CEL Code 25

[slosurfer]

So, I was on my way home last night at about 9:30 in the pouring rain when a CEL popped up. So I pulled over and checked everything, crawled underneath, etc. Was real fun in the rain. Everything looked good, gauges were good etc.. so I continued on home another 5 miles. Pulled the code this morning and got a code 25. Man, there is a big list of things that "could be" wrong! http://personal.utulsa.edu/~nathan-buchanan/93fsm/engine/85diagnosi.pdf
Cleared the code this afternoon, so I will see if it pops back up tomorrow. Oh and this is a 93 3.0 automatic 106,000 miles. The only thing I have noticed that has been wrong lately is that my gas gauge will sometimes take a dive and then slowly work its way back to its true level. Gas mileage has been about the same but hard to tell since I have been towing my trailer some for work. No noticeable change in idle or power. I hope it was just a fluke because I am working all weekend so not sure when I will get the time to do some diagnostics. The oxygen sensor is still the original, so I should definately diagnose that. Intake tubing looks good and all the vaccuum hoses seem to be on and in the right place. If it comes back on tomorrow, it looks like I have some work to do. Any suggestions would be appreciated.

[TDiddy]

Chris,
Most of those codes are multi-trip codes, meaning the code needs to be detected by the computer 2 or 3 times before the CEL light is actually activated. Don't expect it to come back on the first time you start it tomorrow. You'd think that if it was related to an injector, you'd aso be noticing a rough idle or power loss or something. I'd probably start with the O2 sensor first.

Good luck!

[slosurfer]

That's kind of what I thought, I took it for a test run tonight and it ran fine. Wasn't till a little while ago that I remembered the 2 trip thing, so I will see how tomorrow goes.

[MTL_4runner]

CEL code 25 => Air–Fuel Ratio Lean Malfunction

I just copied this stuff down to make it easier for people to find later.

Engine ground bolt loose
Open in E1 circuit
Open in injector circuit
Fuel line pressure (Injector blockage, etc. )
Open or short in heated oxygen sensor circuit (Common issue)
Heated oxygen sensor (Common issue)
Ignition system
Engine coolant temp. sensor
Volume air flow meter (Air intake)
ECM


I'd start by getting a new Denso O2 sensor from www.sparkplugs.com and try that first.

[slosurfer]

Thanks, I didn't have time to copy that over last night. CEL came back on today, hopefully tomorrow I have time to test some things.

[slosurfer]

Is it weird that this light will come and go? CEL came back on yesterday, but then last night it went off and stayed off. This morning on the way to work it came back on. I guess I assumed that it would only go off if it was "cleared".

[MTL_4runner]

If the O2 sensor was marginal the CEL may go on and off for a while until it stays on permanently.

[TDiddy]

That's what happened to me until mine finally gave out too.

[slosurfer]

Thanks, good to know. It did the same on and off thing today. I guess it is time to replace the sensor.

[slosurfer]

For those that want to test their Heated Oxygen Sensor.
http://personal.utulsa.edu/~nathan-buchanan/93fsm/engine/101heatedox.pdf

I only got the first part of the test done tonight and it passed. Although, it says it should be 68 degrees F so I may check it again tomorrow when it is warmer.

[MTL_4runner]

That's just the test for the heater element on the O2 sensor, I'd bet the O2 signal is the issue.

[slosurfer]

That's what I was thinking also, makes more sense being that it is a "come and go" type of problem. I didn't have anyone around to help me out last night except for my 2.5 yr. old son. I didn't think I could trust him to rev it up to 2500 rpm and keep it there, like is needed for the signal test.

Also, is there a difference between the Denso and NGK sensors? They both say they are oe replacements but one is a little cheaper. NOt that I care much about a ten dollar difference, just wondering if one was better than the other since I have heard good things about both companies when used in toyotas. I actually have the ngk iridium plugs that I got from sparkplugs.com

[MTL_4runner]

That's what I was thinking also, makes more sense being that it is a "come and go" type of problem. I didn't have anyone around to help me out last night except for my 2.5 yr. old son. I didn't think I could trust him to rev it up to 2500 rpm and keep it there, like is needed for the signal test.

Also, is there a difference between the Denso and NGK sensors? They both say they are oe replacements but one is a little cheaper. NOt that I care much about a ten dollar difference, just wondering if one was better than the other since I have heard good things about both companies when used in toyotas. I actually have the ngk iridium plugs that I got from sparkplugs.com


You need to get that little guy trained, mines 3 and I've got him handing me wrenches now....gas pedal is another story. :laugh:

NGK or Denso sensors should work fine, but I usually err towards Denso parts for my truck.

[slosurfer]

You need to get that little guy trained, mines 3 and I've got him handing me wrenches now....gas pedal is another story. :laugh:

NGK or Denso sensors should work fine, but I usually err towards Denso parts for my truck.


:lol: Ya, I can just imagine what my wife would say when she got home and found out I was using him to stand on the gas pedal for me. He has gotten pretty good at handing me stuff too, that's pretty cool when they help you out. Although all he wants to do is play with the air blow nozzle because it looks like a gun. :roll:

[reggie 00]

That's what I was thinking also, makes more sense being that it is a "come and go" type of problem. I didn't have anyone around to help me out last night except for my 2.5 yr. old son. I didn't think I could trust him to rev it up to 2500 rpm and keep it there, like is needed for the signal test.

Also, is there a difference between the Denso and NGK sensors? They both say they are oe replacements but one is a little cheaper. NOt that I care much about a ten dollar difference, just wondering if one was better than the other since I have heard good things about both companies when used in toyotas. I actually have the ngk iridium plugs that I got from sparkplugs.com


Ahh he could do it.

If you don't want to try why not use a piece of rubber or something and a pair of vice grips to lock the throttle cable in place?

[slosurfer]

Reggie, you read my mind.

We had some friends of ours lose their 2 yr. old son when he was playing in their van in the driveway and knocked it into neutral or something and it rolled down a hill killing him. So, we are not in too big of a hurry to get Jack anywhere near the drivers seat. Probably within the next year or so, he will start getting some "lessons" in the driver seat.

[reggie 00]

Reggie, you read my mind.

We had some friends of ours lose their 2 yr. old son when he was playing in their van in the driveway and knocked it into neutral or something and it rolled down a hill killing him. So, we are not in too big of a hurry to get Jack anywhere near the drivers seat. Probably within the next year or so, he will start getting some "lessons" in the driver seat.


sorry to hear about that.

definitely makes a good argument for that course of action.

he'll have plenty of seat time later im sure.

[slosurfer]

Yep, I think I could teach him now, but I will wait for his mother's sake.

[slosurfer]

That's just the test for the heater element on the O2 sensor, I'd bet the O2 signal is the issue.


Okay, this might be a stupid question, should I wait for the CEL to be on to do the test on the O2 signal? I ask because now it barely comes on, some days it comes on later in the day and the next morning goes off after driving a mile or so. I was going to test it today but thought it would be pointless if my CEL is off.

[MTL_4runner]

Okay, this might be a stupid question, should I wait for the CEL to be on to do the test on the O2 signal? I ask because now it barely comes on, some days it comes on later in the day and the next morning goes off after driving a mile or so. I was going to test it today but thought it would be pointless if my CEL is off.


You may have trouble testing it if the sensor is boarderline like that (may give a false reading). You could certainly test it with the CEL on or off (the ECU may be counting anyway). I honestly don't think I'd even bother wasting my time, I'd just replace it and reset the CEL myself.

[slosurfer]

That's what I was thinking. Maybe I will order a new set of sparkplug wires while I am at sparkplugs.com and tell my wife that they go together. LOL

[slosurfer]

I put in a new O2 sensor last night, so we will see how it goes. I used a direct OEM replacement NGK sensor from sparkplugs.com

[slosurfer]

Update: So far so good. No CEL anymore (although I probably just jinxed myself) :D

[Stevo3]

Update: So far so good. No CEL anymore (although I probably just jinxed myself) :D


Yep, thats usually how it works :hillbill: