Oxygen sensors and fuel injectors

I recently had a new fuel pump and fuel pump strainer put on my 2000 Toyota RAV 4 which has over 167,000 miles on it. The mechanic said that I need to have new oxygen sensors and fuel injectors installed also. Is this necessary or not? If it is necessary, how much should I be looking to spend for these things?

Is the Check Engine light on?


Yes, the check engine light is on.

If there’s a local Autozone, they will connect a scanner to your vehicle and retrieve any codes stored for free. If you return here with all the code numbers, it can be determined what you need and don’t need.


The oxygen sensors charactoristics do change over a lot miles and if yours have never been replaced I would tend to agree with your mechanic about that. The injectors may not be working as good they should be over so many miles but unless you are having gas mileage problems it may not be necessary. I would see why he feels they need to be changed.

How many oxygen sensors would my car (a 2000 Toyta RAV 4, 4 cyl. automatic) have on it? I was told by my mechanic that they are about $100.00 each. Also, can you tell me what purpose the oxygen sensors have and when do you know when you need to replace them?

Wished I had known how to get the codes - I am failing my smog test because of the oxygen sensor and also the TRG. My tail pipe emissions pass the California Smog Test but 2 lights come on say now 2 shops I have brought the car to and so they must report me as a gross violator! And I am one of the many hippies who got these air standards passed hmmmmf!

One light is the oxygen sensor and the other is the EGR [Exhaust Gas Re-circulation] Sensor. The Service Engine Soon light has been on and I am told by DMV and owner’s manual that this is enough to trigger a smog violation. My manual tells me a non-tightened gas cap, bad gas with low octane, wet electrical system or low charged battery may set this light off.

Right before the test, I had filled full the tank with an off brand cheap gas. Yesterday, I drove the car up Interstate HWY 5 from Sacramento to Chico round trip while having burned enough of the cheap gas to displace it with Chevron Techron with 91 octane and detergent.

I have also put 2 oz of CA40G - a fuel additive that sponsors the Ed Schultz show.

Still, my Service Engine Soon light is on.

Questions- are the 2 lights the shop is seeing -lights that I can see? Is my Service Engine Soon light one of the lights they are seeing?

Advice given to me was that shop installed a new battery- [i had never put a new one in the 5 years I owned it- and I bought it as 2 year old previouly leased car with 10,000 miles on it - Chevy Tracker 2000 2.0 litre]. Also fuel injection service and new air filter. We decided I would re-fuel with good quality gas.

I hardly drive the car and wonder if car is having these problems because I always have used the cheapest gas possible and that the car has been sitting most of the time for now 2 years. [I work online from out of my home and only take the car to the food coop once or twice a week.]

Thank you so much for any ideas you might have on how to get these lights off. The shop’s next step they feel is to diagnose why the lights are on or if the lights/ sensors are broken. I have until the beginning of April to take care of all of this.

I teach and I am now already up to 500 dollars. There is a low income program to help pay from the State of California, but I make too much money for it! - which doesn’t even pay off the student loans…until my death it seems…there are Gold Sheild Stations and Test only stations- I don’t know how these differ from my mechanic. I do feel that I like my mechanic and they are reputable- though they do not specialize in smog tests. Should I take the car to a third dealer?

It sounds like you’re making assumptions on the problem based on your interpretation of a code number. There’s more to it than that. Depending on the code, an O2 sensor code may not necessarily mean the sensor is bad.

As Tester mentioned, drop by an AutoZone, Checkers, or whoever is closest, and have them pull the codes. It’s free.
Post the results back here for discussion.
At this point pulling codes should be step No. 1 and throwing parts at a problem should be put on hold temporarily.

Consider adding a can of Sea Foam to the gas and drive it out it is a great cleaner. Also consider adding 2 ounces to oil as it will clean the valves and rings. This may solve allot of issues. Good luck

How absolutely nice of you to respond and help me out! I am going to tell everyone I know about this site. I’ll let you know how it goes. THX again! I’ll do an internet search to see where I can buy it. :slight_smile:

You may have front and rear sensors. There are usually in front and behind the catalytic convertor and are there to tell the system how well the engine is burning the fuel so the ECU can adjust the fuel mixture as needed.

I have a 1977 and 1978 Cad. Seville. Is there anything I can do to increase the gas mileage of these two cars? Presently, I am getting 8 to 9 miles to a gallon of gas. Are there any adjustments or engine parts that would increase the gas mileage of these cars?

Thank you very much for your efforts on my behalf. It will be truly appreciated!


John Chookasian