Volvo Repair: acu on V40, bosch car service, service reminder

Question
I have bought a second hand Nov 1999 V40 which has developed a fault, this appears to indicate the car having a max temp reading on the dash even when the car is just started from cold. I suspect the problem is the ACU and is due the battery having failed. How can I cure this problem. Also how can I clear the service light from the dash.  

Answer
Hello,
to clear Service reminder lamp is not possible from driver info module, it can be with VADIS, Volvo Aftersales Diagnostic Information System, or Volvo System tester, or any Bosch car service.
About outside temperature, I think outside temperature sensor has faulty, try to remove it and clean it, maybe it will start to wrok again correctly, if not it should be replaced with new one. It is located in the front fender, you can reach it from topside of fender after opening the front bonnet.
Regards...