Skip the auto shop - Our mechanics make house calls

Q: Error codes, engine light on

asked by on

I took the car to the shop and after reading the codes, the car got two error codes. These were: P0140, indicating that the O2 sensor circuit has no activity, Bank 1, and P0171, indicating that the system is too lean, Bank 1. Also, the dashboard shows the engine light on. What does this mean and what should I check and fix?

Hello there. When these codes are seen together, it points to a malfunction in the oxygen sensor bank 1 circuit. This could be caused by many things such as a failing oxygen sensor, leaking fuel injector, rich or lean conditions, or wiring issues. Generally the oxygen sensor codes can cause either a lean or rich condition as the car’s computer attempts to adapt without proper oxygen sensor readings. I recommend having a qualified technician, such as one from YourMechanic, diagnose the Check Engine Light and perform any repairs required.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!
  1. Home
  2. Questions
  3. Error codes, engine light on

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Transmission oil

Hello. Most of the time if you are quoted to service your transmission it will include the fluid in the cost. If you provide your own fluid it is very important that it is the correct fluid that is made...

Q: Signals from my purge valve sensor are intermittent says the diagnosis.

Hi and thanks for contacting YourMechanic. There could be a vacuum leak at the purge valve or around the purge valve. Look to see if the gas cap closed properly, there is no cracks or other damage on the charcoal...

Q: P0300 and P0305. Pending: P0304, P0306, P0171, P0174, P2196, P2198

Hi there. The issue that maybe happening is the are fuel injectors that are not firing and there is a vacuum leak on the engine. Possible multiple sensors are not working causing the P2196 and P2198 codes to appear. For...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.