What does the pressure sensor look like? Is it attached to the cylinder or the reservoir?

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1983 Benz 240D - 263,060 (Current)
1983 Cadillac DeVille - 130,000 (Scrapped - Stupid HT4100)
1992 Dodge B350 - 150,000 (Sold)
1984 Mazda 626 - 299,997 (Scrapped)