Code Definition

P1128 — Long Term Fuel Trim B1 System Too Rich

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

About P1128

P1128 is a manufacturer-specific powertrain diagnostic trouble code recorded for Saab vehicles. 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.

P1128 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

On Saab vehicles, the P1128 fault code indicates the Engine Control Module (ECM) has reduced the long term fuel trim for Bank 1 to the limit of its negative correction, yet the upstream oxygen sensor still reports a rich mixture. The code sets when the long term fuel trim for Bank 1 falls below the allowed correction threshold while the mixture remains rich. This usually means excess fuel is entering the engine through high fuel pressure, leaking injectors, or a purge or crankcase vapour fault, or that the mass air flow sensor is overstating airflow. When this code is set the driver may notice...

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