P1121 – Fuel Trim Too Rich (BMW)

Description

P1121 BMW indicates the fuel trim is excessively rich.

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Symptoms

  • Poor fuel economy
  • Rough idle
  • Black smoke

Causes

  • Leaking injector
  • Fuel pressure too high
  • MAF fault

Diagnosis

  • Check fuel trims
  • Inspect injectors
  • Test fuel pressure

Repair

  • Replace injector
  • Repair fuel system
  • Replace MAF