Ok.
Then I'm afraid your PNP switch is broken.
A new one from Volvo is usually around £100.
There is a cheeper one made by a company called Scantech, but apparently these are not very good quality and don't last very long.
The job can be done by anyone with a good mechanical knowledge and no specific tools are required, but it is a little awkward, as the car needs to be raised and the exhaust removed. (The switch is located on the outside of the gearbox housing, behind the exhaust.)
Alternatively, a mechanic would charge you about an hour and a half's labour to do the job.
Hope you get it sorted.
Steve
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XC90 V8 Exec, C70 2.4T Convertible, S70 T5 CD, 850 TDI, 2 x Escort vans and a 2.8i Capri.
Clearout has begun, but must continue!