You need to remove the ecu and unplug it to see if any water is bridging the pins, i think they're sealed with rubber tho, if it is soaked then it wants drying thoroughly including the connectors so there's no chance of it shorting as it it's apparently at the moment.
If the faults remain and can't be cleared and you've checked all the fuses etc then you'll need to swap out the pcm for another 1 to discount it.
In the first case i can't see steam cleaning getting to it, more like it has wet the loom somewhere which is shorting but i think just needs a good dry out.
In the second case, if it has fried the pcm then you have to ask, will installing a new pcm (£150+) also get fried due to wet/shorting wiring?
Personally i think you should disconnect the pcm and dry it thoroughly and see if you can get it tested
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