Q: Q: O2 Sensors

asked by on

I am getting a check engine light. Took to dealer and they said all four O2 sensors came up on diagnostic. They said unlikely that all fail at once reset and told me to drive it. Chk eng light came back on a mile down the road. What should I check?

My car has 170000 miles.
My car has an automatic transmission.

As you may know the oxygen sensors, which are part of your emissions system, read exhaust gases to determine whether or not the appropriate amount of oxygen is present in the exhaust. Based upon this reading, this information is relayed to the car’s engine control unit (ECU), which then makes a determination as to whether or not to add more or less fuel to the engine. When too much or too little oxygen is present, this will cause check engine light to come on. Too much oxygen may be present in the exhaust gas due to things like an exhaust leak, a vacuum leak, a faulty mass air flow sensor (causing a lean fuel condition) or faulty fuel injectors. Too little oxygen in the exhaust gas may be caused by things like a clogged air filter, a failing mass air flow sensor (causing too much fuel to be introduced to the motor), bad fuel injectors or a clogged catalytic converter. When the O2 sensor is not working properly, this will cause false readings to be relayed to the computer causing inaccurate adjustments to be made to the intake and fuel system in your engine. If you want assistance in diagnosing what is the cause of this symptom, a certified YourMechanic technician can come to your location to perform a Check Engine Light is on Inspection on your vehicle and suggest any repairs.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. Q: O2 Sensors

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: Car stopped while I was driving it; Check engine light is also on.

Have your computer checked to see if there is any pending or stored codes. This will lead you to a location on the engine for troubleshooting. There are many symptoms that can contribute to a stalling and no start condition...

Q: Will E85 cause damage to my 2013 Ford F250

Hello. E85 can cause some serious damage to your fuel system, especially to the seals in the system. If you flushed the majority of it out and added fresh diesel then you will more than likely be just fine and...

Q: Which oxygen sensor usually fails first? I don't have a code reader to tell which one is bad.

Hi. In my experience, I haven't really seen one oxygen sensor fail more than the other one. Considering the year of the truck, I would replace all the oxygen sensors on the truck because, if one is going bad, then...

Related articles

What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.