vacuum lines
- MAF sensor
- Oil filler cap