Q: Error codes, engine light on

asked by on August 01, 2016

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?

Oxygen Sensor Replacement $123.80 - $932.74 Get a Quote
Fuel Injector Replacement $400.56 - $3968.30 Get a Quote
Check Engine Light is on Inspection $94.99 - $114.99 Get a Quote

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.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

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


Experienced Mechanic?

Earn up to $70/hr

What others are asking

Car windows going down, but not up
Hi there. The power windows in your car are computer controlled. They have safety features such as anti-trapping windows. It’s highly irregular that both or all four windows stopped going up at the same time. But when presented with weird...
Car body leans to right & steering pulls to the right
As the vehicle ages, the strut pulse dampeners on the pump may lose some of their gas pressure and require replacement. As far as the ride height, it could be due to the suspension in the right rear being low...
when cranked up it revs up and down
Hello. This is a common issue in the 7.3 Liter Ford Diesels. There is something called an ICP (Injection Control Pressure) sensor (https://www.yourmechanic.com/services/injector-control-pressure-sensor-replacement) which is located at the front of the motor on the driver's side near the fuel filter....
Could it be the coolant sensor?
Hi and thank you for contacting YourMechanic. If your vehicle engine is overheating, there are 3 different things that can cause this problem. The first is the thermostat is not opening up. A stuck thermostat (https://www.yourmechanic.com/services/thermostat-replacement) will cause an engine...
Engine stopped running while driving and will not start again.
Hey there. As you know, this P0340 code (https://www.yourmechanic.com/article/p0340-obd-ii-trouble-code-camshaft-position-sensor-circuit-malfunction-by-jamahl-walker) indicates the camshaft position sensor (https://www.yourmechanic.com/services/camshaft-position-sensor-replacement) is either faulty or not connected properly. The camshaft position sensor monitors the speed of the camshaft providing the ECU with this information. The ECU...
Is $450 reasonable for a timing belt replacement? I have a 2009 Hyundai Elantra.
Hi there. The average cost for a timing Belt replacement is between $259 and $350. This is determined on how the timing belt is replaced and if there are any other issues when removing the timing belt. The thing to...
While driving at a speed of 40 mph all at a sudden the car speed dropped to 10 mph and stopped with solid check engine light
Hello. Warning lights accompanied with stalling can be caused by many things. If the oil is low I would go ahead and top it off to prevent the possibility of engine damage, however, it is unlikely that low oil is...
Able to get my trunk open, by crawling through the back, but the trunk release button (hold unlock button on door) still won't ope
Hello, and thank you for writing in. The first thing we need to determine is if there an issue with the latch, the switch, the key fob, or possibly the wiring. The best way to determine this is to test...
my car heater works and theres no check engine or low coolant light on,but antifreeze leaking into passenger side
Hi Kimala. If the heater is working but you have coolant leaking inside the cabin, then the heater core itself is probably good. However, there are multiple coolant lines that are hidden behind the dash that could have a small...

Related articles

P2173 OBD-II Trouble Code: Throttle Actuator Control System - High Airflow Detected
P2173 code definition Throttle Actuator Control System - High Airflow Detected What the P2173 code means Code P2173 means that there is...
P0346 OBD-II Trouble Code: Camshaft Position Sensor A Circuit Range/Performance (Bank 2)
P0346 P0346 code definition The appearance of the P0346 code indicates that the PCM has detected an incorrect voltage or waveform reading from the engine bank 2 camshaft sensor A camshaft position sensor circuit. What the P0346 code means The...
P0738 OBD-II Trouble Code: TCM Engine Speed Output Circuit Low
P0738 means that the PCM is unable to receive a signal from the engine output speed sensor due to a faulty engine or transmission sensor, or low fluid