Page 1 of 2 12 LastLast
Results 1 to 20 of 33

Thread: 4age smallport error code 25 and 26

  1. #1
    Join Date
    Jun 2012
    Location
    Nanaimo, BC
    Posts
    636

    4age smallport error code 25 and 26

    Trying to figure out what every possible cause of the 25/26 error code for my smallport. I've traced down a few small vacuum leaks which seems to have made it last longer before the check engine light comes back on but it still keeps coming on. The engine is freshly rebuilt with about 1200 km on it now. Brand new O2 sensor. Could it be injectors? I know I need to check my fuel pressure cause that is a possible cause for the codes. Just shoot any kind of ideas. I really want to get this thing running without the engine light coming on every day lol.

    Also it was a smallport swapped into an ae86 and I did the wiring myself but I really doubt it's the wiring cause it starts and runs perfect other than the check engine light coming on after a while of driving

  2. #2
    Join Date
    Feb 2011
    Location
    Kumamoto Japan
    Posts
    2,515
    You only have one O2 sensor? My AE92 used to have two, although the CEL was never on when it had one, it just failed E-tests...

    When I put it in the 86, the CEL never worked, I can't remember why, but there was a reason and it always ran fine too.

  3. #3
    Join Date
    Jun 2012
    Location
    Nanaimo, BC
    Posts
    636
    When I was wiring it up I used a single wire plug to connect my cel otherwise I would have to cut the wire if the harness ever had to come out. And ya. My engine harness only had wires for one O2 sensor. I'm leaning towards it still being a vacuum leak or fuel pressure. I'm gonna check that stuff out later when I'm off work

  4. #4
    Join Date
    Nov 2004
    Location
    Edmonton, Alberta
    Posts
    5,277
    AE92's only had two oxygen sensors on California cars. Canadian cars/other USA cars only had one.

    Jeff

    2011 GSE20 Lexus IS350 6MT F-Sport with LSD
    2005 NCP13 Toyota Yaris RS 5MT Hatchback
    1993 TCR10 Team Mondor Toyota Previa GT-S RM 5MT Studded Ice Race Van
    1986 AE86 Toyota Corolla GT-S 5MT Supercharged

  5. #5
    Join Date
    Nov 2012
    Location
    Brampton, Ontario
    Posts
    1,488
    What manifold did you use? The oxygen sensor could be too close/too far

    Also check the coolant temperature sensor (two wire for the ECU) - the fault detection logic for the oxygen sensor requires accurate CTS measurements.

    It's super weird that it throws both lean AND rich.

  6. #6
    Join Date
    Aug 2008
    Location
    London ON
    Posts
    1,621
    I've had that with a bad afm

    1991 Tercel 4A-GEsmallport RIP 09/02/2011 - - 1993 Supra.
    05 IS300 Daily

  7. #7
    Join Date
    Feb 2011
    Location
    Kumamoto Japan
    Posts
    2,515
    Wow, my car was from Cali?!? I didn't know that... I guess when I switched ECU's later, and broke the one off, that's why it didn't matter any more...

  8. #8
    Join Date
    Jun 2012
    Location
    Nanaimo, BC
    Posts
    636
    Bad afm. That's a good idea to look into. Are the smallport afm the same as others? I have a few lying around from bluetop motors. And sparky I will check into that coolant temp sensor.

    I have a RWD swapped smallport intake manifold. And obx header which never gave me any problems previously with my bluetop but that doesn't really mean it couldn't be a problem now

  9. #9
    Join Date
    Jun 2012
    Location
    Nanaimo, BC
    Posts
    636
    God damn lol. I thought I had it fixed cause I found a few more tiny vacuum leaks. And replaced all of my vacuum lines. Then while mildly puttering down the road today the damn cel came on again. I guess I will test my fuel pressure and afm next.
    Sparkie. Do you think that using solder to make all my connections on the wiring harness could be the problem?

  10. #10
    Join Date
    Nov 2012
    Location
    Brampton, Ontario
    Posts
    1,488
    Quote Originally Posted by jewbaka421 View Post
    Sparkie. Do you think that using solder to make all my connections on the wiring harness could be the problem?
    Nope, I do all my work with solder and heat shrink. The question is: did you do it well? sometimes these old toyota wires dont wet well and need extra heat and flux. did you extend a lot of wires or just power stuff?

  11. #11
    Join Date
    Jun 2012
    Location
    Nanaimo, BC
    Posts
    636
    I had to lengthen every wire at the ecu end to mount the ecu in the stock location. I would like to think I did a decent job of soldering all the connections. I used flux on every connection and the solder just seemed to melt into the wires pretty nice and even. It's gotta be fuel pressure or my afm or something simple.

    I used only original Toyota wire to lengthen everything as well. I got a hold of a spare smallport harness to chop out matching wire colours for every piece lol. It should be good
    Last edited by jewbaka421; 06-13-2016 at 07:47 AM.

  12. #12
    Join Date
    Nov 2012
    Location
    Brampton, Ontario
    Posts
    1,488
    Sounds good.

    Check that AFM first, it sounds more likely than CTS.

  13. #13
    Join Date
    May 2006
    Location
    Campbell River
    Posts
    3,156
    CTS will make it run fat but the computer thinks everything is good and it is just cold so should not throw a code.
    I've traced down a few small vacuum leaks which seems to have made it last longer
    Sounds like a bigger vacuum leak somewhere or some kind of added resistance in your O2 signal wire, maybe re-check the soldering job on that guy? Did you pull the plus to see if you can find one hole that is leaner than the rest? Might be a clue.
    1JZ 1984 Celica GTS
    1UZ 1981 Corolla sedan
    ? 1972 Celica race car

  14. #14
    Join Date
    Jun 2012
    Location
    Nanaimo, BC
    Posts
    636
    Did you mean pull the plugs clay? I haven't done that yet but I should see if it's one or all cylinders. Or if they all look fine maybe. I haven't doubled check the connections near the ecu yet cause it's all taped up and everything is back together. But I may have to open that end of things up and get rid of the solder and use the crimp connectors to be safe. I've gone over all my vacuum lines which aren't many. And I've checked all my air intake hoses and clamps. I even tried a bluetop afm today but that was an instant check engine light, unless I didn't leave the battery terminal off long enough to to reset the ecu. But it smelled extra gassy with that afm so I figured it's not compatible lol.
    My cousin also checked for vacuum leaks with some brake clean but that was only testing it at idle. Does anyone have a spare smallport afm? I will try to properly test mine tomorrow with a multimeter.

  15. #15
    Join Date
    Nov 2012
    Location
    Brampton, Ontario
    Posts
    1,488
    Brake cleaner (the chlorinated kind) doesnt burn, probably not the best leak detector.

  16. #16
    Join Date
    Jun 2012
    Location
    Nanaimo, BC
    Posts
    636
    I'm pretty sure it was non chlorinated brake cleaner. I could try again with something else that works better. Carb cleaner or something would prolly work good right?

  17. #17
    Join Date
    Sep 2015
    Location
    Chilliwack B.C.
    Posts
    12
    Have you measured the actual 02 sensor voltage? Some 4AGEs came with zirconia sensors and should read .1-.9 volts (low voltage being lean) while others came equipped with titania sensors and output a 1-5 volt signal (high voltage indicating a lean). Of course the sensor type has to match the ECU or you will have codes. Is it possible you were supplied the wrong part?

  18. #18
    Join Date
    Jun 2012
    Location
    Nanaimo, BC
    Posts
    636
    Highly possible. Lordco is the worst at getting the proper parts lol. That's a really good thought. Any idea how I can find out what type of sensor I require by part numbers on the ecu or something?

  19. #19
    Join Date
    Nov 2004
    Location
    Edmonton, Alberta
    Posts
    5,277
    The difference between the zirconia and titania sensors is actually not quite as Jimakire described. Zirconia generates a voltage between 0.1V and 0.9V depending on the AFR while titania sensors actually have a voltage applied to them and their resistance changes depending on AFR. For zirconia type sensors, the ECU simply reads the input voltage and uses it. For titania type sensors, the ECU reads the voltage drop between the supplied voltage and return voltage and calculates whether it is lean/rich depending on those conditions. For the 4A-GE/AE92 both sensors operate in the 0-1V range.

    The wiring is obviously different between the two types, zirconia sensors require 1 wire (generated voltage) to the ECU, while titania sensors require 2 wires (1V source from the ECU and signal wire back to ECU with a lower voltage). Additional wires will sometimes be added (heater circuit - 2 wires, or a ground wire instead of grounding to the exhaust - zirconia type only). The AE92 used these additional wires, resulting in 4-wire sensors for both types.

    All largeport 4A-GE's used zirconia sensors. Smallport 16V 4A-GE's used titania sensors on non-California models and continued using zirconia sensors on California models.

    It is definitely important that you have the correct type of sensor, if you have an AE92 smallport with only 1 sensor, it needs to be the titania type.

    Jeff

    2011 GSE20 Lexus IS350 6MT F-Sport with LSD
    2005 NCP13 Toyota Yaris RS 5MT Hatchback
    1993 TCR10 Team Mondor Toyota Previa GT-S RM 5MT Studded Ice Race Van
    1986 AE86 Toyota Corolla GT-S 5MT Supercharged

  20. #20
    Join Date
    Sep 2015
    Location
    Chilliwack B.C.
    Posts
    12
    Good info Jeff, I was going from memory and should have re-read my notes before commenting. Sorry for any confusion I may have caused.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •