Error code

OBD2 P2099

OBD2P2099
Diagnostic Trouble Code· Standard OBD-II fault code read from the vehicle's onboard diagnostics.

What it means

Post Catalyst Fuel Trim System Too Rich.

Severity

severeCan drive, but should address immediately to prevent damage.

Summary

P2099 indicates that the fuel mixture is too rich downstream of the catalytic converter on bank 2.

Symptoms

  • Increased fuel consumption
  • Varying degrees of power loss
  • Rough, erratic, or fluctuating idling
  • Hard starting when hot
  • Fuel odor present
  • Black smoke from tailpipe
  • Engine stumbles upon acceleration

Common Causes

  • Defective catalytic converter
  • Faulty downstream oxygen sensor
  • Exhaust leaks upstream of the catalytic converter
  • Damaged wiring or connectors

Diagnosis

  1. Record all fault codes and freeze frame data.
  2. Inspect oxygen sensors for oil fouling on BMW, Audi, VW, Mercedes-Benz applications.
  3. Resolve other codes stored before P2099 if present.
  4. Test the catalytic converter's operation.

Fixes

  • Replace faulty parts such as the catalytic converter or oxygen sensor.

FAQ

Why is P2099 more common on certain car brands?

P2099 is more likely to appear on BMW, Audi, VW, and Mercedes-Benz due to higher oil consumption rates.

What should I do if there are other codes with P2099?

Resolve the earlier stored codes first before diagnosing P2099.

View source

Not affiliated with OBD2. Answer summarized from the manufacturer's manual linked above; consult that source for the authoritative procedure.

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