tr Saab SCANIA 900 APC Boost pressure transducer / sensor Up for sale is a good functional Saab 900 Boost pressure sensor / transducer. This is the unit that the APC system (automatic performance control) uses to determine and control the boost level it should provide. this is very often the cause of the problems with no, very little or intermittent boost levels on classic 900-turbo cars, 83 84 85 86 87 88 89 90 91 92 93. If the APC gets erroneous or no signal from this switch, it will typically only allow for "base boost" - about 5 PSI normally. This is certainly not the only potential cause of these issues, but it is one. These are located under the driver side knee bolster.I have tested this unit for correct resistance with an ohm meter and it works properly through it's working range. It will come to you as seen. These are starting to be hard to find in good working condition!