Heads up. Known ECU issue.


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Heads up. Known ECU issue.

Post by Chris_D »

From a thread first posted on the GT4DC, unfortunately you currently need to join (free) to view threads so I'll summarise on here.

http://www.gt4dc.co.uk/forum/viewtopic.php?f=2&t=5617
and
http://www.gt4dc.co.uk/forum/viewtopic.php?f=2&t=6289

The failure is electrolytic capacitors leaking electrolyte over the board which then etches away nearby copper track until failure occurs.

Symptoms vary, but can be summarised by unpredictable poor running / starting, intermittant flickering of engine light with no stored error code.
The one I directly witnessed would start cold and run fine, but wouldn't re-start when warm and had to be left a few hours to cool down. The owner had reported flickering engine light for a week or 2 when it finally failed.

The latest information is that I have now repaired 2 ECU's which had actually failed, plus a friend repaired his with the same failure. All were rev2 Celica GT4 RC or CS models. I also looked inside a further 'spare' RC ECU and the capacitor had also leaked in that one, but it wasn't showing any symptoms. I have had a report of another friend having seen failure on a couple of rev 3 blitz ECU's (the original toyota part).

The failures I have seen have both been 10uF/50V capacitors, one on the lower board and one on the smaller upper board. The problem could apply equally to capacitors of other values as electrolytics do degrade with age, especially if they are left unpowered for a long time.

Repair basically consists of removing the capacitor after noting which way round it goes, cleaning the corrosive goo off the board with solvent, repairing any broken or suspect tracks with wire links and finally replacing the capacitor with a new one of same value (uF) and same or higher voltage capability. The first thread on the DC shows the repair of one of the ECU's

Lower board showing failed capacitor.

Image

The top board with capacitor removed and after cleaning, showing the missing track

Image


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AManInDandism

Re: Heads up. Known ECU issue.

Post by AManInDandism »

Intermittent check engine light you say? Might need to check this out. Seen plenty burst capacitors, Dell motherboards are notorious for it.

Thanks for the info :th:
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Re: Heads up. Known ECU issue.

Post by MR2DI4 »

Good post but I would add for those who can replace it to do so with a quality capacitor like Panasonic or the like. There is some pretty cheap nasty product in the market these days.

Have got about 3 spare stock ECU's for my Rev 2 so will take a look inside and let the forum know as they have been in storage.

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Re: Heads up. Known ECU issue.

Post by Chris_D »

Agree about the good quality as they are only pennies. Also worth going for low esr. The one on the lower board looks like decoupling on the flyback diodes on the idle solenoid among others.

I have just come across another 2 cs ecu's I think. One was giving symptoms so he swapped to another. Having found capacitors gone, he looked in the other and found one leaking. Again it was the 10uf/50V ones.
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Gaz!

Re: Heads up. Known ECU issue.

Post by Gaz! »

Is this just rev 2 mr2's?


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Re: Heads up. Known ECU issue.

Post by _Al_ »

If this is worse on cars that don't get used regularly then I'll probably drown in capacitor goo if I try to open my ECU...
Red 92 turbo tintop JDM
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Re: Heads up. Known ECU issue.

Post by Chris_D »

It is likely to be worse on cars that are driven infrequently.

There are ECU's out there with capacitors leaked but no symptoms. It is likely these WILL fail sooner or later as the corrosion is a slow process. From looking at the function of the capacitors, it is quite likely the ECU would run fine without them and it is the corroded tracks which cause the failure.

If the board is cleaned and the capacitors changed before symptoms occur it is a much easier fix than having to re-make connections with wire links so I would reccomend people to take the lids off their ECU for a look inside. The capacitors cost pennies e.g. http://uk.rs-online.com/web/p/aluminium ... s/3150805/

So far, I've mainly encountered the failure on rev2 celica GT4 RC/CS ecu's although it can happen to any version sooner or later. Since it's always the same value capacitor going, I'm suspecting a batch problem on the capacitors but these could have been used in many other ECU's from the same era. Again, these cars are old enough to be considered 'end of life' for any electronics so failures such as these are to be expected.
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Re: Heads up. Known ECU issue.

Post by _Al_ »

I'll add it to the list! Thanks for this, great technical advice & could save a few members quite a bit of cash..
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Re: Heads up. Known ECU issue.

Post by MR2DI4 »

Cannot see any of the same type of problems on the Rev 2 Turbo ECU.

The top board has all Tantalum capacitors except for one 100uf 10V at position C500 and the lower board layout is different to the pictures with the only possible 10uF 50V cap at C810 looking all okay. This cap is a Nippon Chemi-Con KMC series so the possibility of a different manufacturer has removed the leakage problem.

There are only 6 Electros in the ECU and I have found that temperature has a big effect on their life, for example they only last 2 years in your TV or Monitor if it is left on 24/7.

If you had issues the first place to start would be a blanket change of all six.

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Re: Heads up. Known ECU issue.

Post by Chris_D »

To update this, it has been reported on the original thread on the DC that someone has encountered 3 MR2 ECU's with leaking caps, so it does certainly seem to apply to more than just the celica CS/RC.

It is almost certainly the chemical damage to the tracks that causes the symptoms rather than the failure of the capacitor itself, so just changing failed capacitors is unlikely to cure the problem. It is vital to clean off any leakage, or it will carry on etching away at the tracks. If you have symptoms, it is also important to test all the tracks which have been attacked and bypass with wire links as necessary.
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Re: Heads up. Known ECU issue.

Post by MR2DI4 »

One of the problems here is that they kept revising the versions of ECU and I'm not just talking Rev 2 to Rev 3. I have all Rev 2 Turbo JDM ECU's and there is at least two different versions in that the layout of the board has changed.

The problem may in fact be limited to just a single revision or even a production run between certain manufacture dates, i.e it was a faulty batch of capacitors.

The ECU's all have a part number on the sticker and an actual manufactured date stamped on the case. It would be handy to know what the dates & part numbers of the affected ECU's were.

If I get time I will open all of mine up and inspect the board, however after all this time I'm not expecting to see a problem.

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Re: Heads up. Known ECU issue.

Post by Chris_D »

My guess is poor batch of capacitors. I'll try to find date codes for as many as possible and post up.
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bustergonadbri

Re: Heads up. Known ECU issue.

Post by bustergonadbri »

hello mate where can i buy a 10uf capasitor.thanks mate bri

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Re: Heads up. Known ECU issue.

Post by Chris_D »

Any Maplin if you don't mind paying through the nose, or RS if you have access (they are normally trade only) http://uk.rs-online.com/web/p/aluminium ... s/2286874/

The critical parts of the job are cleaning off the corrosive goo with solvent and linking across missing tracks as it's the latter that causes the symptoms.
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