Q: O2 sensor on exhaust manifold...is it upstream or downstream...09 Nissan Altima

asked by on

Service Engine Soon light is on and I am getting the Catalytic converter replaced. I just need to know which O2 sensor to buy ? Upstream or downstream ?

My car has 21400 miles.
My car has an automatic transmission.

Hey there, thanks for writing in about your 2009 Nissan Altima. The downstream O2 sensor is the sensor used for catalyst efficiency. It is not the one in the manifold but the one after the converter. If you need help with an oxygen sensor replacement, our technicians can come to your location to install the correct the part.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1,000 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. O2 sensor on exhaust manifold...is it upstream or downstream...09 Nissan Altima

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: Heater not working

Hello. If the heater does not work I always check the coolant level first. If the coolant level for the engine is low then not much coolant will enter the heater core which results in little to no heat. If...

Q: Serpentine belt broke. Dealer is telling me it can wrap around crank and get into engine.What are the odds of that happening?

There is a possibility the belt can wrap around pulleys and the crank. I have seen pieces of belt get behind pulleys and a/c compressor clutches or crankshaft pulleys. If the mechanic inspects the old broken belt they can see...

Q: I will buy a car in the US, and has the powertrain fault indicator on. Is it cheap to fix it?

YourMechanic can dispatch a certified Mechanic to personally inspect the vehicle in the U.S., in a pre-puchase inspection and e-mail a complete report to you. The report would note the specific Diagnostic Trouble Codes associated with the Powertrain issue that...

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...
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the...
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...