ECU reset after alternator change?
Discussion
Hi Everyone
I'm back, hoping for some advice about a slightly more pressing (and worrying) issue....
Felt over the last week or so that the alternator in my wagon (04/WRX) might be playing up (occasional slow cranking, headlights dimming, etc.) so sent it into my regular mechanic for a quick alternator change. Upon checking in with him at the end of the day to see how it was going he informed me that after doing some research he'd discovered that the ECU might need a reset after the change, as it controls all sorts of charging and mapping parameters. Lo and behold, after changing it he called to tell me the car was playing up in all sorts of weird ways and not behaving itself at all. Before I take it to a main dealer and have my wallet assaulted, does anyone have any idea about this? I've found some info about doing a 'hard reset' of the ECU. Is that what I should be doing?
Again, any advice appreciated.
I'm back, hoping for some advice about a slightly more pressing (and worrying) issue....
Felt over the last week or so that the alternator in my wagon (04/WRX) might be playing up (occasional slow cranking, headlights dimming, etc.) so sent it into my regular mechanic for a quick alternator change. Upon checking in with him at the end of the day to see how it was going he informed me that after doing some research he'd discovered that the ECU might need a reset after the change, as it controls all sorts of charging and mapping parameters. Lo and behold, after changing it he called to tell me the car was playing up in all sorts of weird ways and not behaving itself at all. Before I take it to a main dealer and have my wallet assaulted, does anyone have any idea about this? I've found some info about doing a 'hard reset' of the ECU. Is that what I should be doing?
Again, any advice appreciated.
An ECU reset is when it loses its learned values. Those learned values are mainly to do with the scaling of the Mass Air Fuel sensor (MAF) and the resistance to knock of the fuel you have been putting into it.
That is pretty much it (look up 'learningview' for Subaru for a full picture).
To reset the ECU just disconnect the battery for a minute and put on the Hazard warning lights (this is just to release any last trickles of charge in the system)
OK, now your ECU is reset. How do you know? When you reconnect it will take a bit longer cranking over to start up.
To get all the learning values back in the system just drive around as normal. (all the b*ll*cks about Vishnu reset and holding your brake pedal whilst revving at 2800rpm is rubbish. You can monitor your learned values as you drive around and driving around normally is all you need to do)
However... I doubt it will fix all the weird stuff you are seeing but worth a go.
That is pretty much it (look up 'learningview' for Subaru for a full picture).
To reset the ECU just disconnect the battery for a minute and put on the Hazard warning lights (this is just to release any last trickles of charge in the system)
OK, now your ECU is reset. How do you know? When you reconnect it will take a bit longer cranking over to start up.
To get all the learning values back in the system just drive around as normal. (all the b*ll*cks about Vishnu reset and holding your brake pedal whilst revving at 2800rpm is rubbish. You can monitor your learned values as you drive around and driving around normally is all you need to do)
However... I doubt it will fix all the weird stuff you are seeing but worth a go.
cheesesliceking said:
I thought disconnecting the battery on a newage didnt reset the ECU?
Hi cheeselicker, disconnecting the battery has always reset the newage ecu. I've got a tactrix openport so can see the values clear on disconnect.Bob rawle also confirms on his project thread.
The confusion about the reset and what you do after to 'learn' the values came from some rubbish somebody wrote on scoobypedia and nasioc which has become fact.
Hi All
Sorry to dig up a 5yr old thread, I bought my current Scooby about 5yrs ago and the seller said always leave your air-con on, which was odd but fine. Within the first year I found my battery dead, thought nothing, replaced it with a brand new battery, which also completely died within 6 months.
What I discovered with a multimeter at that point was that unless I had either my headlights or air-con on then my alternator wasn't producing enough current to charge the battery properly (I forget the exact values as it was 4yrs ago), so assuming the alternator was duff, I went and had that replaced as well as another brand new battery, but again it is not charging enough unless headlights / air-con is running.
The garage said the ECU manages when to step up the demand and that is why, 4yrs on I drive with air-con on all the time, no battery issues.
1. Having read this thread, am I right in thinking all I needed to do was a simple ECU reset to recognise the newer alternator?
2. My only fear with disconnecting the battery is that the previous owner changed the alarm key code... and then lost the code, so I've previously only changed battery with engine running, so as not to lose the alarm's recognition of my key.
3. (afterthought) I have had my ECU remapped by Bob Rawle, which is ECUTEK I believe, would a hard reset of my ECU affect this also?
Therefore does anyone know if I remove the battery to clear the ECU (which I want to do for other reasons anyway, regardless of point 1), will I be locked out of my car with the key unrecognisable / or lose my remapping?
Cheers to any insight on these 3 points.
Sorry to dig up a 5yr old thread, I bought my current Scooby about 5yrs ago and the seller said always leave your air-con on, which was odd but fine. Within the first year I found my battery dead, thought nothing, replaced it with a brand new battery, which also completely died within 6 months.
What I discovered with a multimeter at that point was that unless I had either my headlights or air-con on then my alternator wasn't producing enough current to charge the battery properly (I forget the exact values as it was 4yrs ago), so assuming the alternator was duff, I went and had that replaced as well as another brand new battery, but again it is not charging enough unless headlights / air-con is running.
The garage said the ECU manages when to step up the demand and that is why, 4yrs on I drive with air-con on all the time, no battery issues.
1. Having read this thread, am I right in thinking all I needed to do was a simple ECU reset to recognise the newer alternator?
2. My only fear with disconnecting the battery is that the previous owner changed the alarm key code... and then lost the code, so I've previously only changed battery with engine running, so as not to lose the alarm's recognition of my key.
3. (afterthought) I have had my ECU remapped by Bob Rawle, which is ECUTEK I believe, would a hard reset of my ECU affect this also?
Therefore does anyone know if I remove the battery to clear the ECU (which I want to do for other reasons anyway, regardless of point 1), will I be locked out of my car with the key unrecognisable / or lose my remapping?
Cheers to any insight on these 3 points.
Edited by JJW_1978 on Thursday 7th March 13:34
Update - I found a link to ECUTEK that another poster had mentioned, they confirmed disconnecting the battery for an extended period will not erase any mapping. I also found other convincing details that a Sigma alarm does not forget its mapped keys once programmed either. This can only be done by re-mapping. It is non-volatile memory.
So I bit the bullet and did a hard reset of my ECU
The good news is nothing bad happened, key fobbed unlocked car once battery was reconnected, ECUTEK mapping is still perfectly fine.
The bad news is, I'm not convinced any reset happened. I've heard contradictions about new age imprezas cant be reset by disconnecting the battery like the classic ones can. During the re-learn process of running the car for 20 mins a couple of times, It did seem to improve the idle when the AC fans / lghts were off. But I soon found to get the proper voltage for charging I still need to have either AC or Headlights on . So it didn't fix that issue, and I don't know if it reset my LTFT which I was hoping for, but it still smell rich, so I don't think that was reset. My OBDII scanner only sees STFT which I fixed last week with a new O2 sensor.
Maybe I'll have to pay Subaru £45 to reset my ECU unless anyone knows a way of checking if disconnecting the battery actually works (for my 2006 STI)
So I bit the bullet and did a hard reset of my ECU
The good news is nothing bad happened, key fobbed unlocked car once battery was reconnected, ECUTEK mapping is still perfectly fine.
The bad news is, I'm not convinced any reset happened. I've heard contradictions about new age imprezas cant be reset by disconnecting the battery like the classic ones can. During the re-learn process of running the car for 20 mins a couple of times, It did seem to improve the idle when the AC fans / lghts were off. But I soon found to get the proper voltage for charging I still need to have either AC or Headlights on . So it didn't fix that issue, and I don't know if it reset my LTFT which I was hoping for, but it still smell rich, so I don't think that was reset. My OBDII scanner only sees STFT which I fixed last week with a new O2 sensor.
Maybe I'll have to pay Subaru £45 to reset my ECU unless anyone knows a way of checking if disconnecting the battery actually works (for my 2006 STI)
vxr2010 said:
test the alternator voltage , i don’t think on subaru’s that the charging system varies it’s voltage depending on charge , plus check all connections , there’s no reason to reset after fitting an alternator i did not need to when i did mine
Yes, what are the voltages with headlights/AC on and off?vxr2010 said:
should be around 14 . ? plus volts , mines 14.3 or so , if it’s less check belt is not slipping , if it’s not that it’s likely to be your alternator
I actually just checked mine - 2005 WRX. It's around 12.7 volts with headlights off, and 14.4 with headlights on.If the OP's car is the same then I'd use the multimeter to see what the drain is when everything is switched off.
Hi VXR2010 and NW942,
thanks for your interest in this revived thread, I'm not the OP, just currently experiencing the exact same symptoms.
As you asked, when idling with AC and headlights off 11.8V
when running with either AC or headlights, or both, 13.8V
there is a clear 5 sec delay between switching either on, and watching the rpm and voltage increase by a slight, but noticeable increase.
I am aware of several other people with completely different makes of car having this issue, I reckon there are probably thousands who don't even know it, and the death of the battery happens over 6 months, it only alarmed me as my battery was brand new with a 5yr warranty.
I know my battery is good and the alternator is good (both replaced more than once, with OEM).
It is a known issue, just not widely known. There's even you tube videos how to solder a resistor into the middle of 3 wires on your alternator (the step up/down one that goes to the ECU) to constantly fool it to step up at all times to 14V. I don't want to do this, but understand the principle.
I just hoped resetting the ECU would fix the issue and it didn't for me... but I am not convinced the reset was proper and might have to pay to do so.
It's had a new belt, 2 weeks ago, I think one of you asked, so its not that either.
Oh, and one of you asked about a drain when everything is off....
I read a really interesting forum post about the tracker on the 2001 to 2005 model being well know for killing batteries as they continue running 6hrs after engine off.
I don't have that, and my battery drain was a little high. I found that all 2006-07 hawkeye STI Spec-D like mine were all fitted with Traffic Master, a really Pony, pay as you go sat nav. I ripped that out so that my battery drain was negligible... so I am happy I have no power drain at engine off.
The issue is simply if I do not have headlights or AC on when driving then my battery does not charge.
I have yet to hear a permanent fix on this, and just wanted to add my exploration to this thread and retest the water if anyone else knew. Cheers
thanks for your interest in this revived thread, I'm not the OP, just currently experiencing the exact same symptoms.
As you asked, when idling with AC and headlights off 11.8V
when running with either AC or headlights, or both, 13.8V
there is a clear 5 sec delay between switching either on, and watching the rpm and voltage increase by a slight, but noticeable increase.
I am aware of several other people with completely different makes of car having this issue, I reckon there are probably thousands who don't even know it, and the death of the battery happens over 6 months, it only alarmed me as my battery was brand new with a 5yr warranty.
I know my battery is good and the alternator is good (both replaced more than once, with OEM).
It is a known issue, just not widely known. There's even you tube videos how to solder a resistor into the middle of 3 wires on your alternator (the step up/down one that goes to the ECU) to constantly fool it to step up at all times to 14V. I don't want to do this, but understand the principle.
I just hoped resetting the ECU would fix the issue and it didn't for me... but I am not convinced the reset was proper and might have to pay to do so.
It's had a new belt, 2 weeks ago, I think one of you asked, so its not that either.
Oh, and one of you asked about a drain when everything is off....
I read a really interesting forum post about the tracker on the 2001 to 2005 model being well know for killing batteries as they continue running 6hrs after engine off.
I don't have that, and my battery drain was a little high. I found that all 2006-07 hawkeye STI Spec-D like mine were all fitted with Traffic Master, a really Pony, pay as you go sat nav. I ripped that out so that my battery drain was negligible... so I am happy I have no power drain at engine off.
The issue is simply if I do not have headlights or AC on when driving then my battery does not charge.
I have yet to hear a permanent fix on this, and just wanted to add my exploration to this thread and retest the water if anyone else knew. Cheers
i think it’s still an alternator fault , it should show the same voltage all the time , i had a new alternator that was still faulty , the battery is only there to hold charge and start a car , the alternator on my monaro has intelligent charging so the voltage varies depending on battery charge and load , i don’t think subaru’s have that , i say that as the voltage in the fsti stays the same and if you load it it compensates , i would swap out the alternator and see how you go , in borehamwood herts .. i think it’s called unit exchange they will rebuild it for around 70£ and you can post it to them they will also test it , i would also check earth wires and add an extra earth wire
Update...
OK, so I can confirm Subaru New Age models do have "smart charge" and mine is working "properly"
They are designed to step up on demand, although in my opinion I'd rather it constantly charged my battery when driving,
and I don't like the idea of artificially increasing demand to ensure a constant charge (even though Subaru do not believe constant charge is required).
Furthermore, after not being able to find any local garage to reset my ECU, and attempting the online videos of disconnecting the battery for 30mins and re-learning a couple of times, I paid a Subaru dealer £82 !!! to do a full ECU diagnostic and then reset my ECU using their official Subaru diagnostic equipment.
They have confirmed "There is no way to hard reset an ECU in the new age models, they are constantly learning and do not need to relearn anything."
This official comment seems at odds with videos I have seen of new age imprezas being wiped of long term saved values and the ECU relearning.
They did show me print outs of various OBDII settings before, during a run and after, but couldn't read values like LTFT (long term fuel trim) with their official equipment. So I have no idea who's right/wrong. Just letting everyone know the official answer I got from one of their dealers.
OK, so I can confirm Subaru New Age models do have "smart charge" and mine is working "properly"
They are designed to step up on demand, although in my opinion I'd rather it constantly charged my battery when driving,
and I don't like the idea of artificially increasing demand to ensure a constant charge (even though Subaru do not believe constant charge is required).
Furthermore, after not being able to find any local garage to reset my ECU, and attempting the online videos of disconnecting the battery for 30mins and re-learning a couple of times, I paid a Subaru dealer £82 !!! to do a full ECU diagnostic and then reset my ECU using their official Subaru diagnostic equipment.
They have confirmed "There is no way to hard reset an ECU in the new age models, they are constantly learning and do not need to relearn anything."
This official comment seems at odds with videos I have seen of new age imprezas being wiped of long term saved values and the ECU relearning.
They did show me print outs of various OBDII settings before, during a run and after, but couldn't read values like LTFT (long term fuel trim) with their official equipment. So I have no idea who's right/wrong. Just letting everyone know the official answer I got from one of their dealers.
JJW_1978 said:
Update...
OK, so I can confirm Subaru New Age models do have "smart charge" and mine is working "properly"
They are designed to step up on demand, although in my opinion I'd rather it constantly charged my battery when driving,
and I don't like the idea of artificially increasing demand to ensure a constant charge (even though Subaru do not believe constant charge is required).
Furthermore, after not being able to find any local garage to reset my ECU, and attempting the online videos of disconnecting the battery for 30mins and re-learning a couple of times, I paid a Subaru dealer £82 !!! to do a full ECU diagnostic and then reset my ECU using their official Subaru diagnostic equipment.
They have confirmed "There is no way to hard reset an ECU in the new age models, they are constantly learning and do not need to relearn anything."
This official comment seems at odds with videos I have seen of new age imprezas being wiped of long term saved values and the ECU relearning.
They did show me print outs of various OBDII settings before, during a run and after, but couldn't read values like LTFT (long term fuel trim) with their official equipment. So I have no idea who's right/wrong. Just letting everyone know the official answer I got from one of their dealers.
"There is no way to hard reset an ECU in the new age models, they are constantly learning and do not need to relearn anything."OK, so I can confirm Subaru New Age models do have "smart charge" and mine is working "properly"
They are designed to step up on demand, although in my opinion I'd rather it constantly charged my battery when driving,
and I don't like the idea of artificially increasing demand to ensure a constant charge (even though Subaru do not believe constant charge is required).
Furthermore, after not being able to find any local garage to reset my ECU, and attempting the online videos of disconnecting the battery for 30mins and re-learning a couple of times, I paid a Subaru dealer £82 !!! to do a full ECU diagnostic and then reset my ECU using their official Subaru diagnostic equipment.
They have confirmed "There is no way to hard reset an ECU in the new age models, they are constantly learning and do not need to relearn anything."
This official comment seems at odds with videos I have seen of new age imprezas being wiped of long term saved values and the ECU relearning.
They did show me print outs of various OBDII settings before, during a run and after, but couldn't read values like LTFT (long term fuel trim) with their official equipment. So I have no idea who's right/wrong. Just letting everyone know the official answer I got from one of their dealers.
So what did they charge you £82 for, given that the dealer said they the ECU doesn't need to relearn anything?
You need a Tactrix cable https://www.tactrix.com/ and some free softaware such as Romraider (and a laptop!)
The cable costs about the same as the dealer charged you...
Whilst it is true that the ecu continues to "learn" and update it's reference tables, if you have had a long running fault (such as O2 sensor, vaccum leak etc) it will take a long time for the values - namely the Ignition Advance Multiplier (IAM) - to update to take advantage of the fault fix. If you reset the ECU, it loses all it's previously "learnt" values and can relearn afresh with the engine running correctly. This leads to improved performance.
on some newer shapes you can reset an ecu , the foresters i know you can , disconnect battery pump brake pedal about 50 times , you can leave it for 30 mins then put battery connections back on ,ecu reset , i had a boost solenoid issue and it had not settled its self down after being swapped this resolved it straight away and then ecu re learnt again , i also have done it with poor running issues , my better half kept using the throttle to start the car with as in depressed it , i did say don’t lol , this ecu reset was done again twice for good measure and it sorted itself out
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