[Sticky] P0171 - System Too Lean (Bank 1)

Description

Indicates that front oxygen sensor (at the input of catalytic converter) detects higher than expected percentage of oxygen in exhaust gasses. Could be due to the unbalanced air-to-fuel proportion at the engine, fault oxygen sensor or other systems.

Symptoms

• Check Engine dashboard light is ON
• Possible lack of power and car dynamic
• Unstable work and sound from engine: stumbles, shakes

Causes

• Faulty or dirty mass air fuel (MAF) sensor
• Malfunctioning fuel pump
• Clogged fuel filter or injectors
• Vacuum leak
• Faulty oxygen sensor
• Leaks in exhaust system

Severity - moderate

Does not have immediate danger effect to the car or driver, but at longer period could lead to engine overheating and damage. .

Troubleshooting

• Check and clean MAF sensor
• Inspect vacuum and air intake systems for leaks
• Inspect and replace, if required, fuel filter
• Inspect and replace, if required, fuel pump
• Review and correct, if required, fuel injectors, exhaust system, other systems that have DTCs.