Porsche-specific multiplicative fuel-trim adaptation code. At higher engine load the mixture correction for bank 1 has reached its adaptation limit. Unlike the idle-range codes (P1128/P1130), this fault is weighted toward part- and full-load metering, so it points more strongly at the MAF, a large vacuum leak, or a fuel-delivery shortfall than at a small idle vacuum leak.
SYMPTOMS
- Check-engine light
- Hesitation or flat spot under acceleration
- Reduced power at higher load
- Worse fuel economy
LIKELY CAUSES
- Dirty or failing MAF (skewed multiplicative correction)
- Large intake/vacuum leak
- Weak fuel delivery (pump, filter, injectors) if lean
- Over-fuelling source such as a leaking injector if rich
- Air-oil separator fault
DIAGNOSIS STEPS
- Log fuel trims across the load range, not just at idle
- Clean or replace the MAF and re-check the multiplicative trim
- Smoke-test the intake
- Verify fuel pressure/volume under load
- Clear and road-test through the affected load range
RELATED PARTS
- MAF sensor
- Air-oil separator (AOS)
- Fuel pump / filter
- Intake boots