ECU re-learn time
02-19-2003, 09:30 AM
#2
vicodin ... gift of life
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I heard you can reset your ECU like that by disconnecting your battery for maybe an hour or so then reconnect it, turn on your car, and let it idle for about 5 min. OR SO I HEARD... I don't know if this actually does it but I did it after I installed my catback, exhaust, and midpipe/cone...
I think the ECU also resets after so many thousand miles, I forget what the number was tho.
NOW, if you're talkin about resetting your CEL, read the stickies.
I think the ECU also resets after so many thousand miles, I forget what the number was tho.
NOW, if you're talkin about resetting your CEL, read the stickies.
02-19-2003, 10:04 AM
#4
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Originally posted by Street Reeper
I would think you would not need to reset it, and that it would learn any change immedialty. It is always reading and updating fuel and air mixtures so I would think that it is constantly learning.
I would think you would not need to reset it, and that it would learn any change immedialty. It is always reading and updating fuel and air mixtures so I would think that it is constantly learning.
02-19-2003, 10:37 AM
#5
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Originally posted by njmaxseltd
02-19-2003, 10:46 AM
#6
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Originally posted by Zirafa
I thought so too but let's assume you do reset your ECU by either disconnecting the battery or clearing the stored codes via the screw on the ECU itself. How long would it take then to realearn everything? Is it a few minutes or a few days or a few weeks?
I thought so too but let's assume you do reset your ECU by either disconnecting the battery or clearing the stored codes via the screw on the ECU itself. How long would it take then to realearn everything? Is it a few minutes or a few days or a few weeks?
So lets say you park your car for a year without driving it and the battery died, and in that time for some reason the O2 sensors went bad. When you started your car a year later with a new battery would it take your ECU a few minutes or a few weeks to LEARN that the o2 sensor is bad (because some would say the ECU was reset from having the car with no battery for so long) The obvious answer is it would find the code immediatly because it is constantly updating itself and running checks. Or think about this, you reset the ECU how long does it take for the ECU to provide the right air to fuel ratios, does your car stumble for a while after you change the battery or clear codes because the ECU is trying to learn the fuel curves? The answer again is no, it mixes them perfectly right from the start because it is constantly active in making any needed changes, that's why you have an ECU so it can think and make changes immediatly, rather than just having presettings.
02-19-2003, 10:54 AM
#7
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Originally posted by Street Reeper
Reseting the ECU with the screw only clears your CEL light. If you reset your computer and turned off the CEL, then hooked up an OBD-II it would still show that you had a faulty code even though your check engine light isn't on.
So lets say you park your car for a year without driving it and the battery died, and in that time for some reason the O2 sensors went bad. When you started your car a year later with a new battery would it take your ECU a few minutes or a few weeks to LEARN that the o2 sensor is bad (because some would say the ECU was reset from having the car with no battery for so long) The obvious answer is it would find the code immediatly because it is constantly updating itself and running checks. Or think about this, you reset the ECU how long does it take for the ECU to provide the right air to fuel ratios, does your car stumble for a while after you change the battery or clear codes because the ECU is trying to learn the fuel curves? The answer again is no, it mixes them perfectly right from the start because it is constantly active in making any needed changes, that's why you have an ECU so it can think and make changes immediatly, rather than just having presettings.
Reseting the ECU with the screw only clears your CEL light. If you reset your computer and turned off the CEL, then hooked up an OBD-II it would still show that you had a faulty code even though your check engine light isn't on.
So lets say you park your car for a year without driving it and the battery died, and in that time for some reason the O2 sensors went bad. When you started your car a year later with a new battery would it take your ECU a few minutes or a few weeks to LEARN that the o2 sensor is bad (because some would say the ECU was reset from having the car with no battery for so long) The obvious answer is it would find the code immediatly because it is constantly updating itself and running checks. Or think about this, you reset the ECU how long does it take for the ECU to provide the right air to fuel ratios, does your car stumble for a while after you change the battery or clear codes because the ECU is trying to learn the fuel curves? The answer again is no, it mixes them perfectly right from the start because it is constantly active in making any needed changes, that's why you have an ECU so it can think and make changes immediatly, rather than just having presettings.
02-19-2003, 11:05 AM
#8
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Originally posted by Street Reeper
Reseting the ECU with the screw only clears your CEL light. If you reset your computer and turned off the CEL, then hooked up an OBD-II it would still show that you had a faulty code even though your check engine light isn't on.
Reseting the ECU with the screw only clears your CEL light. If you reset your computer and turned off the CEL, then hooked up an OBD-II it would still show that you had a faulty code even though your check engine light isn't on.
02-19-2003, 11:09 AM
#9
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Originally posted by Miasma
i dont think that is accurate. if you reset the ECU, the light will go out until it detects a consistently reoccuring problem. if it is a foreward O2 sensor, it will detect it immediatly and when you hook it up to an OBD-II scanner, it would show up. BUT, if you have an O2 sensor issue, replace it, and reset the ECU, the CEL and the code is gone. So, resetting the ECU does more than clear the CEL, but I do agree that it is not actually resetting the whole ECU such that it has to relearn your boost, exhaust mods etc...
i dont think that is accurate. if you reset the ECU, the light will go out until it detects a consistently reoccuring problem. if it is a foreward O2 sensor, it will detect it immediatly and when you hook it up to an OBD-II scanner, it would show up. BUT, if you have an O2 sensor issue, replace it, and reset the ECU, the CEL and the code is gone. So, resetting the ECU does more than clear the CEL, but I do agree that it is not actually resetting the whole ECU such that it has to relearn your boost, exhaust mods etc...
02-19-2003, 11:27 AM
#11
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Originally posted by Street Reeper
it sees the good o2 sensor and immediatly updates.
it sees the good o2 sensor and immediatly updates.
the software in these is incredibly advanced, they are extremely tolerant of failed components and still allow the car to run. I am not sure if the nissan ECU's are single, double, triple, or greater, fault tolerant, but i mean, even if a MAF and an O2 sensor die, i think the car can still be driven to a repair shop, that is infreakincredible. Compare that to a carbureated car where there are no sensors per say, just this idea that air supply is constant, if anything major changes, like air quality, quantity, the carbureator's function is severely diminished. Injected cars can adapt to SOOOO many scenerios, and adapt well, simply amazing IMO.
02-19-2003, 04:12 PM
#12
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Well, what is curious to know is if disconnecting your battery ACTUALLY DOES reset it... someone w/ a CEL on already could test this and let us know. Just disconnect ure battery for an hour or something, hook it back up and when u start the car see if the CEL comes on immediately.
02-19-2003, 04:20 PM
#13
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Originally posted by nadir_s
Well, what is curious to know is if disconnecting your battery ACTUALLY DOES reset it... someone w/ a CEL on already could test this and let us know. Just disconnect ure battery for an hour or something, hook it back up and when u start the car see if the CEL comes on immediately.
Well, what is curious to know is if disconnecting your battery ACTUALLY DOES reset it... someone w/ a CEL on already could test this and let us know. Just disconnect ure battery for an hour or something, hook it back up and when u start the car see if the CEL comes on immediately.
02-19-2003, 04:24 PM
#14
vicodin ... gift of life
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Originally posted by Miasma
doesnt the reset procedure take like 24+ hours? the capacitors will retain a charge for a long time.
doesnt the reset procedure take like 24+ hours? the capacitors will retain a charge for a long time.
hmm... well I don't know if it's as long as 24 hours, but I heard leaving it disconnected overnight was plenty time (what i do usually). I mean if you think about it, our radio loses channel memory within like 1-2 hours or something... so the capicitors must be drained by that time.
02-19-2003, 04:52 PM
#15
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Originally posted by nadir_s
hmm... well I don't know if it's as long as 24 hours, but I heard leaving it disconnected overnight was plenty time (what i do usually). I mean if you think about it, our radio loses channel memory within like 1-2 hours or something... so the capicitors must be drained by that time.
hmm... well I don't know if it's as long as 24 hours, but I heard leaving it disconnected overnight was plenty time (what i do usually). I mean if you think about it, our radio loses channel memory within like 1-2 hours or something... so the capicitors must be drained by that time.
02-19-2003, 05:06 PM
#16
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Originally posted by Miasma
the radio and clock will loose settings instantly.
the radio and clock will loose settings instantly.
02-19-2003, 05:10 PM
#17
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Originally posted by nadir_s
how come? If there are capicitors connected to the circuit, it shoudln't. Unless... there are capicitors that are on a closed circuit w/ the ECU. haha dunno, someone needs to try it.
how come? If there are capicitors connected to the circuit, it shoudln't. Unless... there are capicitors that are on a closed circuit w/ the ECU. haha dunno, someone needs to try it.
the memory in the ECU is different, fundamentally made of capacitors, but not hooked up.
you dont have any sort of 'back up battery' once you unhook the (-) terminal on the batt, no power goes to anything to retain capacitor charge - unless the device was designed to retain memory - ecu.
02-19-2003, 05:14 PM
#18
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Originally posted by Miasma
capacitors discharge VERY fast when hooked up to a resistance, therefore your settings clear for the radio instantly.
the memory in the ECU is different, fundamentally made of capacitors, but not hooked up.
you dont have any sort of 'back up battery' once you unhook the (-) terminal on the batt, no power goes to anything to retain capacitor charge - unless the device was designed to retain memory - ecu.
capacitors discharge VERY fast when hooked up to a resistance, therefore your settings clear for the radio instantly.
the memory in the ECU is different, fundamentally made of capacitors, but not hooked up.
you dont have any sort of 'back up battery' once you unhook the (-) terminal on the batt, no power goes to anything to retain capacitor charge - unless the device was designed to retain memory - ecu.
02-19-2003, 06:10 PM
#19
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Originally posted by Street Reeper
I would think you would not need to reset it, and that it would learn any change immedialty. It is always reading and updating fuel and air mixtures so I would think that it is constantly learning.
I would think you would not need to reset it, and that it would learn any change immedialty. It is always reading and updating fuel and air mixtures so I would think that it is constantly learning.
Why have the ECU learn EVERYTHING, not just the new mod.
PLUS (pet peeve) you loose you radio presets.
02-19-2003, 09:45 PM
#20
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I agree with most of the above. 
However, when adding a mod, your ECU doesn't just remap everything and adjust completely to it within seconds. I say it takes a good tank of gas to relearn the the most efficient way to deliver the power. Why?
#1 After adding a y-pipe it took my intake about 1 week to come back to life. After the install it (the intake) was very quiet, like it wasn't getting enough air in. Track results that weekend (1day later) were less than expected. Two weeks later, the intake "sound" was back to normal, and the track times improved greatly!
#2 After adding the OBX cat-back, the exhaust was very loud, and very noticeable. Couldn't even hear the intake over it. After about 2 weeks of driving the exhaust became more quiet, and the intake turned back into the more dominate sound, (depending on rpm of course). You could say that I was just getting used to the exhaust, however I am not the only one to notice these changes.
But, like mentioned above, I don't see much reason to reset the ECU, it should relearn just as fast on its on.
However, when adding a mod, your ECU doesn't just remap everything and adjust completely to it within seconds. I say it takes a good tank of gas to relearn the the most efficient way to deliver the power. Why?
#1 After adding a y-pipe it took my intake about 1 week to come back to life. After the install it (the intake) was very quiet, like it wasn't getting enough air in. Track results that weekend (1day later) were less than expected. Two weeks later, the intake "sound" was back to normal, and the track times improved greatly!
#2 After adding the OBX cat-back, the exhaust was very loud, and very noticeable. Couldn't even hear the intake over it. After about 2 weeks of driving the exhaust became more quiet, and the intake turned back into the more dominate sound, (depending on rpm of course). You could say that I was just getting used to the exhaust, however I am not the only one to notice these changes.
But, like mentioned above, I don't see much reason to reset the ECU, it should relearn just as fast on its on.
02-19-2003, 11:12 PM
#21
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Originally posted by Victim64
I agree with most of the above.
However, when adding a mod, your ECU doesn't just remap everything and adjust completely to it within seconds. I say it takes a good tank of gas to relearn the the most efficient way to deliver the power. Why?
#1 After adding a y-pipe it took my intake about 1 week to come back to life. After the install it (the intake) was very quiet, like it wasn't getting enough air in. Track results that weekend (1day later) were less than expected. Two weeks later, the intake "sound" was back to normal, and the track times improved greatly!
#2 After adding the OBX cat-back, the exhaust was very loud, and very noticeable. Couldn't even hear the intake over it. After about 2 weeks of driving the exhaust became more quiet, and the intake turned back into the more dominate sound, (depending on rpm of course). You could say that I was just getting used to the exhaust, however I am not the only one to notice these changes.
But, like mentioned above, I don't see much reason to reset the ECU, it should relearn just as fast on its on.
I agree with most of the above.
However, when adding a mod, your ECU doesn't just remap everything and adjust completely to it within seconds. I say it takes a good tank of gas to relearn the the most efficient way to deliver the power. Why?
#1 After adding a y-pipe it took my intake about 1 week to come back to life. After the install it (the intake) was very quiet, like it wasn't getting enough air in. Track results that weekend (1day later) were less than expected. Two weeks later, the intake "sound" was back to normal, and the track times improved greatly!
#2 After adding the OBX cat-back, the exhaust was very loud, and very noticeable. Couldn't even hear the intake over it. After about 2 weeks of driving the exhaust became more quiet, and the intake turned back into the more dominate sound, (depending on rpm of course). You could say that I was just getting used to the exhaust, however I am not the only one to notice these changes.
But, like mentioned above, I don't see much reason to reset the ECU, it should relearn just as fast on its on.
02-20-2003, 02:04 AM
#22
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Originally posted by Zirafa
OK, here it is:
How long does it usually take for the ECU to relearn everything after resetting?
I searched but couldn't find a specific answer. Anyone know?
OK, here it is:
How long does it usually take for the ECU to relearn everything after resetting?
I searched but couldn't find a specific answer. Anyone know?
The re-learn procedure is mainly used by mechanics after working on the car to speed up the ECU relearning process, to minimize possible drivabilty problems ( and complaints) when the customer drives away. If you drive your car for several days after disconnecting the battery, the computer will eventually relearn what it needs to know to operate the engine properly.
FYI: My old Ford SHO was running odd and dying randomly at idle. The problem turned out to be a slightly loose battery ground cable. It would cause the computer to keep re-setting and re-learning. Once I fixed the cable, the engine problems went away. I bet a shop would have ripped me for that fix, if they ever found the problem. So if your car has a comouyter, make sure your battery and ground cables are good. Even a bad battery that puts out a low (9.5 volts or less) will cause weird engine operation problems because when car is started, the starter drops the voltage drops so low that the computer will re-set.
09-06-2003, 09:29 PM
#23
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Originally Posted by Bgohan
The procedure varies between auto and manual trannys. It can take 40 or more key starts to memorize certain patterns. Until then, it uses a default program. The car may idle or run rough, stumble, hesitate, run lean or rich, shift poorly, and get poor mileage until computer gets settled down.
Any idea on how long it should take? (In miles)
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