I have an 03 XtraCab Tacoma with 70,000+kms on it. The Air Fuel Mixture
sensor died recently which made the CEL light up, so I bought a new one off
ebay. It is a Denso brand which is apparently the brand used by Toyota. When
I had the code read prior, the CEL no longer appeared.

So once the new sensor was installed, the CEL remained off which was great
but after 300kms it came on again. Just for kicks, I disconnected the
battery to reset it and reconnected. The light has remained off now for
about 50kms. My question is would a problem still exist despite the CEL not
displaying as a result of the reset I did? or is it safe to assume there
isn't a problem currently.

Thanks

"Brad P" <bradp_xx@hotmail.com> wrote in message
news:g40l87$irh$1@news.datemas.de...
50 km may not be long enough to complete the drive cycle. What made you
think the original sensor was bad? Any particular code? The PCM determines
the sensor is bad if it doesn't switch properly in response ot engine
changes.

Ed

On Jun 26, 2:25*pm, "C. E. White" <cewhi...@mindspring.com> wrote:
The computer's logic demands that the malfunction occur on two
consecutive drive cycles. There is an very specific definition of
drive cycle. It's not just start the engine, warm it up a little and
turn it off. You may not have completed two drive cycles yet. Also,
the problem may only occur under certain conditions which may not have
occurred twice in a row. You also don't know that the code that was
set is an O2 sensor code. You really need to know what code is being
set. Autozone will read it for free. Once you know the code, then
you really need a scan tool to diagnose the problem. An O2 sensor
code doesn't necessarily mean a bad O2 sensor. The scan tool can
display O2 sensor behavior, fuel trim etc. which is critical to
observe in order to get to the root cause of the problem. Good luck.
Al

"al" <abuonag@msn.com> wrote in message
news:3c7b7f65-ae6d-4e7c-9a0a-81903ee7af67@c58g2000hsc.googlegroups.com...
On Jun 26, 2:25 pm, "C. E. White" <cewhi...@mindspring.com> wrote:
The computer's logic demands that the malfunction occur on two
consecutive drive cycles. There is an very specific definition of
drive cycle. It's not just start the engine, warm it up a little and
turn it off. You may not have completed two drive cycles yet. Also,
the problem may only occur under certain conditions which may not have
occurred twice in a row. You also don't know that the code that was
set is an O2 sensor code. You really need to know what code is being
set. Autozone will read it for free. Once you know the code, then
you really need a scan tool to diagnose the problem. An O2 sensor
code doesn't necessarily mean a bad O2 sensor. The scan tool can
display O2 sensor behavior, fuel trim etc. which is critical to
observe in order to get to the root cause of the problem. Good luck.
Al


I didn't have the code read second time around, only the first time the
light came on. The mechanic said it was the O2 sensor, Bank 1. The only
symptoms I experienced at the time was a rough idle at one point and bad gas
mileage on the highway.

Thanks for the clarification guys.

The oxygen sensor is usually the victim and not the villain. Unless
you identify the problem as the sensor heater burnt out or something
specific to the sensor, you need to first rule out: poorly tuned
engine (plugs, valve clearances, timing, vacuum/coolant leaks etc),
and that there are no air leaks into the exhaust pipe upstream of the
sensor. Then you need to verify that the ECU is working properly (that
the signal is getting through the wires), and only then can you really
point to the sensor. Many mechanics merely axe the messenger.

Many local parts stores, at least in the US, will offer OBD-II reader
service for free. They'll clear the codes too. You need to make sure
the codes (including hidden ones in memory) are cleared after engine
component replacement. Ask for the code and post it here.



On Jun 26, 10:58*am, "Brad P" <bradp...@hotmail.com> wrote:

Why do you mess around with a stone axe and hammer when working on your
truck?

AutoZone will pull the codes free of charge using a scan tool tha tis
specifically meant for the job. The scan tool will reset the codes for you
too. You do not have to unplug the battery, then deal with programming the
radio again.

Pull the codes with the scan tool, and know that you are actually woriking
on the right stuff. You can leave the gas cap loose and get a Check Engine
light as a result.





"Brad P" <bradp_xx@hotmail.com> wrote in message
news:g40l87$irh$1@news.datemas.de...

We don't have AutoZone here in Newfoundland.

"Jeff Strickland" <crwlr@verizon.net> wrote in message
news:g46b5e$5co$1@registered.motzarella.org...

"Brad P" <bradp_xx@hotmail.com> wrote in message
news:g40l87$irh$1@news.datemas.de...
I booked an appt with DoWal as they can do a scan for $20, but now my CEL
went off on its own yesterday as I didn't touch anything this time. So I'm
not sure now if they'll be able to determine anything.