What the hell is a Misfire Correction Factor and why should I care? Exactly my thought as well – and as soon as your DB9’s battery goes dead or is disconnected for service work, you car will forget this critical engine tuning data and then you’ll care.
What makes this a bit more confusing is that the issue is described under many names, but all referring to the same thing:
- Misfire Correction Factors
- Coast down procedure
- Adaptive Learning Procedure
- Flywheel Learning Procedure
How Aston Martin Describes it
The Engine and Transmission Control Modules use an adaptive learning process to improve performance by compensating for manufacturing tolerances in the engine and transmission. Benefits include:
- More accurate misfire detection
- Improved engine emissions
- Smoother gear shifts
The adaptive learning procedures are required when either the Powertrain Control Module (PCM) or the Transmission Control Module (TCM) have been reprogrammed or have lost their ‘Keep Alive Memory’.
The following procedures will therefore enable the Control Modules to ‘relearn’ the relevant data if lost following service work during which keep alive power that has been lost. The original data would also be erased from the controller memory if any Module has been ‘reflashed’.
A Technical Description
Grant Neal writes about it this way in his excellent book “The Definitive Guide to the new Gaydon Era Aston Martin”:
A new engine management system (Spanish Oak) was also introduced, unveiling another new advanced feature called a ‘neural net misfire detection system’. Ford had been working to bring this JPL NASA developed technology to their cars since 1998 and the DB9 was to feature the fist on-board neural network in an engine control module. Craig Stephens, manager of Research and Advanced Powertrain Controls at the time of the 9’s launch (2004) provides further information in his official press release: “The DB9 was quite a challenge because of its V-12. The engine frequency of firing events is so high that the legislative requirements for the misfire detection could not be met with conventional computing resource. Neural networks offered us a whole new paradigm for computing and the potential for a misfire detection system that would be fully capable of meeting every detail of the regulation.” He continues, “Unlike traditional computer system that need to be programmed for each step, neural networks are programs modelled on the way human brains learn and adapt. The DB9’s module keeps tabs on engine combustion performance with a sophisticated software program that compares actual engine performance to design specifications. The designers build a critical threshold number of misfires into the system. Once the neural network detects the critical number, the Check Engine light is triggered and the misfiring cylinder is shut down to avoid damage such as a melted catalytic converter. We now have the most complex vehicle application of a neural network in the world.”
There is also an excellent article online published by Ford that goes further with explaining what Craig Stephen’s was describing above. Worth a quick read if you like to understand how cool the DB9 is.
How do you know you need to relearn the Misfire Correction Factors?
It was during my recent trip to my local dealer to have my engine software updated I learned from Tim (a certified Aston Martin Master Technician) that my car currently had NO misfire correction factors and that the learning procedure must not have been done after some previous service by the DPO (Damn Previous Owner).
Tim also explained that the engine would have been operating on a very rudimentary set of parameters while awaiting someone to tune it. He encouraged me to follow the process below whenever I could manage it.
The Misfire Correction Factors can be accessed by a service technician using the AMDS (Aston Martin Dealer System) computer linked to the car. If the Dealer is going to disconnect the battery for service work they backup the correction factors, and then restore them afterwards. Great, as long as you have a $15,000 AMDS handy.
The sad truth of it is that us DIY guys have no idea if the engine has no codes and is running in default mode, or if it has codes. Normally there is no way to tell without using the AMDS system. [UPDATED March 27, 2016] I’ve learned how to determine if the Misfire Correction Profile IS or IS NOT Learned using my Autel MaxiDiag MD802 OBDII Code Reader. You can check out my blog post on using an OBDII code reader and how to read the Misfire Status in my other post ‘Getting More information with your OBDII Reader’ for more information on this.
When do you need to relearn the Misfire Correction Factors?
As noted in my other blog posts on Seat Calibration and Window Calibration, the engine PCM’s also use the type of storage memory (‘Keep Alive Memory’) that instantly erases if power is removed even for a moment. So if you have a low battery, dead battery or service event that causes the power to the PCM to be interrupted, the calibration will be lost and the factors will need to be relearned.
This could happen if your Dealer reflashes (updates) the PCM software.
Another condition in which you will want them to be relearned is if you do service work that replaces the Coil Packs or Spark Plugs. Since these are the an integral part of the engine ignition system that the Misfire Correction Factors are designed to optimize, if you change them you need to re-calibrate to get the full benefit of your hard work.
The short answer is that if you’ve had a dead battery or disconnected your battery for any reason, you can be assured the memory is lost and you should do this procedure.
How to relearn the Misfire Correction Factors
Surprisingly I’ve been unable to find any documentation of the procedure in the Official Aston Martin Workshop Manual. The need is foreshadowed, but the process is not explained:
“After connecting the battery, the radio preset stations and the door window controllers will require to be reset (Adaptive learning data in the PCMs and TCU (Auto transmission) modules will require to be re-learned by driving the vehicle for some miles in a range of driving conditions), drivability may be slightly compromised until the vehicle systems have completed their adaptive learning routines again.”
Aston Martin released Service Bulletin SB148 “Flywheel and Gearshift Learning Procedures” in November 2004 as the issue is so common. You can read it here.
I’ve also received inspiration for this article from a forum post over at 6Speed as well as others.
The process is simple, but the hardest part is finding long enough stretch of open road to perform the steps. Essentially you get the car up to speed then coast for a long while several times in a row, and the ECU is closely monitoring how the engine ignition is working during the zero throttle coasting. Don’t ask me how, but it does.
- Be safe – at times you’ll be coasting along an Interstate Highway at just 20 m.p.h. so plan when to do this so you aren’t out in traffic. I tackled it at 6am on a Sunday morning.
- The car needs to be up to normal operating temperature. Be sure to drive a few miles before you start the process.
- Turn off the Air Conditioning. It will NOT re-calibrate if you have the A/C on. I turned my climate control know to the OFF position entirely.
In a Touchtronic (automatic) car, make sure you are NOT in Sport mode, or paddle shifting. Just have the car in normal Drive (D) mode. In a Standard (manual shift) car you can just do the procedure in 6th gear.- On a long, clear, flat open stretch of road accelerate normally to 70 m.p.h. and cruise along in 6th gear then let off the throttle completely and coast down to 20 m.p.h. without touching the brake or the throttle. If you do, this aborts the learning process and you need to start over.
- When the car reaches 20 m.p.h. accelerate normally again to 70 m.p.h. and repeat step 5. Remember you can’t use the brakes AT ALL during this procedure.
- Do this coast down procedure a total of 5 times [see my update on this below].
The really unsatisfying part is you will have no indication that its worked (or not). Blind faith. The next time you are at the dealer you can ask them to check (and save the codes to the AMDS if it did work). [See my update on this below]
[UPDATED March 27, 2016] I’ve learned how to determine if the Misfire Correction Profile IS or IS NOT Learned using my Autel MaxiDiag MD802 OBDII Code Reader. You can check out my blog post on using an OBDII code reader for more information on this. But, after I followed the coast down procedure above and hooked up my code reader and looked at the Live Data indicator for MP_LRN(Misfire Profile Correction Learned), the value was set to YES. See the photo.
My mechanic Tim told me the official factory procedure describes 70 to 40 just 3 times, but his experience has shown it might need a little longer time coasting and a few more tries, so he suggested 70 to 20 for 5 times. If I’m going to do it, I just want it to be done.
[Updated January 17, 2017]
I had to relearn the profiles on my car again recently since I changed my Coil Packs and Spark Plugs. When I did it this time I decided I would have my OBDII Code Reader hooked up ‘live’ within the car and watch the Live Data field (noted in the update below) and see when it actually decided the profile was learned during the procedure.
I followed the learning procedure, and to my surprise it was learned after just ONE coast down from 70 to 20 mph. I saw the live data value change from NO to YES. No need to do four more coast downs [Sweet, since this needs a really large gap in traffic]. I suspect this might vary on the condition of your engine and what the computer thinks, but it could also be that they are just being super conservative and suggesting to do it multiple times since you normally wouldn’t have an OBDII reader attached giving you the live play-by-play. So, if you have one, I’d say modify the procedure to watch your live data and do the coast downs until the value changes to Yes. If you don’t have a reader, then I would say still do the five coast downs to be sure you get it done.
I’ve created a simple video of me doing the procedure if you’d like to see me out driving at 6am in the dark on Interstate 5 north of Sacramento, desperately in search of a long and clear enough stretch of open flat road. It seems like forever to coast down. Have a look…
Aston 1936 
Muy buena nota.
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Thank you Jorge!
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Very happy to discover your website Steve! Ive had my 07 DB9 for a few years and choose to do as much of the maintenance and repair as I am able. Your information is really helpful and appreciated!
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Great info. I did the procedure after changing spark plugs, coil packs and bad injectors. Fortunately I live in rural south Texas and there’s plenty of long country highways out here.
J
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Hi Steve,
I, in common with many other DIY Aston DB9 owners, greatly appreciate your excellent videos that help us to maintain our chariots, you undoubtedly put a great amount of effort into both the work and the video production. On behalf of all …. thank you.
I am about to undertake “the changing of the plugs and coil packs” having developed a misfire on Cylinder No.3 according to the live data on my OBDII reader as being 681 misfires in a given short period. Cyl No 9 = 88 and Cyl No 10 = 110, the rest being in the range 1-17 misfires. My DB9 is like yours a 2005 MY mine has completed 35,680miles.
I intend to replace all 12 plugs and coil packs as you did …… but now to my actual question. I have read with interests your “Relearning the engine misfire correction factors” and the need to coast down from 70 to 20 MPH a number of times. I am fortunate to have a two post car ramp in my garage with arms that extend under the car to lift it for undertaking work. Do you think I could undertake the coasting exercise with the car say 12″ off the ground? in this way I don’t need to find a long stretch of road. Do think all four wheels should be on the ground and rotating as in your procedure to give some rolling resistance to the slowing down procedure.
I would be interested to hear your thoughts. Have you heard of anyone using my idea?
Best regards,
Mike
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Hi Mike. I am jealous, having a ramp would be a nice addition.
I don’t think you can simulate it. The dealers don’t, and they have ramps. I think the transmission and engine need the represenatitve engine and drag loads, and I can’t imagine simulating those without a sophisticated dyno. I know on mine the transmission is in a learn mode too, and is figuring out the shift points and patterns. Best to follow the whole procedure I think, as much of a hassle it is. The last time I tackled the event it just took two tries to relearn it, I was using my OBDII reader to watch the live data and the bit that says whether its learned or not. If you don’t have an OBDII, then I would do the whole process.
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Hi Steve,
Thanks for the reply and I’m sure you are correct about needing all the wheels on the floor! In the UK we have the MOT (Ministry of Transport) test every year on cars over 3 years old and for that test they have a rolling road to check brake efficiencies etc. perhaps that would be another way of doing the “coasting” setup. That said I wouldn’t like to think of doing 70MPH on one …. what could possibly go wrong !!!
I’ll find a quite bit of road like you did and leave my OBDII connected I think.
Mike
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Hi Steve,
I’m trying to think of the proper accolade for your website, inspirational comes to mind though that’s not quite it 🙂 I discovered it while trying to determine why the passenger seat adjustments had suddenly stopped working. Excellent web design and full of information and links that are a valuable supplement to the AM service manual for those of us taking personal care of our vehicles.
Resetting the seat module was the fix and then I realized that resetting the window module would eliminate the wind noise that had recently developed, Both indicative of a weak battery which is my project of the day.
Regarding resetting the misfire corrections: I do have a road in mind that could work for the coast down procedure but was wondering if it could be done on a chassis dyno with the manual transmission DB9? Bonus would be see what kind of power is getting to the wheels as I replaced the engine with a fully remanufactured AM unit and added a Quicksilver exhaust.
Thanks again for keeping up this excellent resource.
Paul
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Glad the information is helpful. I’m pretty sure the coast down needs to be done on road to get the full benefit as it learns your driving style, etc. Hopefully the new engine and exhaust sound great!
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In lieu of road calibration or a dyno, I suppose putting the rear end up on secure jack stands and doing the coast down procedure in the garage would be ill advised? Though might it work without any resistance during the coast down?
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I really think it needs to be an on the road experience. Even if it worked technically, I’m not sure that’s what the computer is really trying to learn.
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Thanks Steve. I’m headed out now to do the engine calibration. For those near Harriman State Park, North of NYC, Route 293, rolls through the West Point military complex and offers long straights, excellent visibility, light traffic and a wide shoulder should you need to let someone pass during the coast down. Also a great area with twisties for your car or bike and some good eateries nearby..
The DB9 sounds great out of the box, but with the Quicksilver exhaust, OMG – as good as it gets! The remanufactured engine, came as a complete running unit with everything new and uses a heat seasoned block. Seat of the pants, I think it’s making more power. I replaced the clutch at the same time with new, and while I can’t detect any slippage, under sustained WOT, I can smell the clutch a bit :). It was quite impressive to see them change out the engine. There is an enormous jig that lifts the entire body off the frame.
I purchased the car used with 20K miles in Atlanta and asked my youngest son who had just gotten his license if he wanted to fly down and help me drive it back. Did his eyes light up! Quite the road trip, coming North through Blue Ridge Parkway and Skyline Drive. Once home I had detected what seemed to be a valve train noise. After three dealers couldn’t find the source, we decided it might be a main bearing. I had a few months left on the partial warranty that came with the car so I decided to go for the new engine and did the clutch and exhaust as well.
I don’t have an OBD reader so I rely on faith, but either way it should be a nice drive.
Thanks again for so much great info.
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So I have faith that my misfire corrections were learned though I only got 3 good passes. I couldn’t get to Route 293 as access through Route 6 was totally bumper to bumper. I’m guessing, holiday weekend shoppers headed to Woodbridge Commons Outlets. So I did a quick U-turn into Harriman to find some curvy roads and found myself on Lake Welch Drive … This could work, and it did. No traffic, the uphills seemed to be just right for expediting coast down 🙂
Unrelated: Anybody have advice on upgrading the navigation and sound system? The DB9 is my perfect dream car. However, the controls to open the Nav, decided to take a permanent vacation and service said $4k to fix, and we agreed probably not worth it. My somewhat perfect fix would be to get the larger iPhone and mount it in place of the OEM Nav and manually fix it in the open position. If I can get power to it and connect it to the sound system – Voila, updated navigation, Waze to keep track of the patrols and all my music! Maybe, I could even cut a discreet hole in the Nav cover so I can have an on-board camera!?
Enjoy the weekend!
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Regarding the nav system, I discarded the Volvo junk from 2005 DB9 as soon as I bought my car. I replaced it with a Garmin Nuvi 2699 with back up camera and an auxiliary camera in the grill so I could see curbs when I park. I retrimed the plastic surround to retain the Garmin with some silicone to hold it in place. Reconnecting the harness to the nav popup allows it to come up when I start the car and go back down when the ignition goes off. Works perfectly, provides front and rear view, has cell phone connectivity, traffic alerts, and great navigation capability. And it is physically indistinguishable from original – except it works. Reply to my email and I will send a picture of it.
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I have just purchased a 2007 Vantage and would really like to make the same modification.
Please send Photo
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Please send photo
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Hi. I think I’ve seen people mounting a modern Garmin unit in the same space, and it’s touch screen. I’ve also see some fancier installs where your own phones Screen gets duplicated to pop up screen, so essentially your whole phone (texts and all) are onscreen. You’d need to have the Bluetooth audio option for this. I haven’t got a link for it, but I think it was on YouTube somewhere. Let me know if you find a solution and how it works
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What would happen if I replaced the battery after first connecting a 2nd battery to the cables to keep the system running? And then taking off the connectors of the battery, replacing it, connect the connectors to the new battery en finally disconnect the 2nd battery from the cables to the first battery.
Would that help to not to have to relearn the misfire correction?
Joris
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Hi Joris. This depends on what you are trying to accomplish. If you are merely trying to change your battery without loosing the cars settings, this approach might work OK if you are very careful not to short something out. If you are doing a coil pack change (like I was) you actually really want to go through the relearn process because you’ve changed a part of that system.
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Hi Joris, I wouldn’t be afraid of completely disconnecting your battery the prospect of relearning sounds worse than it is. You are not going to do something that will stop your car from restarting and you only lose a few settings. Steve has blogs to show you how to reset them. The relearning process 70-20MPH is surprisingly easy to achieve once you find the best bit of road to try it on. The car seems to run OK even before you “re-learn” it, the learning process takes the car to the optimum performance settings but it still runs great even before you do it. I think you run a risk of jump or connecting cables falling and shorting out and that would be a bit of a disaster as you could do harm to some of the electronics.
Take a deep breath and disconnect …….. promise it won’t hurt !!!!!!!
Mike (Aston #2209)
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I have a 2005 DB9 and I tried the coast down procedure with the ODBII reader attached without success. I did 4 runs, each run consisting of four 70 – 20 coast downs ( that’s all the road would allow). In retrospect, I did put on the flashers when dropping down below 40. Do you think that would have a negative effect on the test?
Thanks for all you good work on this site.
Paul
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Hi Paul. One of the tricks to it is you have to have the AC turned completely off else it won’t perform the correction. I don’t think the flashers would have mattered.
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Steve, Thanks for getting back to me. I did have the AC completely off, as well as the Sport Mode not engaged. Also, no codes were thrown during the test. I even disconnected the battery, sat for 5 minutes before reconnecting it, and then ran the 70 -20 sequence again. Could not get the Misfire Correction Learned factor to switch to YES. And, to top it off, yesterday I took the car to Aston Martin in Palm Beach, explained the situation, and was told they couldn’t help me, i.e., they weren’t interested in looking at my car. Anyway, any suggestions will be gracefully received.
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Hi Steve,
Just finished changing coil packs and spark plugs on my ’07 DB9 following your videos. They sure are a lifesaver! There were a couple things that I thought would be interesting to share from my experience for anyone else taking a crack at it.
You noted that removing the passenger side fuel rail first makes it much easier because of interference from the temperature sensor. It looks like sometime between ’05MY production and ’07MY production, not only did AM change from 2-pin to 3-pin coil packs, but they must have moved that sensor. Makes no difference in the procedure, but thought it was interesting.
Also, looks like on later MY DB9s, AM added little clips to the fuel injectors to keep them attached to the fuel rail. It’s an added step to remove them, but pretty simple to just pop the metal clips back and wiggle the injectors free. Of course, reaching the two furthest back injectors to get the clips off was a challenge, so make sure your magnet is ready to grab the clip that will undoubtedly shoot off and land somewhere in the engine bay! (Unfortunately speaking from experience here).
Finally, if anyone has read your blog prior to purchasing an OBDII reader, and chosen to go the route of the Foxwell tool (I got the NT530, which is the same thing just the current iteration), you’ll find that in the Aston Martin specific software, there are a lot of modules you can tap into, but they aren’t exactly intuitive. The one I wanted to highlight (and the reason I’m posting this here) is the “Misfire Correction Factors Learned” is buried in the 8-cylinder ECU module (which made me scratch my head at first). Once you open up that module, and go to live data, the field you’re looking for is “36-1 profile correction learned.” With my tool hooked up, I did the coast down procedure as described, and on my second coast-down, at around 40 mph, that field changed from “Not Learned” to “learned.” Success!
Sorry for the long winded reply, and feel free to delete and move this information somewhere else if you see fit. Just wanted to say your videos and blog posts have taken a lot my worries about owning an Aston Martin away, and have boosted my confidence to work on it myself. I hope other readers find this info helpful like the rest of this site!
-Michael
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Thank you Michael. This was very helpful.
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Does this process apply to DB9 from 2008 to 2010? I would like to think AM would have improved the engine management system by then.
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Yes, its the same. Good luck!
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Yes, exactly the same. During the great recession hardly any actual development went on.
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I just completed a new battery install on my MY13-DB9. I hooked up my Foxwell NT520 and it’s reading the “P1000/Active – System check not completed since last memory clear” for 8 cyl. ECM, 12 cyl. EMS-P (ECM Bank 1) and 12 cyl. EMS-S (ECM Bank 2). I turned off Sport Mode and the AC and completed 5 successive 70 – 20mph coast downs without touching the throttle or brakes. Returned home and reran the diagnostics. I still have the P1000 code on 8 cyl ECM and 12 cyl. ECM Bank 1 but not on 12 cyl. ECM Bank 2. However when I go into live data all three reflect “36-1 profile correction is learned”. My question is why am I still getting the P1000 code if the profile correction has been learned?
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Hi Steve. Its good that you got the 36-1, that means the Misfire Factors are now learned. The P1000 can be ignored. After you clear the codes from the system, the system sets a P1000 which means that the drive cycle for the car isn’t fully learned yet (since the code clear tosses some of the settings). This will happen automatically over a few days of driving. More or less its checking on the O2 sensors and Evaporative control system to be sure they work, etc.
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Thanks Steve. You are correct. I drove the car a bit more, rechecked the system and the P1000 codes wer gone.
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Thanks Steve, can you please let me know if on a manual car do I have to gear down or just put it in neutral?
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In a manual car the process is the same, except you leave the car in 6th gear the entire time. Don’t touch the clutch. The idea is for the driveline to be coasting down all together under load. Just stay in 6th the whole time. Let me know how it goes.
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