Code 25 Lean - and VAF testing. (1 Viewer)
- Thread starter danman78
- Start date
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Well, FSM says code 25 happens when:
(1) Heated oxygen sensor output at 2,000 rpm is less than 0.45 V for at least 90 seconds when warmed up. Applies only to code 25 and for California models, excepting high-altitude areas.
(2) When the engine speed varies by more than 15 rpm over the preceding crank angle period during a period of 30 seconds during idling with the intake air, temp. 0C (32F) or above.
(3) When the difference between the air-fuel ratio feed back compensation
value of the front and rear exceeds 15% of the two values in a period of 10 seconds while the engine speed is 2,000 rpm or more and the engine coolant temp. is ’between 70C (158F) and 95C (2030F). ’ *6 (2 trip detection logic) (1) - (3)
With the following suspected trouble areas:
Engine ground bolt loose
Open in Ell circuit
Injector circuit
Injector
Fuel line pressure
VAF meter
PAIR system
Heated oxygen sensor circuits
Heated oxygen sensors
Ignition system
ECM
But i already gave you that PDF. Did you go through the diagnostic procedures in it for code 25?
Here is the PDF for the VAF
(1) Heated oxygen sensor output at 2,000 rpm is less than 0.45 V for at least 90 seconds when warmed up. Applies only to code 25 and for California models, excepting high-altitude areas.
(2) When the engine speed varies by more than 15 rpm over the preceding crank angle period during a period of 30 seconds during idling with the intake air, temp. 0C (32F) or above.
(3) When the difference between the air-fuel ratio feed back compensation
value of the front and rear exceeds 15% of the two values in a period of 10 seconds while the engine speed is 2,000 rpm or more and the engine coolant temp. is ’between 70C (158F) and 95C (2030F). ’ *6 (2 trip detection logic) (1) - (3)
With the following suspected trouble areas:
Engine ground bolt loose
Open in Ell circuit
Injector circuit
Injector
Fuel line pressure
VAF meter
PAIR system
Heated oxygen sensor circuits
Heated oxygen sensors
Ignition system
ECM
But i already gave you that PDF. Did you go through the diagnostic procedures in it for code 25?
Here is the PDF for the VAF
Bad juju...
- Thread starter
- #6
Okay when you say Bosch bad juju well I just took it to a shop and they said they won't even touch it unless it has OME 02 sensors... If there truly is in compatibility issue is there anyway that I can get maybe Toyota or somebody to officially recognize that so that I can potentially return these o2 sensors. Or am I just dealing with a check engine light and no real affect on the performance of my truck?
Lean condition is what I had when my air intake hose had a good size crack in it. It was letting in un-metered air.
- Thread starter
- #8
Yesterday I ran a DMM over the VAF. All the appropriate resistance is we're measured however when I measured the resistance of E2 and VS while operating the Gate there was no change and resistance whatsoever. So as long as I am measuring the correct pins it looks like I have a bad VAF
- Thread starter
- #9
The manual says that when moving the gate the resistance should measure 20 ohms to 1200 ohms. But moving the gate does not change the value and the entire time it reads 2800 ohms... Can the VAF be repaired anyway are there internal components that I can replace or does the VAF need to be replaced. And if so does anybody know a good source or aftermarket that's it is cheaper than the Toyota replacement they are quoting about 900 dollars
I am having the same problem code 25 sometimes code 26 and running like crap. I have a 93 and tested the VAF and got the same readings as you on the 20k scale 3.02 closed and 2.91 open basically the same, no difference open or closed. What was your end result, did you get this fixed?
Thanks
George
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small exhaust leak in front of o2s possible - pretty common on 93/94's. I have a pinhole- and it trips it occasionally
I will have to refer back to my FSM but are you certain you are probing the right points?
anyway, the VAF works basically under the same principle as a volume knob on a stereo. If you've damaged it, chances are there is no repairing it.
But there are 6 contacts in there, and the FSM only refers to the three closest the engine. So i wonder if you are reading the wrong contacts.
But there are 6 contacts in there, and the FSM only refers to the three closest the engine. So i wonder if you are reading the wrong contacts.
I'm metering the two right terminals.
Ahhhhh, therein lies the rub.
On page EG-292, Air Flow Meter Inspection - the diagram shows VS as the right-most terminal and E2 right next to it.
But back on page EG-290 - On Vehicle Inspection - it shows E2 and VS as terminals 4 and 5 of 6, with terminal 6 - on the far right - being THA.
See what happens when you test terminals 4 and 5 instead of 5 and 6.
Tho it may be blasphemy to say this, I believe there may be an error in the FSM.
OK I'll check when I get home. I Was kinda thinking it might be a typo because danman78 is getting the same readings as me open or closed on the two terminals in FSM between 2800-3000 ohms.
Thanks
George
You guys are correct, I found the same error in my 94 FSM when I was troubleshooting the same exact code. My situation was a bit more involved. First, my PAIR valve was stuck open, essentially flooding the O2 sensors with intake air-hence the detection of a lean condition. So I deleted the Pair Valve alltogether. Put block off plates on the exhaust and removed the valve and silencer. Later on found that my VAF was also going bad so I replaced that with a low mileage used one, no way I would pay the 1100 for a new one. The truck passed Washington State Smog tests with flying colors without the PAIR system FYI. Blocking the PAIR for diagnostic purposes would be easy enough as well. It took me all of 10 minutes to make plates with a drill press, grinder, and band saw.
I see now in the FSM what Slim is talking about, I belive its that way in the 93 and 94 FSM I'll recheck it using the other terminals. I checked my PAIR valve by applying vacume to the valve and then blowing through the intake and it passed, did you do anything more than that? Along with code 25 was your the truck running crappy, and did you have any other codes? (I had a 24 & 26 to) I'm in a rush to get this fixed because it needs to be inspected by months end, and I know it will fail plus the cats are glowing cherry red just driving around town not good!
Some good PAIR delete info is in this post:
https://forum.ih8mud.com/showpost.php?p=7862179&postcount=13
specifically, part numbers for oem blockoff plates, etc.
https://forum.ih8mud.com/showpost.php?p=7862179&postcount=13
specifically, part numbers for oem blockoff plates, etc.
The truck was running poorly, stumbling idle and lack of power. The idle would smooth out as I gave it gas. If your cats are glowing red, there is a very high possibility that you are getting too much o2 back there which would make it burn hotter. and really, the only culprits that I can think of that would introduce a lean mixture would be your VAF, PAIR, or a crack in the intake tube beyond the VAF. One thing that was happening when my PAIR was failed open that you could check really easily:
The silencer can that hangs off of the main Air intake Filter housing, was filling full of condensation. At first I thought it might be a by product of Seattle Snorkel ownership, but it turns out that with the PAIR valve constantly open, the Hot Exhaust gas interacting with the cool intake air was resulting in a ton of condensation gathered up in that little silencer can right off the intake. I would check that for any water, and would feel confident in saying that if you find any, your PAIR could be open more than it should be, (this could also be caused by whatever component tells the PAIR to open up failing as well.) Probably not your issue, but something more to check.
