Code Definition

P1171 — Fuel system lean during acceleration

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

About P1171

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

During a hard acceleration or power enrichment event the Engine Control Module (ECM) commands additional fuel and expects the oxygen sensors to report a rich mixture. DTC P1171 is set when the ECM monitors the upstream oxygen sensor during this wide open throttle or heavy acceleration condition and finds the signal staying low, indicating the engine has gone lean at exactly the moment it should be richest. The code is therefore a fuel delivery volume test in disguise, as it catches a fuel system that can supply enough fuel at idle and light cruise but runs out of capacity once demand rises. Ty...

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