Volvo 2002 v40 p0600 error code. where is reset button

Loss of Serial Communication Link

http://www.autocodes.com/p0600.html

Could have many causes, but a good start could be to have the
oxygen sensor voltage output checked.(In exhaust system)
This would explain why mixture/ variable idle speed occurs.

No there is no reset, if a problem exist in the engine control system then the light will stay on until it is fixed.

p0600 is a generic code. it could be several different modules. are there any status messages that come with the code to identify the effected modules?

P0600 is the loss of serial communication link. Generally this is a problem with the wiring in the OBD-II or between the ECU and the connector. Of these is a fault in the ECU. Do you recive any other codes?

P0480 Cooling Fan I Control Circuit Malfunction P0600 Serial Communication Link Malfunction not sure what they are on a Volvo,, repair wise, but thats what the codes are according to my research

agree, idle control valve is a stretch. I would check the EGR valve for proper operation and clean the hoses if they are dirty. If not that, maybe the MAP sensor is off. Does it cut out when you open the throttle or even when you just stop at the intersection?

replace lambda probe expensive but it will run ok after that, i dont know if you know how they work so here's a brief: lambda tells ecu how rich the exhaust gasses are, ecu ajusts fuel input as neccasery eg lambda says not anough fuel ecu puts more in and the other way round.
so if your lambda is covered in **** when you get it out just clean and put it back, if it looks clean enough it needs replacing!! jezza

We had the same problem and found it was the fuel pressure regulator. Upon replacing it no longer gives any hesitation at startup.

Leave the stereo on constantly for 2 hours with the key in egnition but engine not running. After 2 hours the stereo will reset and the OFF will change to CODE.