How does the ECU/PCM remapping/reset work?
Discussion
I know absolutely nothing about ECU tuning so apologies if some of these questions appear dumb.
Q1) I've read information where people write "ECU/PCM". Is the ECU & PCM one of the same thing or are they two completely seperate systems?
ECU - Electronic Control Module
PCM - Powertrain Control Module
Q2) When mapping, do you map the ECU, the PCM, or both?
AFAIK the ECU/PCM's in the cars have the ability to 'adapt' to new components and the way that they are driven. A good example of this is uk_hsv's magnificent thread on modifying the air box to have a second 76/84mm hole. Although results would have been seen in a couple of days, immediate results were achieved by doing a PCM reset. How are those results possible (See Q3)?
Q3) How & why does the PCM/ECU reset actually work? Are there 2 areas to the ECU chip (upper & lower) where by the upper (for example) holds the original unmodified map and the lower holds the adapted/modified map? When doing the reset where does the original data come from, if indeed it exists in the first place? The reason I ask is that people on the LS1 forums have achieved results from "I see no difference" through to "Oh my God, it's like my car's been remapped". How is this possible if there isn't an original map to fall back to?
We all know that the remapping of the ECU aims to get the best possible performance from the engine by modifying the original GM Maps. (To those that haven't had it done.....you're missing out)
Q4) Has anyone who's had their ECU remapped ever noticed a deterioration in performance over a long period of 'normal' day-to-day driving followed by a day of vigerous driving (e.g. track day)? In other words, does the ECU's ability to adapt during day-to-day driving affect the performance on the vigerous driving day?
Q5) Hypothetical Q: I've just had my ECU remapped. If I did nothing with the car other than pootle around to & from work or along the motorways for 6months and then take it back to the original remapper would I expect to see a performance degredation between the original and then current dyno results? If so would a PCM reset get me the original performance back? If 'yes', then in your opinion what would be your recommended time period between PCM resets?
Q6) If one has the engine remapped & then performs a PCM reset on the system would I go back to the original GM Maps or would I default back to the map installed by the tuner?
Q7) What's the Manufacturer/Model of the ECU chip? This might help answer some of my Q's
Q8) If anyone has any websites or documents that would aid my learning I'd be most appreciative. I'm not about to get into tuning or steal anybody's work. I'm just highly curious on this subject matter. If anyone would be willing to provide a bogus/traning .DAT file for free, you'd be my hero.
As always your replies are greatfully received & I apologise for the large initial post. It really warrants somebody who knows this stuff drawing it out on a piece of paper.
Q1) I've read information where people write "ECU/PCM". Is the ECU & PCM one of the same thing or are they two completely seperate systems?
ECU - Electronic Control Module
PCM - Powertrain Control Module
Q2) When mapping, do you map the ECU, the PCM, or both?
AFAIK the ECU/PCM's in the cars have the ability to 'adapt' to new components and the way that they are driven. A good example of this is uk_hsv's magnificent thread on modifying the air box to have a second 76/84mm hole. Although results would have been seen in a couple of days, immediate results were achieved by doing a PCM reset. How are those results possible (See Q3)?
Q3) How & why does the PCM/ECU reset actually work? Are there 2 areas to the ECU chip (upper & lower) where by the upper (for example) holds the original unmodified map and the lower holds the adapted/modified map? When doing the reset where does the original data come from, if indeed it exists in the first place? The reason I ask is that people on the LS1 forums have achieved results from "I see no difference" through to "Oh my God, it's like my car's been remapped". How is this possible if there isn't an original map to fall back to?
We all know that the remapping of the ECU aims to get the best possible performance from the engine by modifying the original GM Maps. (To those that haven't had it done.....you're missing out)
Q4) Has anyone who's had their ECU remapped ever noticed a deterioration in performance over a long period of 'normal' day-to-day driving followed by a day of vigerous driving (e.g. track day)? In other words, does the ECU's ability to adapt during day-to-day driving affect the performance on the vigerous driving day?
Q5) Hypothetical Q: I've just had my ECU remapped. If I did nothing with the car other than pootle around to & from work or along the motorways for 6months and then take it back to the original remapper would I expect to see a performance degredation between the original and then current dyno results? If so would a PCM reset get me the original performance back? If 'yes', then in your opinion what would be your recommended time period between PCM resets?
Q6) If one has the engine remapped & then performs a PCM reset on the system would I go back to the original GM Maps or would I default back to the map installed by the tuner?
Q7) What's the Manufacturer/Model of the ECU chip? This might help answer some of my Q's
Q8) If anyone has any websites or documents that would aid my learning I'd be most appreciative. I'm not about to get into tuning or steal anybody's work. I'm just highly curious on this subject matter. If anyone would be willing to provide a bogus/traning .DAT file for free, you'd be my hero.
As always your replies are greatfully received & I apologise for the large initial post. It really warrants somebody who knows this stuff drawing it out on a piece of paper.
I will try and help here.............one question at a time.
Cars used to have a ECU (Engine control Module) but modern cars now have a PCM (Powertrain control Module) It is so called because it runs the engine, gearbox (mostly auto) ABS and Traction control.
Our Holden's/Vauxhall's also have a BCM (Body control Module)which is in charge of instruments, lights etc etc.
The new 6.0Ltr LS2 cars use a CAN/BUS system which links all the cars electric's together.
This new system will allow the intergration of some very cool stuff like launch control....But it is not for the fait harted tuner.............
Cars used to have a ECU (Engine control Module) but modern cars now have a PCM (Powertrain control Module) It is so called because it runs the engine, gearbox (mostly auto) ABS and Traction control.
Our Holden's/Vauxhall's also have a BCM (Body control Module)which is in charge of instruments, lights etc etc.
The new 6.0Ltr LS2 cars use a CAN/BUS system which links all the cars electric's together.
This new system will allow the intergration of some very cool stuff like launch control....But it is not for the fait harted tuner.............
When you preform a PCM reset you wipe out any learnt/adapted info and the car reverts to the base tune, before the car has made any alterations it needed to to maitain the cars systems.
The PCM reset will have varing results............
If the car has been running at its optimum a reset will have no effect but a car running poorly (because of tuning, poor fuel etc) the reset will have more effect...........
When you change anything on the engine it will have an effect on the tune, but the car can adjust to cope within a certain range.
But the car can only adjust so far before it shows an error code.
A case in point is fitting headers, cat bypass and catback system will push the cars fuel trims to around 20%-25% and this causes the car to show a code (as a few club members have seen!!!!)
The PCM reset will have varing results............
If the car has been running at its optimum a reset will have no effect but a car running poorly (because of tuning, poor fuel etc) the reset will have more effect...........
When you change anything on the engine it will have an effect on the tune, but the car can adjust to cope within a certain range.
But the car can only adjust so far before it shows an error code.
A case in point is fitting headers, cat bypass and catback system will push the cars fuel trims to around 20%-25% and this causes the car to show a code (as a few club members have seen!!!!)
The PCM is always trying to run at its optimum state of tune but will de tune itself if it encounters problems (Knock is the main detuner).
A well mapped car run on the correct fuel will stay in its optimum tune, but if you get some bad fuel it might go off, so when you get good fuel again you can let the car work back upto its optimum tune or a shortcut is the PCM reset.
A little note here when you dyno a car the PCM should be reset or you will get a distotion on the power gain. ie.bad tune car comes in tuner up loads tune (which resets tune) and customer gets larger power gain (not a bigger power figure but a larger before and after figure)
A well mapped car run on the correct fuel will stay in its optimum tune, but if you get some bad fuel it might go off, so when you get good fuel again you can let the car work back upto its optimum tune or a shortcut is the PCM reset.
A little note here when you dyno a car the PCM should be reset or you will get a distotion on the power gain. ie.bad tune car comes in tuner up loads tune (which resets tune) and customer gets larger power gain (not a bigger power figure but a larger before and after figure)
Thats about all I can help with.....but please post if you need any more info.
PS. Most tuners use aftermaket software to access the PCM which you need to pay a license for BUT if you want to use a Hex Editor you can pull the whole OS and reconstruct it if you like..........trust me there is lots to look at!!!!
PS. Most tuners use aftermaket software to access the PCM which you need to pay a license for BUT if you want to use a Hex Editor you can pull the whole OS and reconstruct it if you like..........trust me there is lots to look at!!!!
The learning/adapting is a instant process, so when you reset the PCM the car starts checking to make sure it is running within GM's paramiters straiht away.
One of the many things the PCM checks for is Knock, which in the LSx range of engines is the route to the death of an engine!!!!!
The car works between two spark tables (high octain and low octain)
If the car detects knock it removes timing to stop it and then moves the timing away from high octain table towards the low......
If the PCM detects no more knock in the next period of checking it moves back towards the high octain table, BUT this move back is slow and while it is not using max timing the car is underpowered.
A rough guide would be 4hp per degree on a 400hp engine so if the car removes 5deg (which is not a high number) you have lost 20hp!!!!!!
This situation is sometimes addressed when the car is tuned but not always.
One of the many things the PCM checks for is Knock, which in the LSx range of engines is the route to the death of an engine!!!!!
The car works between two spark tables (high octain and low octain)
If the car detects knock it removes timing to stop it and then moves the timing away from high octain table towards the low......
If the PCM detects no more knock in the next period of checking it moves back towards the high octain table, BUT this move back is slow and while it is not using max timing the car is underpowered.
A rough guide would be 4hp per degree on a 400hp engine so if the car removes 5deg (which is not a high number) you have lost 20hp!!!!!!
This situation is sometimes addressed when the car is tuned but not always.
[quote]PS. Most tuners use aftermaket software to access the PCM which you need to pay a license for BUT if you want to use a Hex Editor you can pull the whole OS and reconstruct it if you like[/quote]
Thanks for answering this one Paul. I appreciate it.
Pay? If it costs more than £1 it's far too expensive.
Using pre-written software takes the fun out of the exercise. I was planning on using UNIX+HEX Editor to look around. Now I've got this info I'll see what I can do about trying to take a copy of the OS/Tune to play with (unless someone can offer one for training purposes).
Thanks again
Thanks for answering this one Paul. I appreciate it.
Pay? If it costs more than £1 it's far too expensive.
Using pre-written software takes the fun out of the exercise. I was planning on using UNIX+HEX Editor to look around. Now I've got this info I'll see what I can do about trying to take a copy of the OS/Tune to play with (unless someone can offer one for training purposes).
Thanks again
Without sounding inflammatory, it is nice to see a commercial tuner sharing hard earned info without charging for it, or avoiding the question due to lack of understanding.
I have learned alot from that thread and imagine a few others have as well.
>> Edited by caspy on Monday 11th July 07:32
I have learned alot from that thread and imagine a few others have as well.
>> Edited by caspy on Monday 11th July 07:32
Just a quick question on this most interesting subject: In the HSV GTS-UK (VTII yr 2000) does HSV provide a basic "tune" which could then be recovered/restored if you did a PCM reset? I am wondering this as after many years of fun (abuse I guess) mine doesn't seem to be as perky as it once was. I am thinking about a "tune" up in the future (wortec) but then after seeing this thread was wondering if a pcm reset might not improve things or at least get me back to where I was in the short term. Finally, is the pcm reset something that can be done via the dashboard cpu/mode buttons?
Hi stevemac,
The PCM reset procedure can be found here:
www.mytired.com/cars/index.htm?page=car_rset.htm
According to what I've learned from this thread by performing the reset procedure you should recover the original maps. Whether it improves things or not could only be known by trying it. I've not heard/read of any bad results from doing the procedure. Just make sure you have read it thoroughly first.
I'd recommend that you have a spare 10A fuse on hand just in case. They can be fragile.
The PCM reset procedure can be found here:
www.mytired.com/cars/index.htm?page=car_rset.htm
According to what I've learned from this thread by performing the reset procedure you should recover the original maps. Whether it improves things or not could only be known by trying it. I've not heard/read of any bad results from doing the procedure. Just make sure you have read it thoroughly first.
I'd recommend that you have a spare 10A fuse on hand just in case. They can be fragile.
I tried just leaving the 10A fuse out for a couple of minutes but the PCM didn't reset until I switched the ignition on and off whilst the fuse was out. I had been running on the low octane table whilst tuning the VE table and it was taking forever to move back to the high octane, only 0.01 for every WOT session ! I had also filled it up with fuel a couple of times, and that didn't make any difference at all, contrary to what I have read on other forums.
So now I am back on the high octane table (verified with HPTuners) and she's much more frisky again
So now I am back on the high octane table (verified with HPTuners) and she's much more frisky again
Gassing Station | HSV & Monaro | Top of Page | What's New | My Stuff