DTC P0171: 1/1 Fuel System Lean: Description

Fuel system lean condition is monitored with engine running in closed loop mode, ambient/battery temperature at more than 20°F (-6.7°C), and at altitude less than 8000 feet. DTC will set in Powertrain Control Module (PCM) memory when PCM senses fuel system is running too lean on 2 sequential trips. Possible causes for DTC to set are: defective Engine Coolant Temperature (ECT) sensor, engine mechanical problem, fuel pressure out of specification, defective 1/1 Heated Oxygen Sensor (HO2S) heater or fuel system not switching from rich to lean.