Code 25/26 Process of elimination, tips?

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

Joined
Jun 28, 2007
Threads
3
Messages
41
Been trying to track down this problem for almost a month.
Have a '91 SR5 pickup 4x4 AT. Took it to my mechanic when the CE light came on. Told him it would point to the O2 but that wasn't likely the problem. Maybe it's cause I'm a woman, he ignored me, replaced the O2, told me it tested weak & charged me $291. Woulda been fine if that woulda fixed it (though *I* coulda replaced the O2), but a few days later the CE was back on. I pulled the codes again. 25/26. Took it back to him with some gentle suggestions but he really wasn't into listening. He cleaned the fuel injectors (which was fine but I didn't feel like that was going to do it) and tested for vacuum leaks. He didn't charge me. The CE light came back a few days later. I returned to him but he basically told me he was stumped and to take it somewhere else. That everything he'd tested came back good and he couldn't find a vacuum leak, tho that's what he was suspecting. He *did* mention that two of the spark plug wires were "leaking electricity" but that they tested fine. I noticed they looked like original equip and the truck has 154k miles on it. He said he'd change the cap and wires for another $100.

I went to Pep Boys, got new cap/wires/rotar ($43) and installed them myself just to eliminate that as a possible source of the problem (misfire can cause 25/26 I've read, though the truck has always run great and still does). The metal leads <?> on the inside of the old cap were rusted and the rotar arm was pitted, so I was hoping maybe that'd be it.

The truck runs even smoother now, but today the CE light came back on, just two days after changing the cap/wires. I kind of thought it would.

I would like to take care of this myself if I can. I sense it might be an electrical short, perhaps in the wires running to the O2 sensor? Or maybe a loose ground somewhere?

I sound like I know more than I do. I'm just making my way through. Does it sound like I'm on the right track? Any tips or suggestions? I read someone suggested clearing the codes then starting the engine, and with ti idling, go underneath and wiggle the O2 wires to see if that trips the CE light. Is it better to use one of those screwdriver-looking light testers for conductivity?

Thanks for reading.

Terry "Have Screwdriver will wrench" :beer:
 
Thanks Wristy... the harness looks good. Was taped to a cross-beam in the frame. Took the connector apart and sprayed some WD40 in the old end (connects to truck vs O2) and cleared the codes.

One other oddity... my truck never smokes or smells. But since the mechanic cleaned the FI's, twice when the light has come on, I've gotten out of the truck and been hit by a chemical burning smell from the engine compartment. The 1st time it happened I was reminded of how a big rig smells when it's heading downhill riding brakes, but it actually smells more like a cleaning grease heating up. The emchanic says he spilled a little FI cleaner, but that it woulda burned off before I even got the truck back, and I'd agree. And why is it intermittent? Today I smelled it again after the CE light went on when I stopped by the beach with my windows down. ?? But it doesn't smell every time I get out or drive. Only if the CE light has been on. (Does not smell like sulphur, fuel of exhaust.)
 
Hey, thanks for the welcome! This is the 3.0L V6. (I know! The 22RE is the cult fave.) :)

I've just been spending the last 2 hours reading more links on people who have had this problem. I'm a little bummed that it can be so many different things. Pinched o-rings on the injectors, bad mass air flow sensor, etc. I'd like to pull my plugs to take a look at them but I don't think I can even get to all of them. The physical design of this engine is not maintenance-friendly.

As an aside, the mechanic that worked on it said he found one spark plug loose, so he pulled it to check it out. Said it looked real good, so he put it back. I asked if he did a compression test and he said he didn't think that was it (maybe cause it runs so good?).

Also, he said he checked for vacuum leaks everywhere except he mentioned something about a manifold that runs "under the passenger... " something-or-other that "he couldn't get to." I was too busy wondering why a mechanic was telling me he couldn't get to something to listen closer to exactly why he couldn't get to it. But that makes me think it needs to be checked better for vacuum leaks.
 
Nothing wrong with the 3.0, it's a fine engine, just a pain to work on.... and the headgasket thing.....

Yes, you should clear the codes, you can do this by pulling either the "EFI" fuse that's in the fuse block under the hood for a minute, or by disconnecting the battery for a minute.... But you'll have to reprogram your radio if you do the bat...... :D

I would check your air flow meter, you'll need a multi-meter, a $20-25 one will be fine, to check the resistance in Ohms.

The 7 contacts at the air flow meter are in this order: Fc-E1-E2-Vc-E2-Vs-THA (yes there are 2 "E2" contacts)

The specs should be:

Vs-E2.......... 200-600 ohms
Vc-E2.......... 200-400 Ohms
THA-E2 ....... 10-20K ohms at 4*F
.................. 4-7K Ohms at 32*
.................. 2-3K ohms at 68*
.................. 0.9-1.3k ohms at 104*
.................. 0.4-0.7k ohms at 140*
Fc-E1.......... infinity

That should give you something to do.
 
Thanks for that! Will do tomorrow (or later today as it's past midnight). As for the head gaskets, the previous owner had them replaced with the recall so I never had that hassle, thankfully.
 
I've never had to familiarize myself with this motor, and have no idea where the AFM is, but it isn't for lack of trying! This Chilton manual is nearly useless. Doesn't list an air flow meter, or air flow sensor, or mass air sensor, or vane air flow meter, or any of the other close names that I thought maybe doubled for this. I looked at the few schematics (most are of the 22RE) and did not see anything I could pinpoint either. I googled "air flow meter +3VZE" and saw pictures of a boxy-type container, but that didn't help much. Maybe I should mention this truck has a K&N AF. (I didn't go buy the meter yet b/c I wanted to find the AFM first!) :D Sorry I'm so green.
 
P.S. And I'm going to keep trying to find it, but in case someone answers before I do, I'll keep checking back...
 
Hehe, the air flow meter is at the front drivers side corner of the engine bay, and has a D shaped plastic top that's siliconed in place, there should be a wire harness that plugs into it, and that's where you take it apart and measure the Ohms.
 
Er uh... there's a sort-of D-shaped silicone cap on a metal casing that says "Toyota Speed Control Activation" on it, but that doesn't sound like a AFM and it only has two small harnesses, one with 2 wires, one with 3.

Behind the K&N (actually the metal casing it connects to that leads into the air intake manifold, if I have my terms correct) has a distinct D-shaped metal riser with a harness plugged in there, but that's still only 7 contacts. I can't see an 8-wire harness. :o
 
Oh jeeze... I just saw you wrote "7-contact" in your post. I was counting the ......readings for 8.


Okay, so it's behind the K&N filter, I presume. I think I'll post a pic on my website so you can look?
 
I don't show any reading at all between VS & E2, but I might be doing something wrong. (Don't know what it could be. Meter set to read Ohms in 200 range, probes each on the correct contacts.) But normally problems with the AFM result in code 31 vs 25/26. (No code 31 here.) Plus I'm not sure the standard specs apply b/c my AFM is a K&N, not Toyota.

Thanks for your help though... I'm going to pursue some other avenues like ERG or vacuum leaks. I'll also try to find out what the specs for the K&N AFM are. Will post what the problem was when I find it.
 
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?
 
Doubtful, but don't rule out a clogged cat if nothing else pans out.


Mark...
 
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?


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...
 
Back
Top Bottom