Skip the auto shop - Our mechanics make house calls

Q: after replacing spark plugs and wires engine light still come on should i replace the O2 sensor as diagnose suggested if so which

asked by on

Engine light on after repacing sparkplugs and wires which sensor do i change as suggested by diagnostic test give by autopart store?

My car has 120000 miles.
My car has an automatic transmission.

A: Hello. If the scanner indicated the O2 sens...

Hello. If the scanner indicated the O2 sensor was bad, I would recommend replacing. The oxygen sensors are located in the exhaust system of the engine, and they sense the oxygen content of the exhaust gases. There should be two O2 sensors on this model engine, one on either side of the catalytic converter.

The sensor located just in front of the catalytic converter measures the mixture of the exhaust gas exiting the engine. The sensor located after the catalytic converter is used to measure the performance of the converter by comparing the O2 levels before and after. (Upstream is the same as pre-catalyst, before the catalytic converter. Downstream is post-catalyst or behind the catalytic converter). The amount of oxygen in the exhaust varies according to the air/fuel ratio of the fuel injection system. The oxygen sensor produces a small voltage signal that is interpreted by the electronic control unit (ECU) of the fuel injection system. The ECU makes constant adjustments in fuel delivery according to the signal generated by the oxygen sensor in order to maintain the optimum air/fuel ratio. If you would like to have this done, a certified technician from YourMechanic can come to your car’s location to replace the oxygen sensor if needed.

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!

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: My car is starting to crank these days But won't turn over.

The crankshaft position sensor on these engines is located behind the crankshaft pulley. The crankshaft pulley on these engines is different than a regular crankshaft pulley and requires a special tool from general motors to remove it. This pulley must...

Q: Location of bank 2 sensor 2 f-150 ford pick-up oxygen sensor

The bank 2 sensor 2 is on your right when facing the truck from the front or drivers side. The sensor is in the exhaust after the catalyst. The bank 2 sensor 1 is just below the exhaust manifold before...

Q: Hello Richard. I have a 2006 E350 and I changed the right caliper and battery on my vehicle and now it won't start. The lights,

Be sure the battery is fully charged. "New" batteries are not necessarily fully charged at time of sale. Of course, confirm that the engine immobilizer system (security system) is not activated. If the starter motor is turning the engine over...

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...
How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...