Dewbro91

Ok I have had this problem for awhile and about ready to give up and sell this thing.
I have a code 25, but if I clear it, it takes about four days to show back up. Never at any specific speed or anything. I will just be driving and it comes on. I think I have fixed it and then it will just randomly come back on. Any help appreciated

abecedarian

The code means that the ECU has reached the end of it's ability to adjust the fuel mixture and the mixture is still too lean.

This could be caused by a faulty O2 sensor, exhaust leaks, intake / vacuum leaks, bad injectors, valve adjustments, throttle position sensor....

What have you done to fix the problem?

Dewbro91

I have no vacuum leaks. Every one is hooked up right. I did my AFM and my coolant temp. sensor. A few months back i had to take it to toyota and they said my valves were burned causing a miss on two cylinders. They replaced and reseated my valves. I did my O2 sensor last summer. Now that i think of it, could my misfire have fouled my new O2 sensor?

Dewbro91

I guess it would help to put what it is. Its a 1995 4runner V6 4x4

Flash319

Ya it sounds like your O2 may be cooked or it could be due to the conditions Abec stated. I would change the O2 first.
The reason it takes a few days is because the ECU remembers a base line condition. It will trim fuel (rich or lean) and then apply another offset using the O2 while driving. If the O2 is always reading too lean the base map will get shifted full rich and then when it tries to richen it out even more you will get a Lean Code.

If you warm your truck up and then stick a multi meter on volts and measure between E1 and OX1 on the diagnostic terminal under the hood you should see the O2 sensor jumping from .2ish to .7ish, up down, up down. If it is not getting up to .7 or .8 that means that the ECU can not get enough fuel in to get it rich OR the O2 sensor is no good.

O2 sensors usually fail this way. They just stop making enough voltage to show a rich condition.

Dewbro91

I just tested the volts between E1 and OX1 and it started at .003 and just kept going up from there. When I shut it off the last number was .012.. New O2 sensor Im guessing?

Flash319

I would say so. Not definate though because you will get this result also if ECU does not go into closed loop because of a bad temperature sensor or some other fault. Since your Temp sensor was changed I would change the O2 sensor and check again. I would also check the wiring to the O2 sensor, 2 of the wires are for the heater in the O2 sensor and that will also give a similar result if the heater is bad or the wiring.

Another way to test it is to warm up the engine. Short T terminal to E1. Then put the meter from E1 to VF and open the throttle a bit (throttle closed contact in the TPS must open). You should see the meter jump from 5V to 0 volts off and on. Much the same as taking the reading from the O2 itself but this is feedback from the ECU not the sensor. This just makes sure that the ECU is seeing the O2 sensor change.

Dewbro91

Well i just did my O2 sensor. Crossing my fingers. Ill post what happens in the next few days. Im just hoping it doesnt come down to cleaning my injectors..

ExcessFC

Whats the verdict?

Dewbro91

Well its been about a month and still no codes

FunkMaster88

Ive replaced my O2 sensor 2 time rebuilt the engine replaced all the seals, replaced the injectors, fuel filter, all my sensors, all my vacuum lines, my EGR and I still get a code 25 and no power or acceleration. I don't know what to do timing is spot on it idles good just no acceleration or power and i get a code 25, please help i don't want to spend an arm and a leg taking my truck to Toyota to get it looked at, no body works on Toyotas on the gulf coast.

akwheeler

If I had a dollar for every time I heard someone say the timing was spot on but it wasn't I'd be drinking for free tonight.
If I had a dollar for every time someone posted on a thread over 5 years old I'd buy a round for the house.
and if I had a dollar for every time someone neglected to include what kind of vehicle/engine/transmission they had I'd buy the bar.
If you have read any threads on this site regarding timing you will likely have seen mention of the harmonic balancer separating and no longer being an accurate mark for timing. put a straw down the spark plug hole for your #1 cylinder, or something long skinny and not likely to damage the piston or threads. then turn your crank shaft pulley with a wrench in the same direction that the engine spins when running and verify when the piston is at top dead center and that it is on the compression stroke (look at the valves or the cam timing marks or verify with a compression gauge. Then check your distributor rotor to see if it points at the #1 plug wire. From there you need a timing light and for those that find the engine won't start it is likely off by 180 degrees and needs to be verified that the #1 valves are closed.