Resetting ECU???
05-01-03, 10:25 PM
#1
Full Member
Thread Starter
Join Date: Sep 2002
Location: Calgary
Posts: 118
Likes: 0
Received 0 Likes
on
0 Posts
Resetting ECU???
FOund this at the following site, can we do this to the FD???
http://www.geocities.com/proton_aero...k_unichip.html
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 value 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 clear.
How-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. In a DSM, this is the fuse that controls the footlights that go on when you open your car door. On a 1990-1994 DSM, this is the 10A fuse in the lower-right-hand-corner of the fuse box near the driver's footwell. On a 1995+ DSM, this is the 10A fuse on the right-hand side of the middle row of the same fuse box. Pull this fuse with the key out and wait for about 15 seconds, then put the fuse back in. 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. Sometimes people like to pull this fuse when they are working on or cleaning the
interior of their car. This fuse also controls the lights that go on when you open the door, so many pull this fuse so they don't drain the battery during their job.
However, this will also cut backup power to the ECU. 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.
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.
On a DSM, 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? On a DSM, no. 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.
Other Resources:
Resetting the ECU
Take the negative terminal off the battery for about 15 minutes. (on 97+ cars) for 96 and below it's only like 2-3 minutes. this will reset the ecu. (Matthew Evans, Nov 20, 1998) Pull the the negative cable off for a few minutes or the ECU 10a fuse. Once connected, you'd experience dipping idle for a few days. This is normal as the ECU learns the real world conditions. Check out tmo.com for more info. (Gino, Jan 7, 99)
Clearing diagnostic trouble codes
I) After I fixed the problem, I disconnected the battery, then reconnected it.
According to the manual, that will erase the diagnostic trouble codes. If you've fixed the problem, the MIL should not come on again. That worked for me. (Mike,
Nov 18, 98)
ECU (Engine Control Unit) - This is the brain of the car. It uses the input from all of the sensors on the engine to determine optimum spark advance and fuel delivery for the engine. Most modern ECUs can also control other items such as the air conditioner, alternator, and choke. The reason all modern cars have ECUs instead of mechanical carbuerators is that ECUs can better respond to the many variables that make up an engine's performance curve. Remember the days of tuning jets on a carb, and playing with chokes? An ECU can do equivalent control of those things all by itself and compensate for (tune) the engine as it ages. Computers were initially introduced into automobiles to bring their smog levels down. Now they are used to eke out the last bit of performance out of relatively tiny four-cylinder engines. EPROM - Let's start with the last three letters. ROM means Read-Only Memory. This is a permanent storage place for computer programs. Computers can read their operating program from this device. It cannot be written over (as opposed to RAM, which we are sure you have heard of). It is made with the computer program already etched in right at the factory. PROM means Programmable ROM. A PROM is a device like a ROM, except that it leaves the factory blank and can be filled with a program once, and only once. An EPROM is an Erasable PROM. It can be erased after being written, but only with an intense ultra-violet light source. That is typically why you see thick labels on them - so they won't accidentally get erased due to prolonged exposure to sunlight or
flourescent lights. Why don't auto manufacturers use ROMs or PROMs instead of EPROMS? We suspect that at the beginning of a model year, many things in the
ECU computer program are still in flux. After all, the smog testing for the entire model line may not have been completed yet, and the smog rules themselves might
have changed since they designed the car. In order to accomodate any last minute quick fixes, the manufacturers use EPROMs so they won't get stuck with a bunch of ECUs that have the wrong program in them. MAF (Mass Airflow Sensor) or MAS (Mass Air Sensor) - Most commonly found on Mitsubishi vehicles, this sensor is used by the ECU to determine the amount of air entering the engine. Notice that "amount of air" is different from "volume of air" depending on the air temperature and pressure. The MAF actually uses three different sensors to determine the amount of air. The most important sensor is the airflow sensor. For this task, Mitsubishi employs a Karmaan Vortex sensor. Long story short, this sensor works by disturbing a laminar flow of air, causing vortices which spin in alternate directions. An ultrasonic transducer detects these vortices, and sends a pulse to the ECU every time one passes by. The MAF also has a barometric pressure sensor and temperature sensor. If you remember PV=nRT from freshman chemistry, you'll see
that we have P, V, and T - since R is a constant, we now have n, which is the amount of air. Although a bit more restrictive than other methods due to the need
for a laminar flow, the Mitsubishi MAF has the advantage of not depending on the volumetric efficiency of the engine. Thus, when you upgrade various engine, intake, or exhaust components, you do not neccessarily have to reconfigure the ECU's fuel and spark program.
http://www.geocities.com/proton_aero...k_unichip.html
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 value 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 clear.
How-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. In a DSM, this is the fuse that controls the footlights that go on when you open your car door. On a 1990-1994 DSM, this is the 10A fuse in the lower-right-hand-corner of the fuse box near the driver's footwell. On a 1995+ DSM, this is the 10A fuse on the right-hand side of the middle row of the same fuse box. Pull this fuse with the key out and wait for about 15 seconds, then put the fuse back in. 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. Sometimes people like to pull this fuse when they are working on or cleaning the
interior of their car. This fuse also controls the lights that go on when you open the door, so many pull this fuse so they don't drain the battery during their job.
However, this will also cut backup power to the ECU. 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.
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.
On a DSM, 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? On a DSM, no. 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.
Other Resources:
Resetting the ECU
Take the negative terminal off the battery for about 15 minutes. (on 97+ cars) for 96 and below it's only like 2-3 minutes. this will reset the ecu. (Matthew Evans, Nov 20, 1998) Pull the the negative cable off for a few minutes or the ECU 10a fuse. Once connected, you'd experience dipping idle for a few days. This is normal as the ECU learns the real world conditions. Check out tmo.com for more info. (Gino, Jan 7, 99)
Clearing diagnostic trouble codes
I) After I fixed the problem, I disconnected the battery, then reconnected it.
According to the manual, that will erase the diagnostic trouble codes. If you've fixed the problem, the MIL should not come on again. That worked for me. (Mike,
Nov 18, 98)
ECU (Engine Control Unit) - This is the brain of the car. It uses the input from all of the sensors on the engine to determine optimum spark advance and fuel delivery for the engine. Most modern ECUs can also control other items such as the air conditioner, alternator, and choke. The reason all modern cars have ECUs instead of mechanical carbuerators is that ECUs can better respond to the many variables that make up an engine's performance curve. Remember the days of tuning jets on a carb, and playing with chokes? An ECU can do equivalent control of those things all by itself and compensate for (tune) the engine as it ages. Computers were initially introduced into automobiles to bring their smog levels down. Now they are used to eke out the last bit of performance out of relatively tiny four-cylinder engines. EPROM - Let's start with the last three letters. ROM means Read-Only Memory. This is a permanent storage place for computer programs. Computers can read their operating program from this device. It cannot be written over (as opposed to RAM, which we are sure you have heard of). It is made with the computer program already etched in right at the factory. PROM means Programmable ROM. A PROM is a device like a ROM, except that it leaves the factory blank and can be filled with a program once, and only once. An EPROM is an Erasable PROM. It can be erased after being written, but only with an intense ultra-violet light source. That is typically why you see thick labels on them - so they won't accidentally get erased due to prolonged exposure to sunlight or
flourescent lights. Why don't auto manufacturers use ROMs or PROMs instead of EPROMS? We suspect that at the beginning of a model year, many things in the
ECU computer program are still in flux. After all, the smog testing for the entire model line may not have been completed yet, and the smog rules themselves might
have changed since they designed the car. In order to accomodate any last minute quick fixes, the manufacturers use EPROMs so they won't get stuck with a bunch of ECUs that have the wrong program in them. MAF (Mass Airflow Sensor) or MAS (Mass Air Sensor) - Most commonly found on Mitsubishi vehicles, this sensor is used by the ECU to determine the amount of air entering the engine. Notice that "amount of air" is different from "volume of air" depending on the air temperature and pressure. The MAF actually uses three different sensors to determine the amount of air. The most important sensor is the airflow sensor. For this task, Mitsubishi employs a Karmaan Vortex sensor. Long story short, this sensor works by disturbing a laminar flow of air, causing vortices which spin in alternate directions. An ultrasonic transducer detects these vortices, and sends a pulse to the ECU every time one passes by. The MAF also has a barometric pressure sensor and temperature sensor. If you remember PV=nRT from freshman chemistry, you'll see
that we have P, V, and T - since R is a constant, we now have n, which is the amount of air. Although a bit more restrictive than other methods due to the need
for a laminar flow, the Mitsubishi MAF has the advantage of not depending on the volumetric efficiency of the engine. Thus, when you upgrade various engine, intake, or exhaust components, you do not neccessarily have to reconfigure the ECU's fuel and spark program.
05-01-03, 10:47 PM
#2
Glug Glug Glug Burp
Join Date: Jan 2002
Location: Scott AFB, IL
Posts: 3,819
Likes: 0
Received 0 Likes
on
0 Posts
Wow. That's a lot of reading! Anyway, remove the negative terminal. Get in car and step and hold brake for 30 seconds. I don't know if the brake thing really helps... But that's how I reset mine!
JUstin
JUstin
05-02-03, 06:54 AM
#3
HARRRRRRRRR
Join Date: Jan 2002
Location: Marietta GA
Posts: 1,858
Likes: 0
Received 0 Likes
on
0 Posts
Originally posted by jdhuegel1
Wow. That's a lot of reading! Anyway, remove the negative terminal. Get in car and step and hold brake for 30 seconds. I don't know if the brake thing really helps... But that's how I reset mine!
JUstin
Wow. That's a lot of reading! Anyway, remove the negative terminal. Get in car and step and hold brake for 30 seconds. I don't know if the brake thing really helps... But that's how I reset mine!
JUstin
Trending Topics
05-02-03, 10:21 PM
#8
Glug Glug Glug Burp
Join Date: Jan 2002
Location: Scott AFB, IL
Posts: 3,819
Likes: 0
Received 0 Likes
on
0 Posts
Originally posted by 93BlackFD
the brake thing makes your brakelight drain the ECu's capacitors (stored power)
the brake thing makes your brakelight drain the ECu's capacitors (stored power)
01-24-07, 05:52 PM
#11
Originally Posted by Mahjik
It could until the ECU re-learns...
Stupid question but will that problem happen after CONTINUOUS relearning?
Cause right now my idle is funked up again. Well not really at idle but with the clutch in, the rpms jump a bit and when im driving and i clutch in. The rpms drop down fast to about 1000rpm, then back up to about 1300rpm which is where my idle normally is (for my car anyhow).
Reason why im asking is because i been disconnecting the battery cable in the winter after EVERY drive. Cause usually i drive it like once or twice a week, then it sits. I dont want the battery to die because of the cold weather so i disconnect the cable. But i been doing this since i owned the car.
Maybe all those times really made an impact?
ONLY recent thing i did was install a radio, do you think that could be it? Im sure i grounded the radio correctly, this is my 3rd radio i put into this car.
I just to be sure cause then im gonna drive the car around like this til it relearns or something.
I dont understand, 3 days ago before the radio install the car was absolutely normal. I have a feeling its because of the radio.
01-24-07, 07:17 PM
#12
Rotary Enthusiast
Join Date: Mar 2003
Location: STL Area
Posts: 931
Likes: 0
Received 0 Likes
on
0 Posts
What an old thread....
But, I don't think it's your ECU. Try checking the ISC, TPS, and make sure the wax rod is moving in and out. My wax rod was stuck for the longest time, keeping one of the throttle plates open.
Did you accendentally reset the ECU? Just as everyone has said, you have to hold the brake down for 15 secs with the battery disconnected. I don't remember how long it takes the ECU to relearn its idle settings.
But, I don't think it's your ECU. Try checking the ISC, TPS, and make sure the wax rod is moving in and out. My wax rod was stuck for the longest time, keeping one of the throttle plates open.
Did you accendentally reset the ECU? Just as everyone has said, you have to hold the brake down for 15 secs with the battery disconnected. I don't remember how long it takes the ECU to relearn its idle settings.
01-24-07, 07:22 PM
#13
Originally Posted by DrunkenBowler
What an old thread....
But, I don't think it's your ECU. Try checking the ISC, TPS, and make sure the wax rod is moving in and out. My wax rod was stuck for the longest time, keeping one of the throttle plates open.
Did you accendentally reset the ECU? Just as everyone has said, you have to hold the brake down for 15 secs with the battery disconnected. I don't remember how long it takes the ECU to relearn its idle settings.
But, I don't think it's your ECU. Try checking the ISC, TPS, and make sure the wax rod is moving in and out. My wax rod was stuck for the longest time, keeping one of the throttle plates open.
Did you accendentally reset the ECU? Just as everyone has said, you have to hold the brake down for 15 secs with the battery disconnected. I don't remember how long it takes the ECU to relearn its idle settings.
ISC is brand new and TPS was adjusted 3 months ago to proper spec.
I did the TB mod so the wax rod screw? or whatever its called, the one with the tiny spring on it is turned in all the way.
But idk, the car was absolutely fine on my last drive which was this past sunday. And when i installed the radio yesterday, today is when it acted funny.
I touched nothing else in the engine bay.
Thats why i have a feeling its the radio? I know its a long shot but idk, our cars electrical system is weird as hell.
And i know about the resetting the ECU however in the long first post in this thread, they stated if you unplug the negative for 15 minutes ,it resets the ecu. Maybe that still applies to our cars? Cause if so, i been resetting my ecu like a million times already. lol
Should i try to reset the ECU the real way?
01-25-07, 10:53 AM
#14
Originally Posted by 1QWIK7
Should i try to reset the ECU the real way?
Here's a test:
Originally Posted by FDjunkie
I tested the E/L unit by grounding the TEN connection at the diagnostic connector, and attached a small lamp to the FEN (I think this is right, but don't have my FWM with me right now) and B+ connector. With the ignition key on you can test each E/L input one at a time, plus neutral, clutch, etc. The lamp lights (ECU only supplies 20~30 ma so this has to be a very small lamp, or use your VOM in series) when the ECU responds to each input switch, thereby testing the entire circuit. Check out section F of FWM on Electric Load (E/L) Control System, around F-135 or so I think.
01-25-07, 11:12 AM
#15
Senior Member
iTrader: (1)
Join Date: Feb 2004
Location: ohio
Posts: 688
Likes: 0
Received 0 Likes
on
0 Posts
ecu's learn .....obd2 ecu in 95 and up cars learn even more ...its a pain in the ***..they detune the car to get better gas mileage...
found this out researching my prelude ....thats why honda guys switch over to a obd 1 ecu and control it with hondata...still new to the fd ecu
i assume were obd 1 ???
also not sure about our cars, but in some models, you disconnect the battery then reconnect it, take the car over 55-60mph that resets it also...
brad
found this out researching my prelude ....thats why honda guys switch over to a obd 1 ecu and control it with hondata...still new to the fd ecu
i assume were obd 1 ???
also not sure about our cars, but in some models, you disconnect the battery then reconnect it, take the car over 55-60mph that resets it also...
brad
01-25-07, 02:51 PM
#17
Originally Posted by vtakk eg
will restting help you unflood ? like stated aboue?
01-25-07, 03:16 PM
#18
Originally Posted by Mahjik
It couldn't hurt, but it sounds like you may have another issue. There is also the Electric Load module that you might test.
Here's a test:
Here's a test:
Damn.
So def the radio couldnt be an issue to this correct?
Its too cold to go check right away to eliminate this possible factor but i find it soo wierd that this past sunday my car was absolutely fine. 2 days ago i installed a radio, then yesterday car acted funny..
PS. OOO wait wait. Last thursday i finished the TB coolant mod because i had bought a TB couple of months ago but i forgot to modify this TB so i had a high idle. But i didnt drive the car that day, i just started it to make sure my idle would be normal and it did go normal. Only sunday i drove it and it was still normal.
Do you think the ECU is trying to re-learn this TB mod fix i did and maybe got all screwy??
Idk
Thread
Thread Starter
Forum
Replies
Last Post
Erosangel
3rd Generation Specific (1993-2002)
5
09-18-15 04:06 PM
