CEL code P133

[James Morse]

On the '99 Mazda B3000. Advance says it's O2 sensor, they want $55 for it.

Looked at a couple vids, doesn't look like mine, would appreciate its location, tool needed (22mm open end?), and how to reset CEL after.

I'm hoping this is easy. Should be just take of connectors, take out sensor, put new, reconnect. Could be loose connection I suppose but who knows when it was changed if ever.

 

[RonD]

P0133 02 Sensor Circuit Slow Response (Bank 1 Sensor 1)

Bank 1 Sensor 1 is the upstream(nearest exhaust manifold) O2 on the passenger side of a V6 engine

Code indicates "slow response" not no response so not a loose connection,
i.e. P0134 02 Sensor Circuit No Activity Detected (Bank I Sensor 1)

O2 sensors are the only sensors that wear out, 12 years or 100k miles and they start to run out of chemicals to detect Oxygen in the exhaust
As they run out of chemicals MPG slowly goes down over the years, so way cheaper to change them sooner than later when time is up, 12 years or 100k miles
Gas prices are just too high and O2 sensors too cheap to delay it

I would change BOTH upstream O2 sensors, or all 3 would be even better while the tools are out

7/8" or 22mm wrench will work
Since O2s come with wiring and round connector attached you need to use an open end or flare nut wrench

BUT..........when removing the old one you CAN cut the wires at the sensor to use a deep socket or box end wrench if it's rusted a bit

You can buy O2 sensor wrenches that are socket wrenches with a slot to allow wire harness pass-thru

 

[James Morse]

Thanks Ron. Mileage has been pretty bad, but I just chalked it up to the fact it's almost all in-town driving. Since gas is 3.30 here for branded, I don't see it as really high plus I only drove 1,000 miles in a year in it last year so I'm not sinking a ton into fuel, however, that said, of course I want to get the best mileage I can so sounds like changing all of them would be the way to go and know they are good.

I'll get the slotted socket, I know exactly what you mean it would be the similar to the ones for working with brake lines and they work like a charm.

Will I be able to change out the other 2 easily, meaning, I can get to them without taking other things apart? Where are the other 2?

CEL just came on a couple days after I had it inspected so that was good timing because I bet they won't pass it on inspection with CEL showing.

Anyway regardless of mileage, it'd be wrong to just keep driving as-is because first, it aint right, and second, if the vehicle threw another code, I wouldn't know it if CEL is always on.

 

[James Morse]

These should be the correct ones, and the wrench... pls tell me if that looks right. RA way cheaper than Advance. This a little hard to read if you can't read it let me know I'll re-do.

 

[RonD]

Can't really see it well

But do see 2 downstream O2 sensors and unless you have Factory dual exhaust there should only be 1
I would have a look under the truck to see


The crow foot O2 sensor wrench is a good one to have, like this: https://i.ebayimg.com/images/g/FSYAAOSwgmpjdXHr/s-l1200.webp

Because you can use it from under the exhaust pipe, to loosen the O2, as space can be tight and a socket just won't fit

 

[James Morse]

I don't have dual exhaust and I don't see one on the left side exhaust.

I can't find two upstream sensors.

This should be the one before the cat
More Information for BOSCH 15717 (rockauto.com)
and the one after the cat
More Information for BOSCH 15719 (rockauto.com)

Am I correct that "upstream" means before the cat and "downstream" means after the cat?

I've looked and looked and can't find another upstream sensor, you mentioned there are 2.
The pic in previous post was showing two upstream (L and R) and one downstream., fwiw.
Sorry for my confusion and thanks again.

 

[RonD]

Yes, there will be 2 upstream O2 sensors on any V6 engine after 1992

Yes, upstream is before any Cat converters
Look where the exhaust manifold bolts to exhaust pipe, upstream O2 should be there


Extra credit, lol
Upstream O2s are used by the computer to balance injector open times so engine doesn't run too Rich or too Lean
O2s see Oxygen not fuel, so O2 tells computer the Oxygen content/level after cylinders fire, too little oxygen is Rich, too much oxygen is Lean
When O2s get older they "go Lean", a false Lean, so computer runs engine Richer than needed causing lower MPG

Downstream O2 tells computer if Cats are working well
Cat converters use unburned fuel and the Oxygen to heat up, and this heat burns up pollutants in the exhaust, so downstream O2s should see very little Oxygen left in the exhaust
The computer "feeds" the Cats extra fuel every now and then(via injectors) if downstream O2 shows too much Oxygen left in exhaust, which also lowers MPG as O2 gets older

 

[James Morse]

Thanks.... finally found the driver side sensor.
So I need upstream L and upstream R and downstream then I should be good to go for parts.
Or I could get away with just upstream R for now but might as well do them all or at least do the bad one and keep the other parts on hand.

 

[RonD]

Yes, do all 3 if you don't know when they were last changed

Get the cussing and swearing done in one day

Do upstream one at a time and plug it in then do the next one
Had a shop do my clutch and they reversed the 2 upstream O2 plug-ins, works fine until it warms up, lol
Was throwing Lean code on one bank and Rich on the other, lol, took me a few hours to figure that one out

 

[James Morse]

Um, so the CEL is gone now. Been driving it (the '99) a fair amount, it never came back on. What's that mean? It's ok now, or, just gave up?

 

[RonD]

Bulb finally burned out

Computer can't "give up" so it will set a code when it sees a problem

 

[James Morse]

Seriously? It was on, then, probably hadn't driven it 100 miles tops before it went out, probably less.
You are saying my CEL light (not to be redundant) is burned out, that would be bad because I wouldn't know of any other failure.
How to test? Guess I could have it code-read again and see if code is still there. If it is, and no light, I guess that'd be definitive. Unless something else.
Seems like chance of CEL light burning out is small, but, on the other hand I have faith in your diagnoses.
Not eager to take dash apart so would want to know for sure it's the bulb before going that route.

 

[RonD]

It was a joke
CEL should come on with key on, then go off after startup, that's the Bulb Test

 

[James Morse]

lol yeah I figured that out after I went. Code is "stored but not active" according to the guy at Advance. Meaning I guess, it happened, code was never cleared, but it's not faulting now.
The CEL bulb is fine.
I suppose I can clear the code by disconnecting the battery, right? Then see if it comes back.
I'm totally leery of stuff that "fixes itself" but on the other hand is it possible it had crud on it or something that burned off?
Since they aren't expensive wisest route is probably to replace all 3 sensors per earlier posts. It's 188k miles and who knows if they were ever changed out.
But meanwhile, this isn't something, afaik, that will stop you dead like, say, a failed fuel pump. With new sensors maybe I get a little better performance.
I don't know if they gradually go bad or if it's either they work or they don't.

 

[RonD]

Just get a Bluetooth OBD2 reader for $10-$15, like ELM327
And Torque Pro APP $5
You can then read and clear codes
But also watch Live Data, you see what computer sees from all the sensors

And it works on ANY 1996 and up vehicle, not a Ford thing, ANY vehicle