mischief2jz

hello all, been reading on this forum for a long time, first time posting...

I have done a lot of research on this topic but have yet to find a solution

So a brief background, I have a 1993 3vze auto (awful I know) it has about 195k on it, and about 10k ago I had a complete upper end rebuild done, head gaskets, valve seats, cam bearings, new distributer and wires, etc
Starting about 500 miles ago I was getting code 14 and 25, seemingly just cleaning up the contacts between the ignitor and coil eliminated the code 14.
However after clearing codes, I drive about 10 miles and code 25 comes right back.
I have attempted to get readings from the diagnostic port to see what is going on, first I get no reading from the ox1, then I attempted putting my analog meter between VF and VF1 with TE and TE1 jumped (engine warmed up and spinning 2500 RPM for this part), and no reading. Then I tried VF and VF1 with the meter and no reading either.
Does anyone have any suggestions as to what my problem is or what I am doing wrong?
I have checked as much of the vacuum lines as I possibly could, and can not hear any leaks or whistles either.
Thanks in advance for any insight you may be able to provide
-Trevor

scope103

Interesting. Where did you come up with hooking a meter between VF and VF1?

To check for conditioned (0- ~5v) Ox1 you look for voltage between VF and E1. http://personal.utulsa.edu/~nathan-b...42oxygense.pdf Of course, unconditioned Ox1 is from Ox1 to E1. Note that this is less than 1v; not many analog meters can give a usable reading that low, but give it a try.

It's very difficult to find vacuum leaks by ear, even big ones. You could try propane (an UNLIT torch) and listen for speed-up when you get close to the leak.

Last, there is no way to hook up a meter and get "no reading." You can get 0 ohms or 0.00volts or infinite resistance or 0.1ma, but you can't get "no reading." If you said you got "0.00 volts on the 19.99volt scale between VF and VF1," we might be able to figure out what was going on.

Good luck!

mischief2jz

Thanks for the input, appologies for the incorrect terminology, what i meant was 00.0 volts on the 0-10v setting between VF and E1, and also between VF and E1 (with E1 and T Jumped)
I tried at idle and at 2500 RPM
as far as the leak detection, I have tried the propane, and while the car was torn apart over this past summer I inspected all the lines, and I highly doubt there is a leak.

thanks again

scope103

"Lean" (excess oxygen) is low-voltage, so that could explain 0v on VF1. But not on Ox1; once warm the sensor doesn't go all the way to zero. I would suspect a broken wire (open connector, ...) in the oxygen sensor circuit. Ox1 on the diagnostic connector goes directly to the sensor. You could open the connector at the sensor and check it for continuityback to the diagnostic connector (though I would suspect the connector itself before the wiring.)

sactoyota

In most cases it is not the oxygen sensor at all. I had a code 25 and could not figure out what was going on. I did the tests above and couldn't get a reading other than lean, even though the truck ran great. The problem with trying to figure out code 25 is that it takes a couple days for the check engine light to come on again as the computer adjusts more to compensate until it is out of range. The only way I was able to figure mine out was by installing a air/fuel ratio meter onto the Ox diagnostic port. I changed my EGR, water temp sensor, and all injection equipment and it continued reading max lean.

Finally while messing around in the engine bay I bumped a vacuum line going to the VSV's and had a momentary rich reading on the meter. Started cliping the ends of vac lines to get fresh hose connections and all of a sudden the truck read perfect air/fuel ratios (bouncing back and forth between rich and lean). I had previously sprayed carb cleaner and starter fluid on all the hoses and had no signs of idle up indicating a leak, and there was no audible signs of an air leak. I never would have known I had found or fixed the problem unless I had the air/fuel ration meter hooked up to get instant results. I suggest that anyone with a code 25 use an air/fuel meter so you don't have to wait 4 days for the engine light to come on or stay off...

Co_94_PU

iTrader: (-1)

I'll second the loose or bad connection.

With the exhaust system warmed up, warm NOT hot, crawl under and do the resistance checks in the manual at the sensor. If you get eratic readings it's corrosion on the plug, spray some wd40 in both ends and wiggle the plugs together as you retattach them should clear it up. Best case senerio you cleaned something that didn't need it, worse case (eg, you used sand paper) you'll need to tighten the female(harness side) of the connector.

There is a diagnostic proceedure given in the manual to replicate and trigger the light. No need to wait weeks..

Here is the excerpt from the 22re. It'll be similar or identical for the 3vze, check the manual it's a few pages past the code list.
Your meter likely has a milli-volt setting use it to check for less than one volt (eg 0.45v = 450 milli volt). A good meter won't damage it's self if it gets the five volt input and a cheap meter who cares they're two dollars.


Start with the easy stuff..

Clean and reattach the main body ground next to the battery and the one for the head to firewall. Use a little wd40 when cleaning and before you rettach, it'll help clean off the corrosion and also prevent rust/oxide formation. (These are the first three on the "causes" list, IIRC, the E1 is connected to the passenger side apron, and the injectors thru the intake-head.)

Replace the fuel filter. Worst case you now have a spare.

Then the "usual suspects", or VisVersa

Perform the VAFM, and ECT tests.

*Addendum *
Some other code 25 threads
https://www.yotatech.com/forums/f116...e-25-a-262187/
https://www.yotatech.com/forums/f116...-3vz-e-258926/

As mentioned above(?), and other places. It could be as simple as a vacuum leak. A possible to overlook cause would be a malfunctioning PAIR valve. If defective you might be getting more fresh air introduced than it was designed for, or none at all. In addition to the "does it gurgle" FSM test, make sure it's sucking only not blowing indicating a stuck one way valve/flap.