22REFORME

88 4runner 22re

truck ran good with no codes, then after 290k or so the motor gave up(head gasket or cracked head not sure) so i had the engine replaced and ever since then i have had code 25 O2 sensor. I just put a brand new sensor in and i am still getting the code. anyone break it down for me? what should i be checking?

thanks so much in advance, since this truck doesn't seem to be selling it looks like may be driving home across the country so i would like the code off by then

MudHippy

Did you use a new gasket when you installed the new O2 sensor? If not, that'll cause that.

22REFORME

ahh.. no i didn't. ok guess i'll replace the gasket. though it seems tight. also the light came on after the engine swap.

MudHippy

Well, that's what it was causing mine. New gasket solved it.

The FSM has a check list too.
http://personal.utulsa.edu/~nathan-b...26diagnosi.pdf

I'd do a new gasket first, and if that don't fix it, check the wire for shorts/loose connections/corroded terminals.

22REFORME

well it threw the code when the new engine was installed so i gotta think it was originally thrown by something other than the gasket and the wiring is fine i checked it when i replaced the sensor.

MudHippy

I can see your line of reasoning there. Anyways the gasket ain't a bad idea, might help to prevent it popping up some time later. Cheap too.

But, if your interested in pursuing other possible causes, the FSM is the best place to start for info on how/where to.

See the Engine/22RE/MFI System/Diagnostics section and go from there.

http://personal.utulsa.edu/~nathan-buchanan/93fsm/

You did clear the code after you installed the new sensor right? It's gonna stay stored and keep showing it untill you do. The code won't go away on it's own I mean. Even if you did solve it with the new sensor.

22REFORME

yes i cleared the code..

22REFORME

not sure if it matters or not but at idle the light is not on and as soon as i hit something like 2-2.5rpms it throws the light.

MudHippy

Hmmm, that's pretty much what mine did when the gasket was leaking. But that's just anecdotal evidence. Doesn't necessarily mean it couldn't be something else causing it to do that.

I dunno, but I'm plumb out of suggestions at this point.

Good luck!

22REFORME

anyone?

87 'runner boosted

i think i have the same problem...havent checked codes or nothin yet, just started last night, cel came on while driving home engine running around the 3k rpm mark...22re with extremely low power issues.

22REFORME

shop replaced my cat and o2 sensor today.. light still on! aarrch

87 'runner boosted

I checked under my hood the other day, O2 sensor wiring is broken off at the sensor. Going to get another sensor soon and replace it...doubt it will fix my low power issue though...and my cat will definitely be rodded out soon.

sam333

I and many others have had problems with non-oem( not original) 02 sensor( denso is the best).

A very common problem is air leaking into your exhast ahead of the o2 sensor( like MudHippy sugested the gasket) , but it can be anywhere ahead of the sensor also.
If you can get a shop vac and turn it on blow, hook the hose up to your tail pipe( duct tape).Use soapy water in a spray bottle to find leaks in your exhast( the escaping air will form bubbles that you will easily be able to see.

Its also very easy to contaminate the sensor with anything that you find in an engine( oil, grease,antifreeze, silicone from sealants.

You can test the 02 sensor yourself, you just need analog volt meter, jumper wire , manual , and tach if dont have one in the truck.

Beyond the testing in the manual, you can make the fuel/air mixture rich or lean( add propane or vacuum leak) and then check the o2 sensor for the proper voltage( voltage will fluctuate depending on rich or lean).

There are more tests and I can give more detail if you think you can do them yourself, or there is alot of info on the web about o2 sensors and trouble shooting them.

87 'runner boosted

O2 sensor wont cause a low power issue though correct?

sam333

If everthing else is working properly no . If your 02 sesor is bad or disconected the computer will go into the default setting, pre programed fuel settings ( open loop ) your emissions will be a little worse though.

22REFORME

the shop wants me to come back monday so they can look for a pinched wire, i don't think there is a pinched wire.

22REFORME

ok so the latest news from the shop is that my ecu is bad. they say that the engine is running clean and with the right fuel maps and all so the computer is throwing a false code. does this sound right?

MudHippy

The part about the ECM throwing a false code maybe.

The rest of it doesn't sound right at all.

There's no real way to determine if the fuel maps are right. One could make educated guesses that they are, but that's all on an OBDI system.

They may have attatched an A/F ratio meter/gauge, or simply a voltmeter, to the O2 sensor circuit to make a more accurate analysis of it's functionality. Which may have led them to believe that it's not the problem. And that may have also given them enough information to estimate that the fuel maps are "right".

"Running clean" makes little sense either. What exactly is that supposed to mean? Do they mean it'll pass a smog inspection? And what good does knowing that get you, as far as trying to figure out why the engine's computer thinks it's running lean? I'll go ahead and clue you in, it means nothing/doesn't tell you anything regarding that.

Bottom line is this, they're not going to be able to figure it out any better than you can. The FSM is going to be the best source of information on troubleshooting the various systems that could be causing the issue. All you need to do is go through the list of them provided in the diagnostics section(post #4, and below) and check that they are functioning correctly. It tells you where to look for the problem by stating their names and the FSM page numbers for details on how to check some of those systems or components. The rest of them are detailed in other parts of the FSM, with procedures on how to check those too.

Systems/components that are suspect:
Engine ground bolt loose
Open in E1 circuit
Open in injector circuit
Fuel line pressure (Injector blockage, etc.)
Open or short in oxygen sensor circuit
Oxygen sensor
Ignition system
Engine coolant temp. sensor
Volume air flow meter (Air intake)
ECM

FSM pages where more information on how to check some of those are found:
EG1–138
EG1–156
EG1–174
EG1–136
EG1–154
EG1–172

FSM pages on diagnostics:
http://personal.utulsa.edu/~nathan-b...26diagnosi.pdf

FSM pages on troubleshooting
http://personal.utulsa.edu/~nathan-b...27troubles.pdf

The FSM engine section where you'll find the pages with info on all of the engine management systems:
http://personal.utulsa.edu/~nathan-b...sm/engine.html

The entire FSM for reference:
http://personal.utulsa.edu/~nathan-buchanan/93fsm/

Tools required to check the various suspect systems/components:
Multimeter, or an Ohmmeter and a Voltmeter
Fuel pressure gauge, requires an SST, or the installation of a schrader valve in a fuel rail to use a standard type.

It's not as hard as it sounds. And unless you're willing to spend $500+ on a new ECM, not really knowing for sure if that's even going to fix it, then it's worth looking into IMO. EVERYTHING else on the list should be checked first. The ECM is not only the most expensive part to replace, it's the LEAST likely to be the actual cause. That's why the ECM is at the bottom of that list.

BTW, did you check any of the things sam333 suggested? It's not a Bosch or no-name/generic O2 sensor is it? If it's not a Denso, or OEM, then there's your problem. You never did say that you made sure that a new gasket was used either. Well, is there one on there now? If not then this has been a colossal waste of everybody's time, because that's still most likely to be the cause. And if someone talked you into replacing the cat to try and solve it, they lied BIG TIME! A malfunctioning cat will not affect the A/F ratio PERIOD. I'd take it back and ask for a refund if I were you.

22REFORME

well it turned out that the cat that was on the truck had been gutted, so replacing the cat was good either way. this shop installed a new denso O2 with new gasket. i don't think they have taken the time to go through all of the troubleshooting. i am on the road and do not have any of my tools with me, so i am at the mercy of these shops somewhat.