Andy,

I see your quest (and mine to a lesser degree, since I'm not needing a sensor) is still unfulfilled. As you've heard me say before, it seems as if the knowledge is almost kept like a trade secret. Or, perhaps Bendix built the second-source ECU to Volvo's spec which dealt with pinouts (the Bendix and Bosch computers have identical connectors with almost pin for pin functionality) and not necessarily the same means to attain end result.

So, when Bendix chose the Titania sensor, which I believe they did based on the NTK and Walker cross references cited by Steve and a host of others googling for this answer, Volvo had nothing to say about it - done deal. Might have frosted Bosch, if you believe in stuff like that going on in corporate relationships, but I'm guessing Regina exists because Bosch was not up to supplying Volvo's demand one year.

Wish Fitz with his Michigan industry contacts and knowledge would chime in here.

Earlier I proposed a WAG (not even a SWAG) that Bendix may have applied the voltage to the titania sensor that would result in the same stoich crossing point as the zirconia (we know that is Bosch's) produces, which _could_ account for the vague reports of good news using a Bosch universal. Later, finding the curve to be opposite the way I thought in titania sensors, I envision too much design work in the ECU (at the comparator that determines stoich crossover) would be needed to support both types, so I think it was a pretty lame WAG.

I've one Regina in our collection, but unfortunately it is the MIL's 940, 45 miles distant, which she hates to give up for even regular maintenance. I hear (indirectly) she doesn't care for the looks of the loaner 244 I must leave at her house. But maintenance it must have, so I should have an opportunity soon to pull apart the Bendix box and see if anything becomes obvious.

Still, that feature that requires no reference air sounds like it might really improve the life expectancy of the Titania sensor. I know I've killed one Zirconia with outside contamination. Maybe they last so long no one needs to change them, like Chuck says.
--
Art Benstein near Baltimore