Code Definition

P1171 — Fuel System Lean During Acceleration

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

About P1171

P1171 is a manufacturer-specific powertrain diagnostic trouble code recorded for Isuzu 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.

P1171 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

Under acceleration the engine demands a large increase in fuel volume to match the additional airflow. DTC P1171 sets when the ECM detects the fuel system going lean during acceleration, meaning the oxygen sensor reports excess oxygen and the fuel trims swing positive while the throttle is opening. This usually reflects a fuel delivery shortfall, such as a weak fuel pump, a restricted filter, or dirty injectors that cannot supply enough fuel under load, though a large vacuum leak or an over reporting airflow signal can also be responsible. The driver may notice hesitation, stumbling, or a flat...

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