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2014 PORSCHE PANAMERA GTS
4.8L V8•AWD•DCT•gas•M48.70
3 active safety recalls on this vehicle — view recalls
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Repairs0Labor487Torque2173Fluid10DTC1839Battery1Maintenance0Recalls3
P1128moderate severityPowertrain

Long Term Fuel Trim System Too Lean Bank 1

on 2014 Porsche Panamera GTS 4.8L V8 · AWD

What this code means

The ECU detected that the long-term fuel trim for Bank 1 has reached the maximum lean correction limit. The engine is not receiving enough fuel relative to the air charge, and the system cannot add more fuel.

Symptoms

  • Check Engine Light
  • Rough idle
  • Hesitation on acceleration
  • Lean misfire
  • Poor fuel economy

Common causes

  • Vacuum leak on intake side
  • Weak fuel pump
  • Clogged fuel injectors
  • MAF sensor under-reading
  • Intake manifold gasket leak

Diagnostic steps

  1. Perform smoke test for vacuum leaks
  2. Monitor fuel trim values
  3. Test fuel pressure
  4. Clean or test MAF sensor
  5. Inspect intake manifold gasket

Repair notes

Repair vacuum leaks first; then address fuel delivery issues if trims remain lean.

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