o2 sensors--replace all?

[D Hook]

Recently my Explorer threw a code for one of the oxygen sensors. My mechanic recommends replacing all four at the same time since it has 168,000 miles on the truck and will probably need them sooner rather than later. About $400 to do all four.

Does that sound like good advice? Labor is only $140 to do them all. Is there a bunch of stuff that has to be removed to get to them? If so, I could see doing all four at once so I don't have to pay labor charges more than once.

 

[boominXplorer]

What was the code? 1/2 the time the o2 sensors will throw a code because of the way the engine is running, not because they are bad.

 

[D Hook]

P0153 - Powertrain
O2 sensor circuit slow response (bank 2 sensor 1)

He did check to be sure the gas cap was on all the way. And it has a rough idle and gas mileage has dropped a bit....maybe by 15%.

I cleared the code once and it came back the next day. Cleared it again (Thursday) and it hasn't come back since.

 

[esclamada]

If you're saving money, you could just replace the upstream sensors (bank 1 sensor 1 and bank 2 sensor 1) the downstream are for emissions checking only, they don't have any effect on your engine. The upstream controls the A/F ratio.



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[D Hook]

That's a good idea. Thanks!

 

[cross6]

It depends on the code. There are specific codes that indicate upstream or downstream. Your mechanic should verify with a scan tool that the 02 sensors are switching properly. That would rule out engine problem causing false 02 code.

 

[esclamada]

It depends on the code. There are specific codes that indicate upstream or downstream. Your mechanic should verify with a scan tool that the 02 sensors are switching properly. That would rule out engine problem causing false 02 code.

the mechanic did as what it says

P0153 - Powertrain
O2 sensor circuit slow response (bank 2 sensor 1)

(upstream are sensor 1, downstream sensor 2)
that's common for worn sensors to not switch properly or send a signal correctly.

 

[cross6]

the mechanic did as what it says

P0153 - Powertrain
O2 sensor circuit slow response (bank 2 sensor 1)

(upstream are sensor 1, downstream sensor 2)
that's common for worn sensors to not switch properly or send a signal correctly.

Whoops, didn't see he posted the actual code further down from original post.

 

[D Hook]

Code came back this morning.

Original question: Am I going to pay the labor twice if I just have them change the upstream sensors now and then do the downstream ones later? Not sure how hard they are to get to.

 

[cross6]

Code came back this morning.

Original question: Am I going to pay the labor twice if I just have them change the upstream sensors now and then do the downstream ones later? Not sure how hard they are to get to.

As stated previously by a poster, the downstream sensors just tell the computer if your cats are working or are present. They don't effect engine management. However, if your state/county requires smog inspection it can be a problem because you will fail. If you don't need to pass smog, the downstream sensors will never be an issue except for a check engine light.

Downstreams are cheaper and usually easier to get to. They will be behind (aft) of the catalytic converters.

When your mechanic replaces the upstream make sure he doesn't use the generic models that require splicing the electrical connector. They usually aren't wide enough for the flex fuel system. OE replacement style motorcraft or denso units seem to work the best from member's experiences. Bosch, not so much.

 

[D Hook]

It's not a flex fuel system so should be okay? I'll request he use Motorcraft parts. I'd prefer to stay OEM anyway.

 

[D Hook]

Had the two upstream O2 sensors changed and have already seen a good increase in MPG. After I run a whole tank through I'll post up the results.