Code Definition

P2191 — Richness Regulation Fault

System: Powertrain  |  Type: Generic (OBD-II Standard)  |  Make: Generic

About P2191

P2191 is a generic (obd-ii standard) powertrain diagnostic trouble code. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.

Because P2191 is a generic OBD-II code, its base definition is shared across manufacturers. The specific diagnostic steps, reference values, and repair procedures can vary by vehicle, and the TaT Diagnostic Assistant includes verified procedures submitted by working technicians.

Code Information

The Engine Control Module (ECM) monitors air fuel mixture control using oxygen sensor feedback to maintain stoichiometric combustion. DTC P2191 (known on Citroen and other PSA group vehicles as Richness Regulation Fault, and equivalent to the SAE definition System Too Lean at Higher Load Bank 1) is set when the ECM reaches the maximum positive fuel trim correction limit while attempting to maintain target mixture and is still unable to bring the long term fuel trim within range under higher load conditions. This typically indicates the engine is running lean and the ECM has exhausted its compe...

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