Code 25/26 Process of elimination, tips?

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WristPin said:
what!?

K&N replaces the AFM?


i have never head of such a thing


you can have a shop smoke test your intake systm to find leaks
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I just assumed it was part of the K&N kit b/c of the sticker. (The K&N was on here when I bought the truck.) :doh:

A smoke test? How about I light a cigar and blow smoke into the K&N! :D Or I could hold several sticks of incense in front of the AF. How the heck do they do it? I bet my way smells better. :lol:
 
Mark W said:
25 and 26 at the same time is classic bad O2 sensor indication. I understand why that was the first thing your mechanic looked at.

Did the mechanic check/change both of them?



Mark...
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Hi Mark, he replaced the one forward (and likely checked both). But I read many posts from Toyota techs (one guy worked as a diagnostics tech for over 30 years) before I took the truck in. These guys all basically said the same thing: that when codes 25/26 come up, the first thing most mechanics do is replace the O2, and that it's almost never the O2. That they rarely go bad and are just doing their job, triggering the CEL because of problems they are detecting. That's why I told my mechanic that the codes would point to the O2 as a possible cause, but that it was not likely it. He replaced it anyway and the CEL returned, just like the Toyota techs said.
 
2ndGenToyotaFan said:
Yes, that's the thing in the picture, the K&N Filter just replaces the stock air filter. Does that D shaped cap say "ND" or "Nippondenso" on it? If so it's stock.

The air flow meter tells the EFI syter how much air is coming in so it can adjust the air/fuel ratio. Getting codes 25 and 26 means you have a lean (Too much air) and a rich (Too much fuel) condition, so the air flow meter could be sending mixed signals and creating your problem.

Have you cleared the codes and taken it for a spin?
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Whenever I clear the codes it takes a few days for the 25/26 to be triggered again, so I can't tell right away if I've done something that made a difference. I cleared them last night (Thu) but all I'd done
is spray WD40 into the truck harness that goes to the forward O2 sensor, so I'm not filled with confidence that anything will be different. ;) Today I was really looking forward to testing the AMF, never dreaming it would take all day to locate! (I want a shop manual!! I got so mad I went to eBay to look for one, but the closest I found is for a 1990 4Runner. Same engine, I know, but electrical stuff and other things would be different, so I want a pickup manual.) And I don't understand why I didn't get any readings between E2 and VS. I even found this page
http://tinyurl.com/2xv3mg
to make sure I was doing it right.

But now let me ask a really dumb question (yes it's safe to say there will be a number of these): when I took the harness off the AFM I assumed I should test the harness contacts. But the URL above says if the resistance is not within spec, the unit is bad and should be replaced. How can testing the harness (disconnected from the unit) tell me if the unit is bad? Seems I would need to test the posts on the unit itself? (I know, this is an awful lot of hand holding. It's okay if you bail on me!) :)
 
I've got to differ with that. Every 25/26 I've seen HAS been the O2 sensor(s). They do go bad. Nothing uncommon about that. Their "job" is not really to trigger the CEL, but to allow the ECU to adjust the fuel ratio. If you're showing a lean or a rich code, then something besides the O2 sensor is where to look for the problem. But showing both at the same time is more likely to indicate a bad sensor than it is to indicate a mixture that is fluctuating back and forth beteen the two conditions and triggering both codes.


Mark...
 
Mark W said:
I've got to differ with that. Every 25/26 I've seen HAS been the O2 sensor(s). They do go bad. Nothing uncommon about that. Their "job" is not really to trigger the CEL, but to allow the ECU to adjust the fuel ratio. If you're showing a lean or a rich code, then something besides the O2 sensor is where to look for the problem. But showing both at the same time is more likely to indicate a bad sensor than it is to indicate a mixture that is fluctuating back and forth beteen the two conditions and triggering both codes.


Mark...
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Hey Mark,

Didn't mean to imply they _never_ go bad of course, but the Yota techs were certainly right in my case.

As to possible culprits for the 25/26 rich/lean codes then, an example of the kind of stuff I came across:
http://tinyurl.com/2a3akt
 
Mark W said:
The testing procedures are referring to testing resistance between contacts on the unit, not the matching harness connections.


mark...
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Thanks. Since I suspected as much I'd tested the terminal as well and got zip between E2 and Vs. But I still suspect I'm doing something wrong. For one thing, if the AFM were not working anywhere near spec wouldn't the CEL come on immediately upon the engine warming to normal operating temp?
 
WristPin said:
maybe you should try a new O2.
maybe the last one you got is defective.
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Could be, but seems unlikely for the reason that with all of the things I've done (replacing O2, replacing dist cap/wires/rotar and cleaning fuel injectors ...with a few days between each thing)... the behavior pattern of the way/timing that the CEL reappears [2-3 days later, and sometimes going off, then finally coming on and staying on] has remained consistent. I don't feel I have touched on the cause yet, or even a contributing cause. That's my gut feeling. (The codes are always the same too.)
 
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Yes.

I got this digital multimeter at Pep boys for $19.99. It's bright orange (I'm sure some of you have seen it.) It's the only one they had.

When you turn it on and switch the setting to reading Ohms, you get a 1 on the LCD by default. When I put one probe on the Vs pin, and the other on E2 (either E2 pin), the meter doesn't respond. The "1" remains, but since it doesn't react as if it's getting any reading, I am assuming it's a non-reading.

Same with testing Vs to either E2 pin.

Then I switched the meter setting to read in the 10-20k range to test THA to E2, and I got a 1.86 reading (same for both E2 pins with the THA).

Perhaps another dumb question... I removed the harness by pulling it off the connector. The connector on the AFM is connected by two philips screws. Am I supposed to take this connector off to get to contacts beneath it? (I didn't think so and am just using the pin terminals in the connector for testing.)

I also tried switching which probe I would use when I didn't get a reading... i.e. putting the red probe on the E2 pin first [black on the other], then reversing that. Is there a secret to this?
 
Got it... yes, the Ohm meter (as you already know) should have been set to 2000 Ohms to read in the 200-600 range... not set to the 200-ohm range. So with the meter set to 2000 ohms:

Vs to E2 (using either E2 pin) reads 355 ohms.
Vc to E2 (using either E2 pin) reads 277 ohms.

Both within spec albeit on the lower side.
 
WristPin said:
i just checked he pic

sticker is only to state that the filter is re usable.

not cause K&N makes a AFM
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I knew I would have noticed if it was just one of those K&N stickers that tells you not to discard the filter. :) It says K&N Injection Performance Kit Carb D-269 [with a stamped] 8 into a metal tag. Then it has K&Ns address. However, behind the D-shaped riser on the main body of the AMF there is a standard Toy/Denso sticker.
 
Thanks Wristy. I may end up doing that. What a great idea to find vacuum leaks.

To Jerod:

From your earlier post:

Vs-E2.......... 200-600 ohms
[MR: 355]

Vc-E2.......... 200-400 Ohms
[MR: 277]

THA-E2 .......
.................. 2-3K ohms at 68*
.................. 0.9-1.3k ohms at 104*
[MR: 1.86 @ ~85-90F, so this seems good too]


Fc-E1.......... infinity
Not sure where to set the meter to test for a response of infinity, so I didn't get a reading here. (i.e. I tried a few settings and got no response.)
 
you got it right, infinity shows no change on the display. like it would if the probes were not connected to any thing.

its like saying open. but they dont say open cause than usally is refered to a circuit than can be open and closed. or related to a break or short in the circuit.
 
Thanks again Wristy.

I was reading through the Chilton manual last night in bed (yes, this is one exciting life!) and after studying the fuel schematic and trying to get a feel for what might be the culprit, I thought maybe I'd look at the throttle body next. The truck starts right up (and always has) so I don't think it's the cold fuel injector. Once (literally one time) a couple weeks into this after the codes had been reset and after replacing the O2, just as I rolled into a parking spot (basically at an idle) I got a real rough idle but it only lasted a second or so... the truck resumed normal idle by the time I was ready to put it in Park, however it triggered the engine light. This also makes me suspect the throttle body (possibly gunked up?) or ... ? [OTOH I did change the cap/wires/rotar since then which could have been the problem.]

Any suggestions/words of wisdom will be collected in a bucket and much appreciated. :D
 
Well, I'm glad that your AFM is ok, cause they can be expensive! You may want to check your TPS (Throttle position sensor) while you have the multi meter out... Just check the specs first, then if it's out of adjustment loosen up the screws and mess with it, but it's a very finicky thing to adjust. Here's everything you need to know about TPS checking/adjustment:

http://www.4crawler.com/4x4/CheapTricks/TPS/index.shtml

I don't think the TPS is your problem, but it's good to check it anyway.
 
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