Reset/clean the wiring harness connectors on the CEM.

Pretty common cause of Immobilizer - Anti-Skid Service Required on S60s and S40s.
Can cause a lot of other errors ...everything communicates with the CEM.

You will chase your tail forever until you fix this Fully charged unloaded battery voltage is 12.2v. With key/headlights on it shows 11.9v Load tests at 450-500amps I know this is low and that can cause wonky problems but jumping the car or having it on 10 or 50amp charger doesn't help the problem a...

What's the alternator voltage at warm idle? The anti skid 'may' be related to the angle sensor (can try a used one) www.youtube.com/watch?v=idmPhHNNixI For the non start/immobilizer problem, may get some hints on this topic (good to read all posts) https://forums.swedespeed.com/showthread.php?134819...

Look up number of keys fitted in CEM parameters. Could be that key data is lost. Are you using Vida?

Yes the edge connector is on the base of the ECM. There are pink sliders in there that can release the modules but I'd rather use the special tool.

Wouldn't hurt to clean the TCM with electrical contact cleaner while you're in there.

Bosch computer is ECM. The other one is probably marked TEMIC.

Could be mineral deposits (from the water) creating leakage currents.
Wash the board with Electrical Contact Cleaner.

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