P1122 – Mixture Control Fault (BMW)

Description

P1122 BMW indicates the ECU cannot maintain the correct air‑fuel mixture.

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Symptoms

  • Rough idle
  • Hesitation
  • Poor acceleration

Causes

  • Air leak
  • Sensor failure
  • Fuel delivery issue

Diagnosis

  • Check fuel trims
  • Inspect intake
  • Scan DME

Repair

  • Fix intake leaks
  • Replace faulty sensor
  • Repair fuel system