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NorfolkWill
Newbie


Joined: 21 Jun 2019
Posts: 6



PostPosted: Fri Jun 21, 2019 5:39 pm    Post subject: Burnt out ECU - help needed please! Reply with quote

Hi everyone,

I'm looking for a bit of advice on some trouble I'm having with my ECU.

Just for some background:

The car (1998 C2 manual) failed when motoring at high speed and would not restart. The car was recovered and the garage found the ECU was badly burnt out.

They then replaced it with another unit and that also over-heated while driving under load above around 3k RPM (fine at idle) and the same component on the ECU was damaged.

Looking at the images it shows the problem to be with the first transistor nearest to the connector.

I desperately need to know what that first transistor controls in the car as a fault there must be what is causing the unit to overheat and burn. We cannot put in another ECU and risk that being damaged.

Does anyone know or have any more specific information which may help identify the transistor in question? Or some thoughts on the issue more generally?

Thanks in advance for anyone who might be able to help.
Will
 



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MisterCorn
Dijon


Joined: 08 Jan 2011
Posts: 7161
Location: Nottingham, England

2004 Porsche 996 Turbo

PostPosted: Fri Jun 21, 2019 7:00 pm    Post subject: Reply with quote

Trace the track through to the connector if you can, then check the wiring diagram to see what it connects to.

MC
 
  
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deMort
Dijon


Joined: 21 Mar 2015
Posts: 7004
Location: Brighton


PostPosted: Fri Jun 21, 2019 7:06 pm    Post subject: Reply with quote

The black chips attached to the side casing are i believe either injector or coil transistors ..

This is not an overheat as such but a wiring overload / short circuit and im guessing it will be a coil pack .

I can't say which one but from posts here if you have surefire coil packs fitted then they have at times caused issues on 997,s .

MC has already said it .. you need to see which pin in the burnt area leads to which item so its studying wiring diagrams im afraid .

For me though and a guess .. it's a coil pack issue .

Check fault codes if the unit still powers up .. all you need is a code for a misfire to point you in a direction .
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NorfolkWill
Newbie


Joined: 21 Jun 2019
Posts: 6



PostPosted: Fri Jun 21, 2019 9:39 pm    Post subject: Reply with quote

MisterCorn wrote:
Trace the track through to the connector if you can, then check the wiring diagram to see what it connects to.

MC


Thanks MC - I think I know how I'll be spending my weekend!
 
  
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NorfolkWill
Newbie


Joined: 21 Jun 2019
Posts: 6



PostPosted: Fri Jun 21, 2019 9:45 pm    Post subject: Reply with quote

deMort wrote:
The black chips attached to the side casing are i believe either injector or coil transistors ..

This is not an overheat as such but a wiring overload / short circuit and im guessing it will be a coil pack .

I can't say which one but from posts here if you have surefire coil packs fitted then they have at times caused issues on 997,s .

MC has already said it .. you need to see which pin in the burnt area leads to which item so its studying wiring diagrams im afraid .

For me though and a guess .. it's a coil pack issue .

Check fault codes if the unit still powers up .. all you need is a code for a misfire to point you in a direction .


Thanks Ian - appreciate you taking the time to give it some thought.

Do you think it could be related to the fact I've got one cam solenoid on each bank which are out of action? I'm thinking that might be causing the wiring overload / short you've mentioned? Having read another forum post which suggested that transistor was linked to the solenoids, it seems a bit too much of a coincidence to me...
 
  
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toohey
Monza


Joined: 22 Jan 2009
Posts: 191
Location: Naarfolk


PostPosted: Sat Jun 22, 2019 10:56 am    Post subject: Reply with quote

Will

Really sorry to hear about you car - I had been in to visit the garage where it is earlier in the week and they had shown me the first ECU that got smoked.
I'm not sure if the 996.2 ECU (my car) is the same or not but I offered to let them have my car to compare yours to if it helped trace the fault. If the circuitry on yours is too burnt to trace to a pin and the ECU's are the same then the offer still stands. I will drop by in my car and they can compare what they need to help trace the issue....

Obviously they may already have this all under control or the ECU may be different but if it helps the offer is there....

James
 
  
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Luddite
Nürburgring


Joined: 18 Dec 2018
Posts: 412
Location: Scotland


PostPosted: Sat Jun 22, 2019 1:52 pm    Post subject: Reply with quote

OK, OK, so I know nothing of modern Porsches.... But, is it possible to check a wiring diagram to identify the pins/sockets at the ECU for each of the individual (?) coil packs and those of the injectors and check for a low resistance, to identify the coil pack or injector circuit that may be causing the issue..? I might expect signs of overheat on the loom plug/pin...?

Had there been an injector or coil pack issue would this not have been picked up by the data logger..?

Also I guess if nothing shows up it is possible that there could be an intermittent short in the wiring, given the time taken to blow the unit as opposed to it blowing on start up..? But then again that could perhaps be down to the low resistance in the circuit just drawing enough excess current to cause overheating in time.... But looking at the damage caused it does seem like an intermittent short, as opposed to a general overheat... Dunno for sure..

Sorry to read of your predicament hope you get it sorted soon.. Question
 
  
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deMort
Dijon


Joined: 21 Mar 2015
Posts: 7004
Location: Brighton


PostPosted: Sat Jun 22, 2019 3:59 pm    Post subject: Reply with quote

NorfolkWill wrote:


Thanks Ian - appreciate you taking the time to give it some thought.

Do you think it could be related to the fact I've got one cam solenoid on each bank which are out of action? I'm thinking that might be causing the wiring overload / short you've mentioned? Having read another forum post which suggested that transistor was linked to the solenoids, it seems a bit too much of a coincidence to me...


I think you might just have found the fault .. the cam solenoids on early cars can short internally .. in theory it could damage an ecu .. it kinda rings a bell with me anyways .

I would certainly get your garage to have a good look at them either way .



Image of the dme pins ...
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patpending
Hockenheim


Joined: 11 Jun 2018
Posts: 693
Location: IoM


PostPosted: Sat Jun 22, 2019 6:04 pm    Post subject: Reply with quote

The main culprit for wrecking ECU’s to that extent is a bad battery or alternator or fuse links that have been fitted with larger fuses than specified.

Change the battery, alternator and check all fuses when fitting a replacement ECU.

Jasmine porchalink have used ecus or can get them
 
  
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ragpicker
Reims


Joined: 14 Apr 2013
Posts: 4015
Location: North East England


PostPosted: Sat Jun 22, 2019 6:50 pm    Post subject: Reply with quote

Was the car running ok with its variocam solenoids not working? What symptoms did you experience with this?
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deMort
Dijon


Joined: 21 Mar 2015
Posts: 7004
Location: Brighton


PostPosted: Sat Jun 22, 2019 7:34 pm    Post subject: Reply with quote

My understanding of things .. which is in no way factually correct .. it's just how i interpret these systems ..

The dme will usually switch an earth to a unit to activate it with the unit having a seperate 12 volt supply .

If its an internal short or even a wiring short joining the power to the earth the dme supplies then the dme suddenly gets 12 volts shorting to earth internally .

This will generate heat and pretty damn fast .. things can melt .. its down to the speed of the components to switch off the earth feed which is now compromised , flag a code and not try and switch it back on until the code has been cleared via a tester .

Can i just say , this is in milliseconds .

At which point it will repeat the procedure .

i do know that more modern tech can switch faster than older tech .. obviously .. it's not uncommon to get a fault code and a system inop that won't work until the code is cleared .. in other words we tell the control unit its all ok and you can go back to work it then will do so up until it sees the fault again .

Older tech and you may well burn out the control unit .

Sorry for saying a 996 is old tech .. but i'm afraid it is in electrical terms Smile

The vario cam will default to basic setting , it only adjusts when told to .. if you have had the car for years and this failed then you would notice a difference .. if not you may well expect its normal and as such wouldn't know there was a fault .

The dme can also supply a voltage to sensors .. normally 5 volts .. a fault on a single sensor .. a short wil drag down the voltage to all the other sensors on that rail .. a rail being the 5v supply to a set of sensors .. in this case you will get fault codes from unrelated sensors to what the actual fault is , a complicated and time consuming fault to find ..

Been there and done that .. it takes ages and i know full well has caught out an OPC that had to send the car to us to fix ( us being a different OPC at the time ) .. me and my colleague took a couple of hours on that one to track it down ..

Trust me i'm not brilliant and working with another tech makes life a lot easier .. especially in this case .. rare as hens teeth the fault was , ( a cam sensor short that flagged as a throttle position fault ) one of my / our best fixes ever ... credit to my mate for the help .. even though he will never read here ... Matt Thumb

Very Happy

If you use Mid-Sussex for work .. ask for Matt to fix your car .. top notch mechanic .
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MisterCorn
Dijon


Joined: 08 Jan 2011
Posts: 7161
Location: Nottingham, England

2004 Porsche 996 Turbo

PostPosted: Sat Jun 22, 2019 7:49 pm    Post subject: Reply with quote

Check the fuse which supplies the 12v feed to the solenoid in question. Make sure a larger one hasn't been fitted. If there is a fault the fuse should blow. As mentioned, the ECU switches the 0v side, so the ECU fuse is not affected.

MC
 
  
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patpending
Hockenheim


Joined: 11 Jun 2018
Posts: 693
Location: IoM


PostPosted: Sat Jun 22, 2019 10:27 pm    Post subject: Reply with quote

https://www.quora.com/How-can-a-battery-damage-an-Electronic-Control-Unit-ECU

Your ECU has been totally fried and the alternator and battery would always be near the top of my list as the root cause.

The above saves me having to detail why and as well
as the ECU, other circuits can get damaged/fried on the way to the ECU melting down.
 
  
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Avon
Trainee


Joined: 12 Mar 2016
Posts: 79



PostPosted: Sun Jun 23, 2019 3:21 pm    Post subject: Reply with quote

My ECU had to be replaced after a variocam solenoid failure (car is early 1999 M96.01 engine). Replaced both (new solenoid, reprogrammed 2nd hand ECU). No issues in the over 2 years since.

Drivers side cylinder bank. However the car was drivable by disconnecting the solenoid cable, So ECU wasn't dead, but can't recall exactly why ECU needed replacing.

Were your fuses all ok?
 
  
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NorfolkWill
Newbie


Joined: 21 Jun 2019
Posts: 6



PostPosted: Sun Jun 23, 2019 8:08 pm    Post subject: Reply with quote

Thanks for the messages all - it's great to know there are so many people out there are willing to help however they can.

So, we're going to go down the route of replacing both variocam solenoids, and seeing if that does the trick (which I'm pretty hopeful it will do), given the burnt out pin in the ECU connector (no. 25) is responsible for camshaft adjustment, and the pin correlates to the burnt out transistor in question. which too is related to camshaft adjustment. It's all pointing towards the world's most expensive solenoids!

Luckily, the mechanic stopped the test drive short (having thought they had solved the issue by changing the coil packs), of wrecking the replacement ECU unit (although there was some burn damage to the same transistor), so it should act as a useful guide for a test run once the solenoids have been replaced.

I've managed to pick up a second replacement ECU for £180, but I'm hopeful with some careful micro-soldering and a replacement transistor that the slightly burnt replacement unit can be fixed.

I'll keep the thread updated on how I get on over the next couple of weeks.

Cheers,
Will
 
  
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patpending
Hockenheim


Joined: 11 Jun 2018
Posts: 693
Location: IoM


PostPosted: Mon Jun 24, 2019 10:11 am    Post subject: Reply with quote

I don’t think these can be reprogrammed so you may need the other gubbins as a kit(ie DME immobiliser keys) from the same donor car as the ECU is matched to those other parts and to the cars VIN.

You also need the proper Porsche diagnostics tool to re-flash anything.

I’d never try to repair any slightly burnt ECU when for 400/500 quid you can buy a used set of matched electronics vs spending hours or days trying to get it to run.

You may only end up spending more money and pulling your hair out in the long run.

https://www.ebay.co.uk/sch/i.html?_nkw=Porsche%20996%20ecu%20&ssPageName=GSTL
 
  
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deMort
Dijon


Joined: 21 Mar 2015
Posts: 7004
Location: Brighton


PostPosted: Mon Jun 24, 2019 7:34 pm    Post subject: Reply with quote

You can only swop a second hand ecu if you have the IPAS codes for it , even then its a bit of a fiddle .. DME and alarm control units have the same immobiliser code .. you need the chassis no. and V5 of the donner vehicle if fitting just a dme basically to recode it .

If you are just using it for spares to repair your old one then its fine .

bank 2 cam solenoid seems to be the fault , pin 52 i would expect is at the other end of the plug so not at fault ..

As these are not cheap to replace then perhaps bank 2 only ... i'm also not sure if bank 1 can be replaced with the engine in situ .. the garage will say ... i'm pretty sure that one of these banks needs the bracket removed / engine drop to replace either way .

I'll just add .. there are some amazing people on this forum that will help as much as they can Thumb
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Ghianightmare
Spa-Francorchamps


Joined: 25 Apr 2017
Posts: 346
Location: Dublin


PostPosted: Wed Jun 26, 2019 9:55 am    Post subject: Reply with quote

So we have an intern in my office at the moment - an electronics engineer and software engineer. Basically a genius. He was in LA last year with an Irish team who qualified for Elon Musks Hyperloop trails... Look it up if you haven't heard about it!

Anyway we were chatting away and he was telling me that most of the time electronics fail are because of capacitors and how he fixed a €400 C Class Merc gearbox ecu by replacing the 12 cent capcitor...

So i showed him the photos above and straight away he started talking in a language that I only partially understood (mosvet transistors etc)- but essentially he said (only having looked at the photo) that either the battery is stuffed, or alternator voltage regulator was gone or faulty, or the demand component (bank 2 solenoid) was faulty. Which correlates to what others have said above.

he's said that fixing either of the ecu's in the photos is not realistic - it could be done in theory but you would be chasing faults forever on it).

Hope you get it sorted
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patpending
Hockenheim


Joined: 11 Jun 2018
Posts: 693
Location: IoM


PostPosted: Wed Jun 26, 2019 10:40 am    Post subject: Reply with quote

Whip the alternator out and change out the brushes and regulator.....costs buttons and you also have a refurbed alternator. A new battery is less than 100 quid with a 3 yr warranty.

Your biggest cost is the ecu kit/gubbins lifted from another donor car otherwise to try to do it any other way is going to be grief stricken, costly and time consuming.

Give a respected Indy like Jasmine porchlink or 9m a call as they may have the electronics to do the job and will tell your guys exactly what they need for the transplant. They will need all the sticker details from your existing ECU.
 
  
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RXBoxster
Monza


Joined: 31 Jul 2015
Posts: 216
Location: Preston - Lancashire


PostPosted: Wed Jun 26, 2019 12:03 pm    Post subject: Reply with quote

Ah, I think I have supplied you with 2 ECU's

Looks like you might just have a short somewhere? or wire corroding/bad earth?
 
  
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