Code Definition

P1148 — Heated Oxygen Sensor 1 bank 2 too rich

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

About P1148

P1148 is a manufacturer-specific powertrain diagnostic trouble code recorded for Volkswagen vehicles. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P1148 is stored, the module has detected a bank-specific fault, meaning it applies only to one cylinder bank of a multi-bank engine; and a sensor-related fault — the reported value from the named sensor is out of spec.

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.

P1148 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

The upstream heated oxygen sensor on Bank 2, identified as sensor 1, measures the oxygen content of the exhaust so the Engine Control Module (ECM) can trim fuelling to the correct mixture. DTC P1148 is stored when this sensor reports a persistently rich mixture on Bank 2 that the fuel control cannot correct. The cause may be a genuine rich condition such as high fuel pressure, a leaking injector, or excess vapour, or the sensor itself may be biased rich. When this code is active the driver may notice a fuel smell, black exhaust, rough idle, poor fuel economy, and an illuminated check engine la...

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