Code 25

[Steveo]

I ran a diagnostic on my car five minutes ago and found it to throw a code 25. The heading describes that the code is "Air-Fuel ratio lean malfunction". Then shows things that could be wrong with my car. The list goes...

-Injector circuit
-Injector
-Fuel line pressure
-Air flow meter
-Air intake system
-Oxygen sensor circuit
-Oxygen sensor
-Ignition system
-Water temp sensor
-ECU

I was wondering if anyone who has had this code come up tell me what to do. Like what of all those things I should do first. Or if someone who hasn't had the code and just knows a lot about Supra's tell me in some kind of a order which would be easiest to start with and least expensive. Or should I get some money and take the car into a dealship tell them the code that came up and get them to start fixing the things that are wrong with the car. I would really like to avoid the last point as I would like to start working on my own car and attempt fixing things so I don't have to pay someone to do it for me.

Thanks Steven

[Dan_Gyoba]

Lean mixtures are nothing to sneeze at, they can cause nasty problems.

IIRC, this code only gets thrown when the ECU can't get a satisfactory reading fromt he O2 sensor after it's warmed up. (In closed loop mode.)

First things first. Is your O2 sensor wire harness connected properly?

If so, is the mixture actually lean? (A wideband on a dyno would test, but you don't want to do a real "pull" on a dyno if it's running lean!) If you can smell gas in the exhaust (Which you will when the ECU tries throwing as much fuel as it can into the mix) then chances are it's the O2 sensor.

It would still be an idea to have the injectors cleaned and tested.

[Steveo]

Alright then an O2 sensor is fairly cheap so if I just go ahead and change that it should help? I can't say I really want to throw it on a dyno just yet but if that will help me and in actuality save me money in the long run I am more then willing... I will try to take a sniff at the exhaust see what comes from that.

You probably wouldn't suggest it but that STP injector cleaner... Would it suffice or should I take them out of the car and bring them in?

I will have updates tomorrow as to what I had happen or what I did to the car.

Thanks Dan.

P.S Are there any shops in town that you would suggest?

[Dan_Gyoba]

I suppose that injecotr cleaner shouldn't HURT, but if the injectors are flowing so badly that it's causing a lean mixture, they've gotta come out of the car. They should be tested anyway.

I'm thinking of pulling my O2 sensor, too. I might try to clean it with a torch (Burn off any carbon deposits or the like) but I think that a replacement wouldn't be a bad idea.

I take my car to Wilson't Autotech on the west end. They've been good to me, but they're not cheap...

[Steveo]

Well I took a look at the car for a few mins this morning and saw nothing that looked like a O2 sensor... Would it be in somewhat of the same location on my 1G as it was on my 7M-GE? I found that one really easily. I tried taking a whiff of the exhaust but it smelt normal to me and didn't have the scent of gasoline. I called fuel injection plus and the only problem with them was I have to take the injectors out myself and bring them in. I am not car savy at all even though I am trying to get into it so taking the injectors out myself may be a problem as I cannot even locate them or find something on the net that can help me out...

So since I couldn't really smell any gas in my exhaust then it isn't the O2 sensor and I should waste my time finding it and changing it right?

[JimR]

Here are some pictures of the 1G. I believe the oxygen sensor is in the second picture... in the middle, near the bottom of the image.

http://movingtargetracing.com/~sfiggins/ga65/default.html (http://movingtargetracing.com/%7Esfiggins/ga65/default.html)

[Steveo]

Yes that would be the one Jim... I found it last night after looking on the net some more. When the engine is in the car it is hidden under the turbos and pretty much behind the heatshield... I have found a sensor on E-bay that will fit so I think I might order it once I get some money... I also booked my car in for an appointment at wilson's auto tech on monday to get my fuel system cleaned... With both of those things done I am hopeing my code 25 problem goes away.

[JimR]

Why not test your sensor and circuitry before you go out and buy a new one? It may not be the problem at all, and that would save you a lot of wasted time and money.

All you need is a voltmeter, and you don't have to disassemble anything. These instructions are for the 7M, but the diagnostic system and check connector should be identical:
http://cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=FI&P=119

[Steveo]

Well the one thing that was holding me back and to make me willing to just buy one was I didn't know how to do it. But now that you posted the link to the instructions I will probably get around it sometime this weekend. Thanks a lot. Probably just saved me a good 120 dollars...

[Steveo]

Well I unplugged my battery to wire some things then I plugged it back in and checked the codes again. To my surprise there was no codes on the car... Should I be worried and continue checking every time I drive the car hard? Or is my code 25 problem gone?

[JimR]

Do a little readin up on how that works over at the cygnusx1.net site, and post back up if you're still confused.