Fink

Will that allow my mileage and everything to return to normal and allow me to keep the single cat. setup?

I didn't realize that would work with this type of setup.

Fink

mt_goat

I don't know about the mileage, I guess it depends on what is causing the poor mileage. The ad says "This device works on ALL current US spec Toyotas" so I'd give Gadget a call and ask.

garrett1478

try to get mark (midiwall) back on this thread, he knows a lot, maybe see if he recommends a different ecu. i would think that that would work, getting an ecu from a very similar 4Runner without 2 cat. converters, but i don't know a lot about this stuff...

cootees

The simulator should work and put your mpg back to normal(assuming that that is what it causing it.) I know a lot of the people that use these simulators to completely get rid of the cat and they have no problem with it. The only downside to it is that if your mixture gets off later down the road then your ecu will not throw a code.

Fink

Yeah, I was waiting for midiwall to grace us with his knowledge, I mean this isn't anything urgent I can live with the bad mileage for awhile so I can figure out what is best and plan it out.

Sounds like swapping ECU's or using the O2 sensor simulator are the best ideas so far.

Fink

midiwall

Sorry Chris, I was pretty tied up yesterday.


Okay, so one thing that I think I'm still unclear about is the number of O2 sensors on a dual-cat'd system. Somewhere up above I talked about how the ECU would need a difference indicator in order to be able to say "yay/ney" to a sensor working right. So in theory I'd think that a dual-cat system would need 3 sensors (front for AF/R, then one between the front & rear cat, and one after the rear cat). Did we ever figure that out? The point being, is the ECU actually looking for a 3rd sensor somewhere?

Past that... Given that you're technically trying to run the truck as a single cat system, I would vote on swapping the ECU with one from a non-CA truck. The signal conditioner that's been talked about a couple of times is cool, but it still needs an O2 sensor installed - it's tweaking/conditioning the signal that's there, not replacing it. If the ECU is thinking that it's missing a signal, then this box will _not_ replace it.

Moving back to dual cats is an option of course, but my guess is that you would still have the problem since you're "just" adding a second cat, not another sensor.

One thing that we haven't considered is that the CA ECU is tuned "tighter" for O2 readings than a non-CA ECU. i.e., it's seeing a wider swing from the O2 sensor you have now, and that's what's causing it to throw a code. That could explain why you were fine for a while, then as the sensor "burned in", the swing got wider (which is normal) and now the ECU doesn't like it. This would be another reason to swap-in a non-CA ECU.

Oh, you asked about reprogramming the ECU you have... not a chance. I'd love to be able to do something with mine, but... sigh. I've never seen published hacks about Toyota ECU's.

Moving to a non-Toyota ECU (like the MegaSquirt) is a pretty big job. The MS is a great box with a TON of flexibility, but it's a task to get it running. You'll need the ignition add-on, and you'll have to keep the original ECU as well in order to handle the tranny (you're auto, right?).


So... I think I'd get ready to drop $150+ into a junked ECU from a non-CA truck.

mt_goat

I don't know about his 99, but my 2001 Tacoma dual cat system only has 2 O2 sensors. The first sensor is just before the first cat and is one of those new A/F sensors. The second is just after the second cat.

Fink

Mine is the same as Mt. Goat's, sounds like I need to start digging around for a new ECU. I know NOTHING about these, do you think the salvage yard will be able to remove it for me or will I need to know how to do it ahead of time. Does it matter what the condition of the vehicle is in? As long as the actual ECU is in good shape?

Where the crap IS the ECU? LoL.

Help!

Any other suggestions are welcome, I won't be getting a new ECU til next week or maybe the week after.

Thanks guys!

Fink

garrett1478

ecu is located behind passenger side kick panel, really easy to get to.

unscrew and remove the door sill thing, then remove the kick panel, and its right there behind it.

i've never removed one, but i would guess that its a couple screws and unplugging the main harness and you're good to go.

mt_goat

Mark, is the only reason you didn't recommend the signal conditioner because of your theory that there needs to be 3 O2 sensors? Because at least on my 2001 that is not the case.

midiwall

For removal, it depends on the state. I know that here in WA, there are no real "junk yards" that you can walk into and strip parts on your own. There's a state law that has to do with liability (I think) which prevents it. But, in Chicago, most of the yards were self-strip.

In general, the condition of the vehicle doesn't matter - short of it having been through a fire.

The ECU is _behind_ the glove compartment. You have to pull the box to get to it. I have some pics and babble on my ECT mod page.

EDIT: Garrett's mentioned that the ECU is behind the kick panel... Be sure that we're talking about the same one, there are a couple of "ECU"s. My 96 4Runner has the one you'd need sitting behind the glove box, it's of course possible that your's is somewhere else. I'd wait for one more person to pop in with a deciding vote.


ooo... good question (think, think...). Yes, that would be the basis of my saying "whoa!". The bottom line is that URD's black-box needs an O2 sensor in order to work since it's gonna condition the generated signal and not create it on its own. So, if we're really looking at only two O2 sensors, then it's possible that the conditioner would work. "but"... I'm kinda' likin' my theory about the CA ECU's being tuned for a tighter O2 range swing, so check with Gadget first to be sure that the conditioner will take a wide swing and quiet it down.

Fink

OK...recap.

I need to check with Gadget and ask him if the conditioner will solve my problem. Also, more than likely the ECU that I will be needing to switch out is behind the glove box?

Fink

midiwall

Yeup! The left kick panel is the 4WD and traction control; the right kick is the tranny; the ECU is behind the glove box.

TRDOLMAN

Mark, there are only 2 sensors on a 2 cat system. The front sensor is only an AFR sensor and has nothing to do with the cats. The second sensor is an O2 sensor the ECU uses to compare readings between the AFR sensor and the O2 sensor. The sensors cannot differenciate between the front or rear cat and can't show which one is bad. The difference in voltage or wavelength (can't remember which) between the 2 sensors is picked up by the ECU. If the differences are not enough, the ECU will throw a P0420 code meaning the cat(s) are inefficient. The second sensor "reads" the differences in the exhaust gases after going through both cats and can't tell if the first or second is bad. All it knows is it is above or below a certain threshhold.

4X4Fink---If I were you and wanted to keep running cats I would put a pair of these on:
http://www.car-sound.com/catalog/universal/430.aspx

I really don't know about what these guys are saying about the EXACT measurements of where the cats and O2 sensors are. I moved my second O2 sensor's position and never had a problem. I changed position of the first cat (installed headers) and never had a problem.

If you are tired of all this BS and want it stopped without buying more or different cats----Get the O2 simulator from Gadget:
http://www.urdusa.com/index.php?cPat...8f15abbf92558c
Install this and you will be done with P0420 codes. I ended up removing my cats for performance reasons and installed the URD O2 sim. Works like a champ.

TRDOLMAN

I edited my post Mark. Read it again. Sorry

garrett1478

oops, sorry about that fink. didn't mean to give false info.

Fink

Sweet, so it sounds like the 02 sensor simulator is the answer...awesome!

If everybody agrees that this simulator will work, score! I'll order it right now!

Thanks for the input guys as usual!

Fink

mt_goat

Well you all ready know what I think. I'll be getting one when I swap in a 2001 3.4 engine into my 93 truck because I'm not going to put 2 cats on a 93 truck.

Fink

Well you probably won't need one, unless that engine was a California emissions spec engine.

But it sounds like this simulator will do the trick, I need some more verification before I drop the 100 bucks on it.

Fink

mt_goat

Yeah I'll wait to see if it throws a code. Where are you getting $100? The URD site shows a price of $55.