2006 Toyota Highlander------Is something wrong? and would you buy?

So I am shopping for my sister in law today, and I looked at a well maintained 2006 Toyota Highlander 3.3. $4400

The check engine light is off.
body is in good shape for salty cape cod.
I plug in my actron cp9580 and it says "fatal memory error" etc.
I tried unplugging a few times and whala, it worked.
So I pull this code:
DTCs (Codes)
P0420
Catalyst System Efficiency Below
Threshold Bank 1
P0430
Catalyst System Efficiency Below
Threshold Bank 2

Ok, not what I want to see. The owner was not aware of this even though his mechanic just looked at it in preparation for sale.
So I do a driving test while recording and looking at the O2 sensors for proper response.
Downstream sensors looks recognizable (200mv-800mv) but upstream voltage was between 2.8-5 volts.
So, I grab my scanner danner bible, and open up to section 4 and see that Titania o2 sensors are variable resistors and varies the reference voltage supplied by the PCM. The output voltage is also reversed.
So my first question is: Is this car using a Titania O2?

Moving on, I am looking at my recording frames and I noticed the system was in closed loop, and then went into open loop a couple of times on my test drive?
Question 2: whats up with that?
Finally. When I put the pedal to the floor I expected to see a rich condition on my upstream o2. (800mv on Zirconia) and (low voltage on Titania (1volt?))
I also did not see a nice sine wave on my upstream sensor.
Remember the car has no mil light lit and the owner has never had issues (supposedly)
Any help would be great.

Ps. I forgot to mention the long term and short term where perfect at all rpms

simclardy wrote: So my first question is: Is this car using a Titania O2?

No. It's using a four wire air/fuel ratio (wideband) sensor in both upstream positions. The downstream sensors are conventional, zirconia O2's.

The voltage looks different because these sensors don't work on a 0-1V volt range. 3.3V is stoichiometric, higher is lean, lower is rich - inverse of conventional O2's.

We specifically cover the Toyota/Lexus wideband sensor in another thread. Definitely worth reading:

www.scannerdanner.com/forum/diagnostic-t...-thread.html?start=0

Moving on, I am looking at my recording frames and I noticed the system was in closed loop, and then went into open loop a couple of times on my test drive?
Question 2: whats up with that?

You're likely seeing that during fuel cut deceleration, when you lift off the throttle. You'll also likely see 5V from the upstream air/fuel ratio sensors at the same time (because 5V is super lean with these sensors).

Finally. When I put the pedal to the floor I expected to see a rich condition on my upstream o2. (800mv on Zirconia) and (low voltage on Titania (1volt?))
I also did not see a nice sine wave on my upstream sensor.

Again, this is a function of the upstream air/fuel ratio sensors. :lol: The upstreams will not switch like a conventional O2. Or rather, they DO switch, but across a very small threshold. For diagnostic purposes, their output is a steady, flat line as long as stoichiometry is maintained. You'll see fluctuations during load change, but no switching.

Remember the car has no mil light lit and the owner has never had issues (supposedly)

Uh huh. :silly: FWIW, Toyota catalyst codes are almost always right on the money. If it flagged pending codes for both banks, there's a pretty good chance they'll mature after a few drives.

Not saying false codes don't happen, because they do. Here's an example I found on a Rav4:

www.scannerdanner.com/forum/diagnostic-t...leaning-the-maf.html

As long as the fuel trims are good, no exhaust leaks, and the engine isn't drinking oil/coolant, then it's cat time.

Tyler, thanks for the super fast response.
I just updated my post to say the fuel trims where perfect. I will check out the thread on A/F sensors.

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No problem! If the fuel trims were pretty, then there's not much left to check.

Would I buy it? Eh, probably? :lol: How many miles? Everything else in good shape? I like that generation of Highlander, so I'm willing to overlook some issues if it's mostly solid.

Tyler,
I just read wbo2.com/lsu/lsuworks.htm and that was helpful. I also watched some of Pauls video on troubleshooting af sensor. I think I get the basic idea. I will have to dig into it some more to feel comfortable.
As I was looking at my data I noticed my MAF numbers seem wrong. For instance, I have 3998 rpms, 3.1 calc load% and 0.89 LB/M maf. another slide is
3822 RPM, 100 calc load, 17.33 LB/M. I would think engine speed would dictate air flow not load?

As for the open loop it does seem to be when the Wide band sensor hits 4.997. Once this did not hold true but pretty much. I suspect I just missed the spike with the tool and it did hit 4.9
Thanks again.

The mileage is 169000.

simclardy wrote: As I was looking at my data I noticed my MAF numbers seem wrong. For instance, I have 3998 rpms, 3.1 calc load% and 0.89 LB/M maf. another slide is 3822 RPM, 100 calc load, 17.33 LB/M. I would think engine speed would dictate air flow not load?

You'd think, right? :silly: But what's happening with the throttle between those two slides? I bet the throttle is closed during the first, and near wide open during the second.

The engine can be in fuel cut deceleration mode at 4000 RPM and hardly breathing at all due to the closed throttle plate (very little air entering the engine). Wide open throttle at the same RPM will likely get close to the engines peak volumetric efficiency.

Thanks. That helps me picture it.

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My sister-in-law decided to fix her old car by replacing the transmission. Thanks for the help Tyler. I love learning.

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No problem!

Well done catching those pending cat codes, BTW. What did the owner of the Highlander have to say?

He spoke to his mechanic. Said it was not a problem, worst case scenario he could put some cat cleaner to get past inspection:(
It needed brakes, tires and maybe cats. Not a bad car. I think he would have gone down to 3500-4000 but my sister in law just put all new brakes on her tahoe. It came from Florida with no rust, and the rebuilt trany comes with 3 year warranty for $3000.
She went for the devil she knows. Lol
Thanks again.

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