What's in an ECU? An ECU by any other name...

[Paycheck]

Hey folks,

 

I have what is most likely a stupid question. But as a chronic ignoramus, I'm gonna throw it out there anyway.

 

When getting an e-tune, am I downloading the entire ECU software to the ECU? Or only tune related data (ie. fuel trims, target boost, etc).

 

The reason I ask is...I've been having problems in cold weather and want to get my ECU flashed with the latest and greatest firmware from the dealership (assuming there's an update available - it's an '05 LGT). However, since my car is modded and tuned, I'll also need to download my latest tune afterwards. So will the tune download overwrite the firmware update and basically put me back to square one?

 

Thanks,

$$$

[whitetiger]

ecu is a computer. the computer runs software. a reflash is an updated version of the software, programed for the current state of modification/intended fuel use of the car. any aftermarket tune will negate any OE tune put on by the dealership. if your car is modded already, there is no point going to a dealer for an OE tune calibration. just have a pro-tuner get you set up better for what you have now.

[Paycheck]

ecu is a computer. the computer runs software. a reflash is an updated version of the software, programed for the current state of modification/intended fuel use of the car. any aftermarket tune will negate any OE tune put on by the dealership. if your car is modded already, there is no point going to a dealer for an OE tune calibration. just have a pro-tuner get you set up better for what you have now.

 

I guess I was thinking of it more like a firmware vs. software change.

 

You can upgrade the firmware on your desktop computer without changing the software. You can even update the OS without changing any installed programs. But if I understand you correctly, in the case of my ECU, it's all one and the same. A brand new ECU will be completely overwritten by my current tune. In which case....square one.

[whitexc]

Thinking via type cuz if it was aloud, noone here would hear me....weird things happen with ECU's.

 

In the Fox mustang world the 87-93 ECU's would have a capacitor failure that resulted in the fuel pump not running with ignition input. Solved by either replacing the burned out capacitor or rebuilding the ECU. We have heard here in the LGT community of cooling fan circuitry going awol and running constantly regardless of engine temp. Could it be one of those mystery issues solved by a new/different ECU? You have done a lot in the way of diagnostics. I understand you removed it and kept it inside over night, etc but when the current starts flowing and the resistance starts to....resist....well that's when things get funky. What I don't get is that you say you can fight through the trouble at times and then the car runs great. That's puzzling and would make me think a wiring problem or sensor issue. You seemingly tackled all of that.

 

Just trying to help.

 

Sent from my SM-G996U using Tapatalk

[Pleides]

This would probably be something to ask the tuning subforum because they'd probably know. If you can't do firmware updates via RomRaider then I'd assume a firmware update is a separate thing. You would want to reflash your tune after having a firmware flash, I'd also assume. A firmware flash might change the way parameters are read and *may* require a retune. Regardless, these things are pretty well thought out by the manufacturer using older tech that's been tried and true for several years before it goes into your car. I'd doubt factory firmware would be the source of your problems.

 

I'm pretty certain your dealer will turn away your car for anything ECU-related the second they see its modified anyways because they could brick your car and be liable for it.

[Paycheck]

Yeah, I'm just clutching at straws at this point. I'll try logging data and seeing if something seems out of whack, but it's hard to know what to look for.

 

What it "seems" like is that when really cold, the computer wants to flood the engine. So maybe my AFR sensor is bad and not throwing a code. I believe it's the original one (16 years old at this point). But if it was going bad, why would it perform just fine when warmed up and during summer. Also, I would expect my tuner would have seen some anomaly and raised a flag.

 

Who knows. When I get a chance maybe I'll throw a heat gun on my header and get it nice and toasty before starting.

[Pleides]

If your MAF sensor is appearing bad and you haven't cleaned it, that would be a good place to start. I replaced my original one three years ago and it stopped my check engine light from being on most of the time after I started the car cold.

[covertrussian]

What version of tune are you running? Should be in your tune file it self. AFAIK 2005 didn't have any cold weather fixes, last version is "A2WC522N". If you are not on A2WC522N, you could just flash it to that yourself. Now to me it sounds like your tune it self could be the culprit, so a pro-tuner would need to retune it to fix it.

 

To answer your tune related question, there are two parts of the tune, the Operating System (OS) then inside of that there is the values that run the car (tune it self). When the dealer reflashes the ECU it replaces the whole OS , thus your tune would be completely rewritten and lost.

 

The way we deal with this is, take the current moded tune with the old OS version, then get get the stock tune with OLD OS (that you can get here). To a comparison and note down the changed tables between your tune and stock tune.

 

Next take the NEW OS from the same link as above, and copy over only the changed values. The reason you have to do it like this is, the new OS will have different pointers for data, so a direct Tune comparison wont always work right.

 

It's a manual and tedious process but it's the only way really, especially since newer OS's will have different table sizes, which makes it harder then just a straight copy and paste.

[Paycheck]

If your MAF sensor is appearing bad and you haven't cleaned it, that would be a good place to start. I replaced my original one three years ago and it stopped my check engine light from being on most of the time after I started the car cold.

 

MAF is brand new. Replaced it in the summer when I was doing the other mods.

 

What version of tune are you running? Should be in your tune file it self. AFAIK 2005 didn't have any cold weather fixes, last version is "A2WC522N". If you are not on A2WC522N, you could just flash it to that yourself. Now to me it sounds like your tune it self could be the culprit, so a pro-tuner would need to retune it to fix it.

 

To answer your tune related question, there are two parts of the tune, the Operating System (OS) then inside of that there is the values that run the car (tune it self). When the dealer reflashes the ECU it replaces the whole OS , thus your tune would be completely rewritten and lost.

 

The way we deal with this is, take the current moded tune with the old OS version, then get get the stock tune with OLD OS (that you can get here). To a comparison and note down the changed tables between your tune and stock tune.

 

Next take the NEW OS from the same link as above, and copy over only the changed values. The reason you have to do it like this is, the new OS will have different pointers for data, so a direct Tune comparison wont always work right.

 

It's a manual and tedious process but it's the only way really, especially since newer OS's will have different table sizes, which makes it harder then just a straight copy and paste.

 

Now THAT is exactly what I needed to know! Thanks, CR! I've heard the term "pro-tune" a few times and I'm not really sure what you mean by that. I'm not tuning it myself. I'm getting it E-Tuned by Dynotech in New Zealand. They are one of the recommended e-tuners here on the forums and as far as I can tell, Phil really knows his stuff. I went that route because I have a catless exhaust and the guys in North America that I reached out to didn't want to do it due to EPA regulations. Fair enough.

 

Anyway, this problem predates the mods and tune I did this summer, but Phil told me that the car had already been tuned once before (which I didn't know), so that's what prompted my original question.

 

I'll do some comparisons as you suggest and update when I can.

 

Thanks again!

$$$

[Paycheck]

Ok. Huge WTF here!

 

Just opened my starting ROM in ECU flash to look at the version. It seems the previous owner was doing some screwing around.

 

Original ECU backup shows an '04 Baja Automatic?!?!? Just a tad different than what the correct one shows.

 

I expect the ECU itself isn't even the correct one for my vehicle. Not even sure if I can flash a Legacy GT ROM in to it. Either way, I don't know if flashing the ECU to the latest factory will solve my cold weather problem or not. But I feel like I should regardless. But that means Phil will basically have start over with the tune process. Don't think he's gonna do that for free!

 

So I guess the question now is....if I download the CORRECT factory ECU file just to see if it starts in the cold, can I then put the last modded tune back in and I'm back where I started? Assuming of course that it doesn't brick my ECU altogether.

 

$$$

[covertrussian]

Pro-tune is basically just a tune that was built for your specific car/setup by a professional (or someone that knows what they are doing).

 

Is that the tune that you just downloaded directly from your ECU using ECU Flash? If so then sounds like your ECU might have been swapped out, this is weird but might have been done to bypass immobilizers (My 04 FXT didn't have a chipped key).

 

Keep in mind that ECU's Tune are NOT cross comparable between different ECU's, it's like trying to run PowerPC Mac OS on Intel, your gonna have a bad day. The problem is, the flashing software might not stop you from flashing a wrong OS tune, which could brick the ECU completely.

 

 

If that tune is what was downloaded, Romraider is showing that "A2WC50" is the latest revision. If that's the case, dig up the ECU it self and look at the part number stickers. Maybe someone did accidentally flash the wrong OS hence all the issues that you are seeing.

[Paycheck]

Well, last night when got home I took a chance and downloaded the latest LGT map / firmware. Upon doing so, the car started right up with no issues. It was already warmed up at that point, so I left the default map in there and waited until this morning to try again.

 

This morning, although it wasn't SUPER cold, it still chugged and sputtered away as it normally does. So there's still some other issue at play here that I've been struggling for years now to find. I'll keep looking as long as the weather stays cold.

 

Tuned map is back in so i don't blow something up.

 

Thanks for all the insight.

 

$$$

[Pleides]

You mentioned you thought your AFR sensor might be bad. I could be wrong, but I’m pretty sure that’s your MAF sensor. What part did you replace it with?

 

How is your O2 sensor up front? I’ve had to replace mine once.

 

Is the cold weather issue an idling one?

[Paycheck]

You mentioned you thought your AFR sensor might be bad. I could be wrong, but I’m pretty sure that’s your MAF sensor. What part did you replace it with?

 

How is your O2 sensor up front? I’ve had to replace mine once.

 

Is the cold weather issue an idling one?

 

The MAF sensor is on the cold air intake. It's a MAF and intake air temp sensor combined. That got swapped out in the summer when I was modding the car. I got the part from car quest so it's not a Subaru OEM part.

 

The AFR sensor is on the passenger side exhaust header right before the up pipe. Some people call it the "front O2 sensor" but I think that's incorrect. The other sensor on your downpipe is an O2 sensor and it's mostly to verify that your cats are working correctly. The front one is more for fuel ratio feedback. Anyway, I tried removing it last summer while replacing my up pipe. I was trying to get at the exhaust bolts behind it, but I couldn't get it out. It looks like the original one...seized solid. I ended up being able to get at the bolts behind it by using an open ended wrench and coming at it from the passenger side wheel well with the steering turned all the way to the right. So I never did remove the AFR sensor to get a good look at it. I saw an another thread that (if it's bad) unplugging it will fix the idle issue. You'll get other codes obviously, but it will at least indicate the issue.

 

I tried unplugging the AFR sensor yesterday after the engine was cold to see if it made a difference. It didn't.

 

The cold weather issue is kind of an idling one, yeah. All the details can be found here. See my super long post near the end of the thread.

 

https://legacygt.com/forums/showthread.php/removing-05-gt-camshaft-position-sensor-p0340-263392.html

 

$$$

Edited December 25, 2021 by Paycheck

[covertrussian]

Replied with some ideas in that other thread, to not derail this one.

[Pleides]

NEVER use a non-OEM MAF sensor. You should replace that with the proper Denso part ASAP. Your car will run much better with that.