I posted back in Oct '18 about my car, a 1.6 manual X reg 2000 V40, which appeared to be a mk 1.5 since whilst the reader would report I had an error code it wouldn't show me the exact code nor let me clear it.
https://www.volvoforums.org.uk/showthread.php?t=287414
https://www.volvoforums.org.uk/showthread.php?t=287546
The reader I'd purchased was a cable connected model but having recently discovered a possible issue with the car's idle control valve I decided to try to read the codes again and this time I bought a bluetooth OBDII reader, "just in case", and was pleased to find it worked perfectly.
So I was able to read and clear all codes.
I found an old code from months ago P0420 (catalyst / O2 sensor related) which had kept the CEL on, and discovered P0102 too which seems to suggest the issue is with the MAF rather than the IACV.
So if you've tried unsuccessfully to read and clear fault codes on your car I can recommend you try one of these Bluetooth readers. I got mine for £4.09 delivered from the UK in 3 days.
Details as follows
OBD2 ELM327 Car Scanner V2.1 Bluetooth Android Torque Auto Diagnostic Scan Tool
https://www.ebay.co.uk/itm/OBD2-ELM3...72.m2749.l2649
FYI the one that would read but not clear the codes cost £10.95, as below
EOBD OBDII OBD2 Car Fault Code Reader Vehicles Scanner 2 CAN BUS Diagnostic
I've attached a pic of the two readers, you'll find them both on ebay.
HTH someone else