Code Definition

P1133 — Bank 1 Fuel Control shifted lean (FAOSC)

System: Powertrain  |  Type: Manufacturer-Specific  |  Make: Ford

About P1133

P1133 is a manufacturer-specific powertrain diagnostic trouble code recorded for Ford vehicles. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P1133 is stored, the module has detected a bank-specific fault, meaning it applies only to one cylinder bank of a multi-bank engine.

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.

P1133 is a manufacturer-specific code. The same code string on a different make may have a different meaning. Always confirm the code's definition against the vehicle's service information for the specific make and model under test.

Code Information

This DTC sets when the Powertrain Control Module (PCM) determines, as part of the Fuel Air Oscillation Self Check (FAOSC), that fuel control for Bank 1 has shifted significantly toward the lean side beyond a calibrated threshold. During this self check the PCM evaluates how the upstream oxygen sensor and fuel system respond as the mixture is deliberately oscillated, and a large lean shift means the PCM is continuously adding fuel to keep the upstream sensor switching. The result points to unmetered air entering the engine, insufficient fuel delivery, or an exhaust leak biasing the sensor lean....

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