Engine codes

  1. Welcome to Toyota Tundra Forums : Tundra Solutions Forums General discussion forum for Toyota Trucks

    Welcome to Toyota Tundra Forums : Tundra Solutions Forums - a website dedicated to all things Toyota Tundra.

    You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, at no cost, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, Join Toyota Tundra Forums : Tundra Solutions Forums today!
     
Results 1 to 9 of 9

Thread: Engine codes

  1. #1
    Rookie
    Join Date
    Apr 2009
    Location
    Omaha, NE
    Posts
    12
    Liked
    0 times
    Rep Power
    0

    Default Engine codes

    i have a check engine light on and checked the codes today, i have 3 being thrown.
    1. p0128- i am guessing a new t-stat is all thats needed.
    2. p0420
    3. p0430
    i searched some of the previous threads about the 420/430 codes and am still a little concerned about how to properly diagnose which and how many of the four O2 sensors need replaced (if thats what i should be doing).
    any ideas if the combination of the 3 codes together should tell me something? the 4 cyl. HL has 108k on it, i have noticed reduced fuel milage, i used to get about 24mpg in town and 27-28 highway. now i get about 18 mpg in town and lucky to get 21 highway. it has orignal O2 sensors, any suggestions???
    thanks!

  2. Remove Advertisements
    Toyota Tundra Forum
    Advertisements
     

  3. #2
    Supporter LifeTech's Avatar
    Join Date
    Sep 2006
    Location
    NYC,NY
    Posts
    2,581
    Liked
    3 times
    Rep Power
    1490

    Default Re: Engine codes

    When yu Google /search for these codes what are they pointing to??

    Coolant Thermostat by itself won't trip a CEL.

    But, poor fuel economy can be attributed to improper engine operating temp. (T -stat fully stuck in open position) If never changed out before in 102k, it would be recommended to change out irregardless of your DTC's

    Original O2's as well as a dirty or faulty MAF sensor will contribute to poor economy as well. How is the idle? Steady at cold start as well as when warmed up? (OBDII in "Closed loop") .

    Clean your MAF sensor located just aft of the air box. Use Maf spray cleaner. CRC is one brand. Gently spray and allow to dry /evaporate... then reinstall . These are PM's that I do every so often when I change my Air filter.

    Get back.

    LT:happy:

  4. #3
    Rookie
    Join Date
    Apr 2009
    Location
    Omaha, NE
    Posts
    12
    Liked
    0 times
    Rep Power
    0
    Thread Starter

    Default Re: Engine codes

    hey LT, google tells me that i will be working on an O2 sensor, and that my coolant temp or temp sensor could be a contributor. (provided that i dont have any other exhaust leaks) i will clean the MAF, the idle seems perfect, cold, warm, it doesnt seem that the idle is effected...
    i wont buy four new O2 sensors until you tell me to pull the $$$$ trigger, lets hope we arent buying all four????

  5. #4
    Supporter LifeTech's Avatar
    Join Date
    Sep 2006
    Location
    NYC,NY
    Posts
    2,581
    Liked
    3 times
    Rep Power
    1490

    Default Re: Engine codes

    Do yu have a 4 cylinder???

    If so ...yu only have Two (2) O2 sensors. One at the exhaust mainifold and one at the Cat Conv. ( They are different part numbers.) One is a "heated" O2 sensor. Usually the one at or just before the Cat. The other is on the exhaust manifold engine pipe. (closest to the engine front)
    (Only the 6 cyl engines have 4 of them.)

    Another member bepperb, posted this diagram. He has the 4 cyl. engine.

    Bad Oxygen Sensor ?

    This should help very much in your situation.. But yu need to know which bank # as well as O2 sensor # the code is referring to.

    The codes should point to which it should be. Yu can change both as a PM since they have over 100 k them. But is optional. Just changing out the correct faulty one is fine if $$$ is tight.

    Autozone will lend you a special socket for removal for free I believe. Use "PB Blaster Spray" on them and let soak for a while.
    Hope this helps.

    LT:happy:
    Last edited by LifeTech; 04-10-2009 at 05:24 AM. Reason: spel

  6. #5
    Rookie
    Join Date
    Apr 2009
    Location
    Omaha, NE
    Posts
    12
    Liked
    0 times
    Rep Power
    0
    Thread Starter

    Default Re: Engine codes

    thanks again LT. i will get back and verify whether i have 2 or 4 O2 sensors, my haynes manual says 2003 and earlier 4cly engines have 2 upstream, and the same manual states that 2001-2003 4cyl engines will also have 2 downstream. i will be cleaning the MAF, throttle body, and changing the t-stat today. when i do i will locate all O2's and verify how many we have. it is a 2002 4 cyl.
    IF after the work i do today still allows a code to be thrown, my major concern is the fuel efficiency and operation. i know the upstreams help to adjust the air fuel ratio, which i want to make sure isnt comprimised for efficiency. but i dont want really want to spend $700 to find out that the cat is bad, and the money spent didnt improve the mileage- if i can narrow it down to a cat, i am not planning on doing that any time soon because of the cost. i just want her to keep purring! i will post later with some more info. thanks again!

  7. #6
    Junior Member
    Join Date
    Jul 2007
    Location
    Milwaukee, WI
    Posts
    296
    Liked
    1 times
    Rep Power
    8

    Default Re: Engine codes

    I know nothing of the P0128 code. Coolant temp too low? I'd start with a new thermostat, if for no other reason that it's probably less than 10 bucks and the most likely culprit. Of course, it could also be the sensor that reads the coolant temp. How is the temp gauge on your dash? Goes to 8o'clock within a few miles and stays like it's supposed to? Reduced fuel mileage would be the case if the engine isn't getting to full temp.

    Apparently the pre-04 4cyl Highlanders have four O2 sensors. I don't have one, or a manual, so I don't know. But the 420 codes are tricky. A lot of places will blame the cat, but what it's basically saying is that the downstream o2 sensor is giving a reading that would indicate that somthing isn't working correctly. Could be the MAF, upstream o2, cat or maybe the downstream is reading incorrectly. Does your exhaust smell bad, like rotten eggs?

    If you're going into this trying to throw parts at it, at least start cheap. First do the thermostat, then cleaning the MAF is free, and I'd put new plugs in if they're old, and a bottle of Techron or BG44K in the fuel. Get the codes reset, and see what comes up. If it's the 420/430 again, maybe search around Camry forums and see what people have been doing. 2 heated and 2 regular o2's are probably 500 bucks total.

    I guess it's also worth mention... the downstream o2 just checks the exhaust. The computer doesn't use it to calculate air/fuel ratio, only the upstream. So if you really think your mileage is down and it's not just winter gas and cold weather, then I guess that would point to the upstream cats possibly throwing off the a/f ratio.

  8. #7
    Supporter LifeTech's Avatar
    Join Date
    Sep 2006
    Location
    NYC,NY
    Posts
    2,581
    Liked
    3 times
    Rep Power
    1490

    Default Re: Engine codes

    bepperb pretty much covered it well I might say.

    Let us know the outcome.

    Good luck

    LT

  9. #8
    Rookie
    Join Date
    Apr 2009
    Location
    Omaha, NE
    Posts
    12
    Liked
    0 times
    Rep Power
    0
    Thread Starter

    Default Re: Engine codes

    to answer bepperp and lifetechs questions, the idle is good and normal, cold and warmed. there hasnt been any rotten egg smell indicating a bad cat, the engine warms and gets to operating temp normally, and stays good the whole time while driving. basically all i've done so far was cleaned the MAF sensor, throttle boby, tightened a clamp on the airbox that i found a little loose. disconnected my battery (was going to do t-stat but didnt have time) for 30 mins, hooked it back up and have had my milage improve to what it used to be. i have driven 600 miles since, and everything seems great, milage is back and no codes have re-appeared.
    i also did some maitenance on contributing factors that i am sure added to the milage improvement:

    new tires- General HT Grabbers, stock size 225/70/16

    changed the conventional eng oil to mobil1 full synth.

    changed the rear diff and frt. diff/ tranfer case to mobil1 full synth.

    changed tranny fluid, routine "pm", toyota t-4 fluid.

    i can actually feel less drag while driving down the road after the fluid changes, and tires....So for now everything is okay, but that doesnt mean that a t-stat and O2 sensors wont get changed just for mileage thats on them. if anything changes i will update, and a huge thanks to both lifetech and bepperp!!!!!!!! thank you guys!!! i really appreciate the help.

  10. #9
    Junior Member
    Join Date
    Oct 2006
    Location
    Austin, TX
    Age
    40
    Posts
    481
    Liked
    3 times
    Rep Power
    8

    Default Re: Engine codes

    O2s last 8yr/80K miles. You are long overdue to change the O2 sensors. Remember the P0420/P0430 are the related to emissions and quite hard to root cause since O2s, MAF and bad pre-cat/cat are all mapped to these codes.

    Change the O2s and they will go away and offcourse u will get better MPG.

    Get O2s from www.ngk.com

    Good luck.

Posting Permissions

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