Restoring the ECU/PCM to default condition
1/6/21 | 10:35 PM
#1
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Restoring the ECU/PCM to default condition
I'm hoping someone can enlighten me on the subject. I'm pretty tech savvy but I've never "tuned" cars before like installing a "BAMA tunner" etc etc.
I got this 2015 Mustang GT PP that runs like crap, excuse my French. BTW it came with no MAF sensor so I bought OEM Ford MAF and installed it but it seems to run A LOT worse - the idle is rough and it surges and stalls sometimes, so I'm running it without the MAF but it still runs bad. But it suggests that ECM reverts to some "default" values when MAF is not present. From my investigation I am 99.9% sure previous owner had a BOSS 302 intake manifold installed in it (its marking is clearly embossed in the underhood liner as it was barely clearing the space). A buddy of mine had it scanned with HP tuners software and the ECU (I guess its PCM in this case) seems to be "corrupted". So I'm guessing they had some sort of tuner installed or had the PCM flashed.
Are most tuners permanently have to be attached or only once to flash the ECU and then removed? What happens when the tuner is removed? Does ECM revert to default settings?
I'm sorry, I know these questions might sound stupid but I have no experience with tuners at all.
I got this 2015 Mustang GT PP that runs like crap, excuse my French. BTW it came with no MAF sensor so I bought OEM Ford MAF and installed it but it seems to run A LOT worse - the idle is rough and it surges and stalls sometimes, so I'm running it without the MAF but it still runs bad. But it suggests that ECM reverts to some "default" values when MAF is not present. From my investigation I am 99.9% sure previous owner had a BOSS 302 intake manifold installed in it (its marking is clearly embossed in the underhood liner as it was barely clearing the space). A buddy of mine had it scanned with HP tuners software and the ECU (I guess its PCM in this case) seems to be "corrupted". So I'm guessing they had some sort of tuner installed or had the PCM flashed.
Are most tuners permanently have to be attached or only once to flash the ECU and then removed? What happens when the tuner is removed? Does ECM revert to default settings?
I'm sorry, I know these questions might sound stupid but I have no experience with tuners at all.
1/7/21 | 12:44 AM
#2
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Joined: February 2, 2004
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From: Insane
Bottom line, TL;DR: Take it to a Ford dealership and get it reflashed correctly. Yes, you'll pay, but the car will be fixed, and fixed right.
--
If they took off the MAF sensor they were playing around with the tune, most likely, or the computer's messed up and this was the 'fix' in as much as it is. The MAF missing will force the computer to go to a table instead and that's why it does what it does.
If they put a BOSS 302 manifold and then took it off, they should have reverted the computer to the old tune. They did not, sounds like, and that is why it's running badly. It doesn't have what the computer expects to be there. These computers are highly tuned for the components in the car, so swapping the intake manifold and/or the intake itself can really screw the car up without changing that tune. Not like the old days of EFI. Hence, my suggestion to take it to the dealer and pay the man to fix it right, the PO left you in a bad state.
ECU/PCM are interchangeable. Engine Control Unit or Powertrain Control Module. Different words for the same thing. You might contact the PO, if possible, to see what they did and if you can get the original tune device to fix it. But I'm guessing that's not entirely possible, so...
Different tunes/tuners work differently depending on how they're purchased, so it's not really possible to say 'this is what happened'. Some tunes are locked to the car when you get them, and the old tune is stored in the device should you decide to reverse the decision. Some you plug in a device and connect it to a phone/tablet, call the tuner up, and they download the new tune in over the internet. Lots of ways to skin the cat. Hence the need to maybe contact PO and figure out what happened and maybe get it fixed that way. Otherwise, you might can pay a local tuner to reprogram the current tune to fix it, but if it's corrupted or such and they can't, then Ford's the place to go, they'll just reset the thing to stock and off ya go. They can also figure out if the PCM's trashed, which is an actual possibility.
Hope that helps. If I'm wrong, someone will chime in soon enough to berate me and then we'll both know.
--
If they took off the MAF sensor they were playing around with the tune, most likely, or the computer's messed up and this was the 'fix' in as much as it is. The MAF missing will force the computer to go to a table instead and that's why it does what it does.
If they put a BOSS 302 manifold and then took it off, they should have reverted the computer to the old tune. They did not, sounds like, and that is why it's running badly. It doesn't have what the computer expects to be there. These computers are highly tuned for the components in the car, so swapping the intake manifold and/or the intake itself can really screw the car up without changing that tune. Not like the old days of EFI. Hence, my suggestion to take it to the dealer and pay the man to fix it right, the PO left you in a bad state.
ECU/PCM are interchangeable. Engine Control Unit or Powertrain Control Module. Different words for the same thing. You might contact the PO, if possible, to see what they did and if you can get the original tune device to fix it. But I'm guessing that's not entirely possible, so...
Different tunes/tuners work differently depending on how they're purchased, so it's not really possible to say 'this is what happened'. Some tunes are locked to the car when you get them, and the old tune is stored in the device should you decide to reverse the decision. Some you plug in a device and connect it to a phone/tablet, call the tuner up, and they download the new tune in over the internet. Lots of ways to skin the cat. Hence the need to maybe contact PO and figure out what happened and maybe get it fixed that way. Otherwise, you might can pay a local tuner to reprogram the current tune to fix it, but if it's corrupted or such and they can't, then Ford's the place to go, they'll just reset the thing to stock and off ya go. They can also figure out if the PCM's trashed, which is an actual possibility.
Hope that helps. If I'm wrong, someone will chime in soon enough to berate me and then we'll both know.
Last edited by houtex; 1/7/21 at 12:45 AM.
1/7/21 | 11:14 AM
#3
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@houtex thank you for the enlightment
Yeah reaching out to PO is really not an option in this case so thats why I'm scratching my head.
If I get a tuner like an SCT X4/SF4 wouldn't that flash the ECU to the correct settings?
Yeah reaching out to PO is really not an option in this case so thats why I'm scratching my head.
If I get a tuner like an SCT X4/SF4 wouldn't that flash the ECU to the correct settings?
1/9/21 | 08:23 PM
#4
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Joined: February 2, 2004
Posts: 7,582
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From: Insane
It might. I'd hate to be spending the money without knowing for sure, which I don't. You can definitely reach out to the tuner *directly* and find out. Don't go to a tuner dealer and ask, go straight to the source and get the info from them. The tuner dealer might just say 'yes' to get the sale... naaah, nobody does such shenanigans, right? 
My take is this: If the car is otherwise stock, going to stay stock, and the tune/computer's ticked off? I'd just go to the dealership and be done with it. If you're going to modify it, then you'll be wanting to deal with the tuner directly anyway, because all bets are off, except in the case that you have to *start* from the stock tune and then they modify that, which I've heard is done sometimes.
Good dang luck, man. PO did ya dirty.
My take is this: If the car is otherwise stock, going to stay stock, and the tune/computer's ticked off? I'd just go to the dealership and be done with it. If you're going to modify it, then you'll be wanting to deal with the tuner directly anyway, because all bets are off, except in the case that you have to *start* from the stock tune and then they modify that, which I've heard is done sometimes.
Good dang luck, man. PO did ya dirty.
5/7/23 | 01:49 AM
#7
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Joined: May 7, 2023
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From: Illinois
[QUOTE=ilov2xlr8;7058922]So I fixed the issue.
I used a Ford IDS in conjunction with a VXDIAG/VCX NANO device I bought off of Amazon to reprogram the PCM and it seems to be working fine now.
Can you please tell me how you did this
I used a Ford IDS in conjunction with a VXDIAG/VCX NANO device I bought off of Amazon to reprogram the PCM and it seems to be working fine now.
Can you please tell me how you did this
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