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My guess is that these ECUs would have been a bit more universal than that.
Different markets would have gotten different part nos. How else would you distinguish between them in a warehouse when they all carry the same Bosch and Volvo part nos?
My non-aircon, non-EGR, manual has all those pins present in the wiring loom, but the relevant signals will only mean anything when they're pulled to battery voltage, e.g. by switching on the airconditioning. In my model these are simply tied to ground.
IMHO, these ECUs all started out identical, but the setting resistors and Eprom determined the application (and with it the ECU part nos). In the analog domain signals from the sensors might be different between capacities (e.g. AMM) and hence need slightly different limits (that LM2903 is a voltage comparator).
At the same rpm a B230 will draw in more air than a B200, so the AMM will give a different signal. The Eprom contains the tables for the specific application, B200, B230, turbo, etc, that the manufacturer compiled during engine characterisation and testing.
Over time it's not uncommon to see a design get simplified to save cost by reducing the component count. It will still do the same, but with fewer components. That may be the reason why those ECUs share the same part no but are different inside.
Just for fun I attached a photo of the white label -561 (left) and the -949 (right) side by side. Can you spot the differences?
The Eprom on the -561 did not have a label on it. The hybrid modules look identical.
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