[Dave80GTSi]

Now that I know what I was looking for, I found this (appears to be a) TSB via a web search.

Copied and posted here for posterity.

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Printed in Germany – 14, 2003

Note on adaptation

The DME control module must perform a learning and adaptation
routine for the throttle adjustment unit if:
♦The power supply to the DME control module is interrupted
♦The DME control module plugs are disconnected
♦A new DME control module is installed
♦The throttle adjustment unit is replaced
♦The DME is programmed.

To do this:

1. Switch the ignition on for 1 minute without starting the engine.
Do not actuate the accelerator pedal (for instance, make sure
that there is not a carpet pressing on the pedal).
2. Switch off ignition for at least 10 seconds.

The following conditions must also be observed, otherwise learning
is not possible:
♦Vehicle is stationary
♦Battery positive voltage between 10 V and 16 V
♦Engine temperature between 5 °C and 100 °C
♦Intake air temperature between 10 °C and 100 °

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All's well that ends well, I suppose, but I do now find it somewhat curious that I had no such drama recently when I replaced my battery, during which time the battery was out of the car for many hours.