How, EXACTLY, does the ECU work?

  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!
     
Page 1 of 2 12 LastLast
Results 1 to 15 of 19

Thread: How, EXACTLY, does the ECU work?

  1. #1
    Junior Member
    Join Date
    Nov 2003
    Location
    Los Angeles, CA
    Posts
    77
    Liked
    0 times
    Rep Power
    11

    Default How, EXACTLY, does the ECU work?

    I've read that the ECU adjusts based upon a person's driving style. How exactly does it adjust? Does it only adjust the air-fuel mixture? Does it also adjust the ignition timing? Does it only remember the past copule of hundred miles, or does adjust based upon all cumulative data input from day one? Does it adjust the transmission's shifting characterisitcs? (I.E shift points and how hard it shifts) How does one's driving style really affect the adjustments? Will driving the truck hard mean that the ECU will then calibrate to generate the most horsepower and torque when the truck is driven hard? Does resetting the ECU after a mod really accomplish anything in the long run, or will the results be the same without resetting after a few hundred miles anyway? Sorry for all the questions, but the workings of the ECU are a mystery to me. Thanks in advance for any replies.

  2. Remove Advertisements
    Toyota Tundra Forum
    Advertisements
     

  3. #2
    Guest
    Join Date
    Feb 2003
    Location
    Henderson, NV
    Posts
    5,988
    Liked
    33 times
    Rep Power
    0

    Default

    The ECU "learns" about your engine as you drive the car. The "learning" is actually a process that the ECU uses to track the tolerance changes of the sensors and actuators on the engine. Two examples of these values are the position of the idle-air bypass valve (automatic choke) at idle with the A/C on, and the trim gain on the injectors. The ECU stores these "learned" values in battery backed-up RAM so that it doesn't have to start from scratch the next time you turn your engine over.
    "Resetting the ECU" is the process of clearing all the long term memory from the ECU's memory. These variables trim idle speed, fuel, spark, and more. The ECU will also store trouble codes for diagnostic capability. By resetting the ECU, the trim values will be set to some neutral default value and all of the trouble codes will be cleared.
    How-To

    To "reset" the ECU, all you have to do is remove the source of backup power. To keep the memory alive while the car is off, the ECU has a direct line, through a fuse, that goes right to the battery. This is usually the same line and fuse that supplies backup power to your radio so it doesn't forget all of its settings. Your ECU has now lost all of its long term memory values and will "reset" them all to defaults when it next powers on. By the way, the factory radio's memory lasts for a minute or two, so you probably will not lose your saved stations.
    Myth

    There is quite a bit of mythology revolving around resetting the ECU. Many people mistakenly believe that they need to reset the ECU after installing major engine modifications. Others believe resetting will resolve engine problems. Neither are correct.
    Reality

    The ECU is always tracking the engine's sensors and actuators. Resetting the ECU does not cause the ECU to learn engine changes any faster. The ECU is always tracking the gradual changes in the engine sensors and actuators. The ECU never gets satisfied with a setting, and is always updating the trim values. It will discover whatever change you made to your engine and make the appropriate changes. In fact, unplugging the ECU will most likely increase the learning curve of the new part.
    There are only two reasons why you would want to reset your ECU. One is to clear a CHECK ENGINE light or error code after fixing the problem that caused the error. The other is to reset the spark advance trim value. The advance trim controls how much the timing is retarded from what the factory engineers considered optimum. This particular trim value is the only one the ECU "resets" to a non-neutral MAX value. If you are driving on low grade gas, the pinging picked up by the knock sensor causes this trim value to be lowered, and your timing to be retarded. If you go to the track and put good gas in the tank, you might not want to wait for the ECU to learn about the new gas and advance the timing. So resetting the ECU in this case makes sense. However, in the process, you will lose your idle and fuel trims (probably not too important for drag racing, though).
    Questions

    Won't clearing the trouble codes make the car run better? If the ECU notices a problem with a sensor, it will flag a code and possibly turn on the CHECK ENGINE light. Should the problem go away, the ECU will turn off the light and start using the sensor as normal once again. The code will be stored inside for later diagnostic retrieval. But that code being stored does not affect the ECU operation in any way.
    I reset the ECU, and now the car runs rough! Why? The engine may run rough or idle poorly right after ECU reset. The ECU now has default numbers in its trim memory - it has to adjust them to match the tune of your engine and its sensors and actuators. It might take a day or two of driving in traffic before the engine will settle down again. Now you know why the ECU remembers these values in the first place!

    Here is another good site for more detailed INFO
    http://auto.howstuffworks.com/car-computer1.htm
    Hope this helps

  4. #3
    Junior Member
    Join Date
    Nov 2003
    Location
    Los Angeles, CA
    Posts
    77
    Liked
    0 times
    Rep Power
    11
    Thread Starter

    Default

    Thanks for the explanation mustang 67408. As a follow up, I recently put a Magnaflow muffler on (no other mods). I drove the truck for about 100 miles before resetting the ECU. I could swear that my truck pulled harder at full throttle after the reset. If in fact the truck does perform better after the reset, does this mean that the default settings are providing more power than my learned settings? Will my settings eventually adjust back to the "pre-reset" settings anyway? If so, after how many miles will this occur? Thanks in advance for any replies.

  5. #4
    Guest
    Join Date
    Feb 2003
    Location
    Henderson, NV
    Posts
    5,988
    Liked
    33 times
    Rep Power
    0

    Default

    Quote Originally Posted by gnlw
    Thanks for the explanation mustang 67408. As a follow up, I recently put a Magnaflow muffler on (no other mods). I drove the truck for about 100 miles before resetting the ECU. I could swear that my truck pulled harder at full throttle after the reset. If in fact the truck does perform better after the reset, does this mean that the default settings are providing more power than my learned settings? Will my settings eventually adjust back to the "pre-reset" settings anyway? If so, after how many miles will this occur? Thanks in advance for any replies.
    My own personal opinion is "YES" the ECU will revert back to its pre-set settings after a week or so of driving. The initial pulling your felt may diminish after some time.
    You havent changed anything electrcial about the ECU so it doesnt know about the muffler. The ECU has perameters progammed into it for a specific exh size designed by Toyota, if you changed this things may feel better for a while, but the ECU is going to try to adjust everything back to its Programmed perameters.
    Many people have tried adding RESISTORS to the MAF to "TRICK" the ECU into thinking the truck is running cooler than it really is, this is supposed to richen the mixture and produce more power, but from what I have heard and read, the ECU is smarter than this and after a week or so relearns things and makes everything go back to its initial programming and targets.
    I think you need to have another ECU that is programmable or adjustable to actually make more HP and TQ.
    Toyota did their homework on these trucks and personnally I dont feel there is much more to extract from them. They are great just the way they are.
    S/Cing is a whole nother ballgame.
    Just my opinion
    Others may know more and share with you.

  6. #5
    Junior Member
    Join Date
    Nov 2003
    Location
    Los Angeles, CA
    Posts
    77
    Liked
    0 times
    Rep Power
    11
    Thread Starter

    Default

    Thanks again mustang67408. I've also heard about long term maps and short term maps. Can you explain how they work? How long does it really take for the ECU to create a long term map, etc. Thanks in advance for any replies. Any other responses from the other tech experts would also be appreciated.

  7. #6
    Guest
    Join Date
    Feb 2003
    Location
    Henderson, NV
    Posts
    5,988
    Liked
    33 times
    Rep Power
    0

    Default

    Feedback from the 02 or A/F sensor(s) influence short term fuel trim and then in turn short term fuel trim influences long term fuel trim.
    Short term values are not stored in memory and are lost when the ignition is turned off. Long term values are stored in memory, because they are part of the basic injection duration. Long term values affect injection duration in OPEN and CLOSED loop because they are used to calculate basic injection duration
    It is important to remember that ACTUAL fuel trim is opposite of the actual DTC code stored.
    A system to lean with code of P0171 will mean the ecu is making a RICH correction.

    FUEL TRIM:
    As things change over time the ECU needs a way to adjust the injection duration and improve drivability and emmisions performance. Fuel Trim is a program in the ECU designed to compensate for these changes.
    Fuel trim allows the ECU to LEARN and adjust the injection time quickly back to "NORMAL"
    SHORT TERM FUEL: Instant responce and correction
    SHort FT is based on the 02/-A/F sensors and therefore only functions in closed loop. SHort FT responds rapidly to changes in the O2-A/F. If Short FT is varying close to 0% little or no correction is needed. When SHORT FT is positive, the ECU has added fuel by increasing injection duration. A negative% means it is subtracting fuel by decreasing duration.
    The SHORT FT value is a TEMPORARY value and not stored.
    SHORT TERM FT is used to modify LONG TERM FUEL TRIM. When the SHORT FT remiains HIGHER or LOWER than expected, the ECU will add or subtract this from the LONG TERM VALUE.
    SHORT TERM FT is a temporary addition or subtraction of fuel to basic injection duration


    LONG TERM FUEL:
    Long FT is stored in memory because it is part of the basic injection duration calculation. The ECU uses the SHORT FT to modify the LONG FT
    Long FT does not react rapidly to sudden changes, it only changes when the ECU decides to use the SHORT FT value to modify it. It is run in open and closed loop and is stored in memory.
    A positive % indicates the ECU is adding fuel and a negative% indicates its removing fuel.
    LONG TERM FT is part of basic fuel trim and stored in memory as a guideline.

  8. #7
    Junior Member
    Join Date
    Nov 2003
    Location
    Los Angeles, CA
    Posts
    77
    Liked
    0 times
    Rep Power
    11
    Thread Starter

    Default

    Thanks again for the info mustang67408.

  9. #8
    Guest
    Join Date
    Feb 2003
    Location
    Henderson, NV
    Posts
    5,988
    Liked
    33 times
    Rep Power
    0

    Default

    Your Welcome and HAPPY HOLIDAYS

  10. #9
    Supercharged Member
    Join Date
    Aug 2007
    Location
    DEERFIELD BEACH
    Posts
    3,814
    Liked
    19 times
    Rep Power
    2910

    Default Re: How, EXACTLY, does the ECU work?

    hi, so how long does it take for your ecu to learn?
    and what if you don't disconnect the battery while doing a mod?
    50 miles, 1, 2 ,3 ,tanks of gas?
    or is it always learning.
    regards,
    gorilla

  11. #10
    Veteran Member bigMoney's Avatar
    Join Date
    Nov 2009
    Location
    Greenville, SC
    Posts
    1,081
    Liked
    170 times
    Rep Power
    85559

    Default Re: How, EXACTLY, does the ECU work?

    Quote Originally Posted by mustang67408 View Post
    The ECU "learns" about your engine as you drive the car. The "learning" is actually a process that the ECU uses to track the tolerance changes of the sensors and actuators on the engine. Two examples of these values are the position of the idle-air bypass valve (automatic choke) at idle with the A/C on, and the trim gain on the injectors. The ECU stores these "learned" values in battery backed-up RAM so that it doesn't have to start from scratch the next time you turn your engine over.
    "Resetting the ECU" is the process of clearing all the long term memory from the ECU's memory. These variables trim idle speed, fuel, spark, and more. The ECU will also store trouble codes for diagnostic capability. By resetting the ECU, the trim values will be set to some neutral default value and all of the trouble codes will be cleared.
    How-To

    To "reset" the ECU, all you have to do is remove the source of backup power. To keep the memory alive while the car is off, the ECU has a direct line, through a fuse, that goes right to the battery. This is usually the same line and fuse that supplies backup power to your radio so it doesn't forget all of its settings. Your ECU has now lost all of its long term memory values and will "reset" them all to defaults when it next powers on. By the way, the factory radio's memory lasts for a minute or two, so you probably will not lose your saved stations.
    Myth

    There is quite a bit of mythology revolving around resetting the ECU. Many people mistakenly believe that they need to reset the ECU after installing major engine modifications. Others believe resetting will resolve engine problems. Neither are correct.
    Reality

    The ECU is always tracking the engine's sensors and actuators. Resetting the ECU does not cause the ECU to learn engine changes any faster. The ECU is always tracking the gradual changes in the engine sensors and actuators. The ECU never gets satisfied with a setting, and is always updating the trim values. It will discover whatever change you made to your engine and make the appropriate changes. In fact, unplugging the ECU will most likely increase the learning curve of the new part.
    There are only two reasons why you would want to reset your ECU. One is to clear a CHECK ENGINE light or error code after fixing the problem that caused the error. The other is to reset the spark advance trim value. The advance trim controls how much the timing is retarded from what the factory engineers considered optimum. This particular trim value is the only one the ECU "resets" to a non-neutral MAX value. If you are driving on low grade gas, the pinging picked up by the knock sensor causes this trim value to be lowered, and your timing to be retarded. If you go to the track and put good gas in the tank, you might not want to wait for the ECU to learn about the new gas and advance the timing. So resetting the ECU in this case makes sense. However, in the process, you will lose your idle and fuel trims (probably not too important for drag racing, though).
    Questions

    Won't clearing the trouble codes make the car run better? If the ECU notices a problem with a sensor, it will flag a code and possibly turn on the CHECK ENGINE light. Should the problem go away, the ECU will turn off the light and start using the sensor as normal once again. The code will be stored inside for later diagnostic retrieval. But that code being stored does not affect the ECU operation in any way.
    I reset the ECU, and now the car runs rough! Why? The engine may run rough or idle poorly right after ECU reset. The ECU now has default numbers in its trim memory - it has to adjust them to match the tune of your engine and its sensors and actuators. It might take a day or two of driving in traffic before the engine will settle down again. Now you know why the ECU remembers these values in the first place!

    Here is another good site for more detailed INFO
    HowStuffWorks "How Car Computers Work"
    Hope this helps
    Nice write up. Thanks, but a question, if I've had the dealer make some changes, i.e., turn off seat belt chime, etc, will those be lost with a batt disconnect or are they written to non-volative RAM on the ECU?
    >>big$$

    ========================================
    SR5 Dbl Cab 2009, 4x4, 5.7L, Flex Fuel, Desert Sand Mica, Tow Pkg, Cold Pkg, Ventashades, Bugflector II, AMP Bumper Step, OEM All weather mats, Line-X, OEM Chrome Running Bds, Underseat Rear Storage, OEM Sill Protectors, Chrome Tailgate edges, Chrome Lic Plate Frame, aFe Pro Dry-S Air Cleaner, Charcoal Air Filter Mod; Visor Labels Mod; Fog Lights Mod; DRL Off Mod; Extra Loud Horn Mod, OEM SS Exhaust Tip
    "We still find the greedy hand of government thrusting itself into every corner and crevice of industry and grasping at the spoils of the multitude." - Thomas Paine (1737-1809) Patriot
    "The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government." - Thomas Jefferson (1743-1826) U. S. President

  12. #11
    Senior Contributor tundrunk's Avatar
    Join Date
    Nov 2009
    Location
    check the bar or liquor store
    Posts
    5,854
    Liked
    1994 times
    Images
    216
    Rep Power
    241860

    Default Re: How, EXACTLY, does the ECU work?

    Best info I have seen in quite some time, points sent.

    I have a question for you(see what happens when you give good answers!). What is this open loop/closed loop I have heard about? I get the image in my head of a parallel circuit or a series circuit when I have read these terms, but nobody has ever explained them.
    “Life should not be a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside in a cloud of smoke, thoroughly used up, totally worn out, and loudly proclaiming "Wow! What a Ride!”
    ― Hunter S. Thompson

  13. #12
    Guest
    Join Date
    Feb 2003
    Location
    Henderson, NV
    Posts
    5,988
    Liked
    33 times
    Rep Power
    0

    Default Re: How, EXACTLY, does the ECU work?

    Quote Originally Posted by bigMoney View Post
    Nice write up. Thanks, but a question, if I've had the dealer make some changes, i.e., turn off seat belt chime, etc, will those be lost with a batt disconnect or are they written to non-volative RAM on the ECU?
    No they wont be lost. The seatbelt chime in a Tundra that is able to be switched off is stored in the Combination meter ECU, so if the combination meter is unplugged then the seatbelt chime will be reset, but disconnecting the battery should not reset it.

    Quote Originally Posted by tundrunk;
    What is this open loop/closed loop I have heard about? I get the image in my head of a parallel circuit or a series circuit when I have read these terms, but nobody has ever explained them.
    ECU Modes:

    OPEN LOOP - this is the mode your ECU is in until the coolant temperature and a couple other sensors get to operating values. This is also true when you are at WOT or when throwing codes/ CEL's

    CLOSED LOOP - the ecu uses information primarily from the Oxygen Sensor and adjusts fuel delivery and timing to achieve minimum emmisions, better gas mileage and power

  14. #13
    Senior Contributor tundrunk's Avatar
    Join Date
    Nov 2009
    Location
    check the bar or liquor store
    Posts
    5,854
    Liked
    1994 times
    Images
    216
    Rep Power
    241860

    Default Re: How, EXACTLY, does the ECU work?

    Hey, that was pretty quick, thanks.
    “Life should not be a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside in a cloud of smoke, thoroughly used up, totally worn out, and loudly proclaiming "Wow! What a Ride!”
    ― Hunter S. Thompson

  15. #14
    Rookie
    Join Date
    Aug 2011
    Location
    Neenah, WI
    Posts
    11
    Liked
    0 times
    Rep Power
    0

    Default Re: How, EXACTLY, does the ECU work?

    Okay...so digging up and old thread here since this Mustang guy seems to know what he's talking about.

    This may be an oprinion thing, but is it worth resetting the ECU after purchasing a used truck? My 07 I just got has 21k on it, and I obviously would have no idea how the previous owner drove it (aside from infrequently). Would resetting the ECU have any benefit to wiping out all the data/habits from his driving style, or do you think that over the next little while it will sort of work things out on its own?

  16. #15
    Guest
    Join Date
    Feb 2003
    Location
    Henderson, NV
    Posts
    5,988
    Liked
    33 times
    Rep Power
    0

    Default Re: How, EXACTLY, does the ECU work?

    Quote Originally Posted by SmurfTruck View Post
    Okay...so digging up and old thread here since this Mustang guy seems to know what he's talking about.

    This may be an oprinion thing, but is it worth resetting the ECU after purchasing a used truck? My 07 I just got has 21k on it, and I obviously would have no idea how the previous owner drove it (aside from infrequently). Would resetting the ECU have any benefit to wiping out all the data/habits from his driving style, or do you think that over the next little while it will sort of work things out on its own?
    Resetting the ECU would clear everything right now....

    If you drove it for a while...yes in time....it would then learn your driving habits.

    Depends on how quickly you wanted it to learn. I personally just bought a 07 Prius (44mpg so far), I reset the ECU the day I bought it.

Page 1 of 2 12 LastLast

LinkBacks (?)

  1. 12-16-2013, 11:44 AM
  2. 05-10-2013, 04:16 PM
  3. 04-25-2013, 06:20 AM
  4. 02-18-2013, 07:58 AM
  5. 02-17-2013, 03:48 PM
  6. 02-06-2013, 04:13 PM
  7. 05-15-2012, 12:55 PM
  8. 09-30-2011, 12:11 PM
  9. 07-26-2011, 10:25 AM
  10. 05-04-2011, 10:19 PM
  11. 01-20-2011, 10:35 PM
  12. 01-08-2011, 06:51 PM
  13. 10-08-2010, 11:03 PM
  14. 07-10-2010, 05:29 PM
  15. 05-16-2010, 07:40 PM
  16. 12-14-2009, 11:39 AM
  17. 12-13-2009, 09:30 PM
  18. 02-27-2009, 10:55 AM
  19. 12-21-2008, 07:35 AM
  20. 12-11-2008, 01:48 PM
  21. 09-20-2008, 02:12 AM
  22. 06-09-2008, 08:11 PM
  23. 11-18-2007, 02:59 AM
  24. 11-15-2007, 04:07 PM

Similar Threads

  1. We Got Even MORE Jokes - Thread 4
    By Salty_Dog in forum Off-Topic
    Replies: 545
    Last Post: 07-07-2007, 07:45 AM
  2. Ways to fight back to school depression?
    By Brandon1 in forum Off-Topic
    Replies: 38
    Last Post: 08-28-2005, 02:08 PM
  3. Warranty Work
    By mmarlatt in forum Pricing and Dealers
    Replies: 1
    Last Post: 04-20-2005, 11:37 AM
  4. Replies: 5
    Last Post: 04-04-2005, 06:40 AM

Posting Permissions

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