Code Definition

P1191 — Heated Oxygen Sensor 1 bank 1 & 2 reversed (wrong wiring connections)

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

About P1191

P1191 is a manufacturer-specific powertrain diagnostic trouble code recorded for Audi vehicles. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.

When P1191 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.

P1191 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 fault code is set when the Engine Control Module (ECM) determines that the upstream oxygen sensors for Bank 1 Sensor 1 and Bank 2 Sensor 1 are responding as though their wiring connections have been swapped between the two banks. The ECM uses each upstream sensor to trim fuel for its own bank, and it cross checks sensor response against the fuel and ignition events for that bank to confirm the correct sensor is connected. When the response pattern indicates the Bank 1 and Bank 2 sensors are reversed, often after sensor replacement or a harness repair, the ECM sets this code. The result is...

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