Symptom hub
P0171 After Exhaust Work: New Exhaust Leak, O2 Sensor Disturbance, or a True Lean Problem?
When P0171 shows up right after manifold, flex-pipe, catalytic-converter, or O2-sensor work, respect that timing before blaming the fuel pump. A leak ahead of the upstream sensor, a disturbed connector, or the wrong sensor installation can create a lean-looking story immediately after exhaust service even if the engine was not truly fuel-starved beforehand.
Likely related codes
Start your diagnostic path here
P0171 — System Too Lean (Bank 1) P0420 — Catalyst System Efficiency Below Threshold (Bank 1) P0430 — Catalyst System Efficiency Below Threshold (Bank 2) P0135 — O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1) P0141 — O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2) P0136 — O2 Sensor Circuit (Bank 1 Sensor 2) P0137 — O2 Sensor Circuit Low Voltage (Bank 1 Sensor 2) P0156 — O2 Sensor Circuit (Bank 2 Sensor 2) P0157 — O2 Sensor Circuit Low Voltage (Bank 2 Sensor 2) P0139 — O2 Sensor Circuit Slow Response (Bank 1 Sensor 2) P0140 — O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 2) P0159 — O2 Sensor Circuit Slow Response (Bank 2 Sensor 2) P0160 — O2 Sensor Circuit No Activity Detected (Bank 2 Sensor 2) P0421 — Warm Up Catalyst Efficiency Below Threshold (Bank 1) P0431 — Warm Up Catalyst Efficiency Below Threshold (Bank 2)