Thanks to the kindness of OOF members: I now have two crank-sensors (one is a 'known-good' on loan as a reference).
The pup-mobile was a non-starter this morning (as expected).......so, I fitted one of the new arrivals, cleared the stored code 19 and the car started and ran well, but something interesting has surfaced upon comparison of the three sensors: mine (the non-starter) was bought new, 5 weeks ago from my nearest VX dealer (Lookers) it was supplied sealed in an official-looking GM parts bag, but seems markedly different in form from either of the two which OOF members have sent me.

Look at the picture below: the obvious difference is the metal 'pip' on the face of the sensor (both similar) which are labelled
Bosch....Whereas, the faulty one I bought at the dealer is labelled
GM Siemens, which has a completely-smooth black face to the sensing head.
Upon measuring the GM Siemens sensor, it is 1.112mm
shorter from the flange face to the sensor face than either of the Bosch units.
...might I have been sold a GM fake/cloned part?

