That little hole on the right side of the switch bank is the cabin temp sensor. When the sensor gets really dusty/dirty, you will need to clean it out. A vacuum cleaner with a crevice nozzle against the small grill should work for a little while.

As to the TRKS switch, it is optional. Your owner's manal says:

TRAction Control System (TRACS) - option on certain models

TRACS is a system designed as an aid when starting/driving off if one of the drive wheels has poor traction due to weather conditions or the road surface and is connected to the ABS control module.

TRACS engages automatically at speeds below 25 mph (40 km/h) when one of the drive wheels loses traction. It disengages automatically when speed exceeds 25 mph (40 km/h). The sound which can be heard when the system is operating comes from the ABS system.


TRACS can be disengaged manually using the switch on the dashboard (see page 27). The indicator light will come ON when the system is off.


Stability and Traction Control (STC) - option on certain models

Stability Traction Control works in conjunction with TRACS to help control wheel spin at all speeds. At speeds below 25 mph, TRACS controls the braking system to stop wheel spin. At speeds over 25 mph (40km/h), the STC system monitors and compares all four wheels. If one of the drive (front) wheels shows any tendency to slip, such as when driving on slippery roads, the difference in speed is immediately detected. This triggers a signal to the engine management system, which will reduce engine torque (by reducing fuel) until the differential is corrected. This torque reduction is handled in stages, and reaction time is extremely fast.

The symbol will flash when STC is actively regulating power to the drive wheels. Normal power may be reduced at this time. This is normal as power is momentarily reduced to help keep the drive wheels from losing traction and spinning.

The STC indicator light will come on:
· When the car is started, for approximately 2 seconds, as the system performs a self-diagnostic test.
· When STC has been switched off using the button on the dashboard.
· If the system is temporarily switched off due to high brake temperatures. STC will automatically restart when brake temperature has returned to normal.
· If a fault is detected in the system. Consult your Volvo retailer if this occurs.