ECU repairs - giving it a try?

[rider]

I have two M/T trac ECU's that have a problem, one permanent on one intermittent but getting more permanent. So what to do, you can buy new old stock ECU's for well over a thousand pounds or they come up on trading sites (from wreckers and modders) for around the £400 now and again or I could have a look see under the hood? Or I could just leave it unplugged. 

I've decided to go delving probably for no reason other than it is something I've never attempted before so I've bought myself a few prying tools to use alongside my hot air gun (if I can find it) to get the glued casing apart. Then if I can see something clearly wrong with a failed component I, as a complete flux core ham, will attempt a repair. Basically, if I do manage a repair then probably anyone can facing the same problem that I encountered. So it should be fun or funny if nothing else. I'll post up pictures as I delve into the mysterious World of failed and failing ECU's so anyone who is remotely interested can witness the fun that I'll undoubtedly be having on and along the way.

I'm in no particular hurry on this so it'll proceed and update as the urge grabs me. It did take me 5 years to de-tyre and refurb a set of OEM wheels so nothing can be taken for granted. But it only took me 2 years to refurb an OEM steering wheel. The trend tends to be once I do start then I tend to get stuck in.

[supragr1]

Hi, Any advice on a HKS F-con VVTI ECU for a Non vvti ? Would it work with a remap on a non vvti ? 

[Swampy442]

I don't think so, for one the loom will be different 

[supragr1]

I took my car to Magnum performance the old Whifbitz Partner and he tried to stick an extra pin in the ECU to make the extra 3 injector pulses from 1 pin? After 2 weeks of trying to get the car started, he made pay extra for a wiring loom bypass harness. He refused to put the wiring loom he messed up back to normal. He still wanted payment. Then he gave the car back to me on a empty fuel tank, all the £30 petrol in the car went in to my oil. The dipstick was 1 inch over the mark and he didn't even recommend  to do an oil change. So no your right the loom is different.  

Edited January 14, 2023 by supragr1 (see edit history)

[rider]

I took the cover off from one of the ECU's today and it's a little disappointing. Everything looks factory fresh with no blown or leaking capacitors or any components that have visually suffered any heat damage. The board looks a minefield to work on with solder joints only 1mm wide. It'll take a pointed iron and steady hand to tackle a lot of the solder joints.

With no leakage the only realistic hope for an 'easy' fix is a dry joint somewhere so I'll take off the underside cover and do some rudimentary resistance and continuity testing with a multi-meter. All the solder joints on the top side that are visible on the components all look shiny and in good condition. 

[Scooter]

 

Easy, but botchy/risky?

https://www.bimmerforums.co.uk/threads/reflow-ecu-in-oven-anyone-done-this-before.426778/

but here it's seen as pointless, but has some good other info 

https://www.bimmerforums.com/forum/showthread.php?2446988-Putting-your-failing-electronic-components-into-the-oven

Edited January 15, 2023 by Scooter (see edit history)

[supragr1]

Mate I obviously on the well known tuners incompetence side . so was the judge when I took darren magnum performance in crews hill north London  the old Whifbitz  partners side to court  . He has made countless endless mess ups on diagnosing my cars , now he just ripped me off for my supra reg  P377 XRH for £80,000 . What has this club come too ? and I quote , (what are you doing as a mechanic owning a Supra . All the other Supra owners don't know about cars ?)

[Style]

Something I've seen people do when repairing laptop and phone boards, when they can't see anything wrong, is spray the board with electrical freeze spray which sort of frosts it up. They then send power to the unit and any shorts will be the first to melt the frost and point straight to any culprits. Seems to be quite good at exposing cracked solder etc.

 

https://www.amazon.co.uk/MOTIP-Freezer-Electronic-Spray-500/dp/B015XMW8A4

[rider]

Thanks for the suggestions. The cooking option is probably a last resort and that temperature requires a high lead content solder to have a chance of being effective. Who knows what lead content solder Denso were using in the 90's?

I've been trawling a few ECU repair videos and it is capacitors that are the usual failure point, followed by diodes. I can see I'm going to need to get up to some kind of speed on electronics to make sense of what does what. There is a video online of a repair on a LS400 ECU that dates from around the same time as Supra ECU's with many common components which is particularly useful as there were capacitors and an in series diode replaced to get the ECU functioning again. What I've learned so far is you cannot test a capacitor in circuit using a multi-meter so I've bought an ESR meter that can test capacitance in circuit, then referenced to the rating that is written on the side of the capacitor. Some bad things can go unseen with capacitors, legs can break below the capacitor due to slight acid leakage or the electrolyte dries out over time and that changes the components capacitance. An ESR meter will quickly (probably not so much in my hands) check the capacitance of a capacitor ruling it in or out as being OK or not.

I'll leave peeling off the lower side cover until my ESR meter arrives. It's coming from China so that'll take a while.

Edited January 16, 2023 by rider (see edit history)

[rider]

The ESR meter has arrived from China, no excuses now. I just need to work out how to use it.

[rider]

Finally got to putting some batteries into the ESR meter and taking the back of the casing. It's micro electronics 90's style in all its glory. A sea of solder points that is so dense its impossible for my eyes to work out which ones belong to the capacitors. It needs a younger pair of eyes to work on this. 

I did scan the circuit board with high magnification on my phone to look for any sign of line degradation or overheating on components. There are a few lines that look brown in contrast to the 'normal' ones that look light green with the film covering.  The brown lines run in between components so there may have been some circuitry overheating but the lines still look intact. As in, none had any clear and obvious breaks. All the components from the mini resistors, to large block resistors to capacitors and chips all look good and the solder looks fine. 

An uncommon failure in capacitors is when a leg breaks. Without the ability to identify which joints belong to the capacitors, especially the smaller capacitors, that is impossible to rule in or out as the ECU issue. 

It really does need a good set of eyes working on it and I've not had perfect vision for 15years now. I tried, but my body says no.

Here are a couple of useful 90's Lexus ECU repair videos I found for reference: