Code Definition

P1165 — Long term fuel trim 1 bank 1 above rich limit

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

About P1165

P1165 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 P1165 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.

P1165 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 Engine Control Module (ECM) uses the oxygen sensor signal to keep the mixture at stoichiometric, and stores the average of those corrections as long term fuel trim so that it can compensate for engine wear, sensor drift and small leaks. DTC P1165 is set when the long term fuel trim for bank 1 has reached the rich correction limit, meaning the ECM is adding as much extra fuel as its adaptation range allows and still cannot bring the oxygen sensor signal back to target. In practice this points to an underlying lean condition: either the engine is receiving air that has not been measured, or ...

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