ECU codes

[Freaky Beanie]

Ohh so it's input not output. Glad to be protecting my ecu then. Ohh and my model if 89 is manufactured in 04/89 Japan.
And the ECU had minor damage to the trace. Cleaned it and made the trace again out of solder.

sure.
all caps like this have but one purpose they are filters. (electrolytic, mostly) In electronic parlance it's "a bulk filter cap."
it's not optional at all, in fact nothing there is optional. (save, maybe one output port , ill not mention optional smog parts or ports....)(
That corner cap is the most key of all, and the most likely to fail. 1000s have.... now....

it filters out all those huge noise spikes the cars electrical system has. (capacitor oppose a change in voltage! and are why they are used for filters)
up to 100volt spikes, say from the a/c clutch going off line, and BAM. and other.
there are many inductive noise sources on cars, and is a problem (ask Ham radio operators mobiles) {relays, VSV , solenoids, injectors, ISC coils, and more.. even the starter solenoid)

if the cap is dead, the spike hits the regulator, and may do one of 2 things,
1: blow the REG CHIP up. Most IC's just hate 100v,spikes.
2: cause it to reset. and if IT resets, the CPU (processor ) resets, over and over, in most cases. The rubycons have all failed now.... seen only one that was good, in a ECU parked on self for 25 years.
of this era....

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doing repairs under this cap , is not easy at all.
and depends on level of damage
here are some levels
just green slime there, clean it with bicarb, and put in new cap, ready to rock.
green stat too long trace damage top, ok , bicarb it , and fix traces , new cap, done.
then the green gets deep, way deap and wrecks both sides, can be fixed,sometimes.
and last it burns up. the cap shorts, the green causes the PCB to burn. helps it. and is mostly hopeless.
damage has no limits. and many parts on this PCB are not sold anywhere.

best is to always have 1 spare ECU, they wont get easier to find, nor fix at all in the future.
if lucky you can find a used one for 50 bucks, most places have scalping prices. like $500
find a person selling. one that is just regular person, (on fleabay 9 of 10 are the scalpers. it's there prime territory there) the price is the key clue.