Porsche-specific long-term fuel-trim (mixture) adaptation code. The DME's oxygen-sensing adaptation for bank 1 (cylinders 1-3) has reached its limit - almost always because the engine is running lean and the DME can no longer add enough fuel to compensate. On the M96/M97 flat-six this is the classic 'unmetered air' code and points to an intake/vacuum leak far more often than to a bad O2 sensor. It is very frequently logged together with P1130 (bank 2).
SYMPTOMS
- Check-engine light
- Rough or slightly high/erratic idle
- Hesitation or stumble, especially when cold
- Minor loss of fuel economy
- Occasional hard start
LIKELY CAUSES
- Cracked or collapsed air-oil separator (AOS) diaphragm - the single most common cause on the flat-six
- Torn intake boots, split vacuum lines, or leaking check valves
- Loose/failed oil filler cap or leaking dipstick-tube seal
- Dirty or failing MAF under-reporting airflow
- Intake manifold gasket / O-ring leak
- Weak fuel delivery (failing pump, clogged filter) if lean under load
DIAGNOSIS STEPS
- Read live short- and long-term fuel trims - a large positive LTFT confirms a lean condition
- Smoke-test the intake tract for vacuum leaks (AOS, boots, manifold O-rings)
- Inspect/replace the AOS and check crankcase vacuum with a manometer
- Clean or bench-test the MAF; compare g/s against expected
- Check oil-cap and dipstick-tube seals
- Verify fuel pressure/volume before condemning sensors
- Clear codes and road-test to confirm trims return to normal
RELATED PARTS
- Air-oil separator (AOS)
- Intake boots / vacuum lines
- MAF sensor
- Oil filler cap
- Intake manifold gaskets/O-rings