Hi
I have a 1998 v70 2.5 ltr petrol and today the ecu warning light came on, but the car still appears to drive fine.
I service and maintain the car myself, the car has covered 155k miles and has recently had a cambelt, throttle body clean and 5 new ignition coils and is regularly serviced by me.

I have also fitted a LPG conversion to the car, (at 148k miles) and so far this has been fine. (The kit was from www.tinleytech.co.uk) I can switch between LPG and petrol and the light is still on, but performance is fine...

I've a feeling this is a faulty lambda sensor (or two) as this was replaced on my car before I bought it (130k miles). I've no idea how long they last on volvos.

Has anybody else had any similar symptoms on these cars? Or can anyone shed any light?
I thought I'd try the forum before going for a dealership code read diagnosis...

Thanks in advance and great forum.

I solved the problem myself....!! but I thought I'd post it for anyone interested

It turns out that the LPG regulator was at fault. The diaphragm has "settled" in the 7k miles since the LPG system was fitted and as a result the LPG pressure has dropped slightly. The mixture is therefore slightly leaner and the volvo ECU has flagged the problem. I reset the ECU and no light appears when running on petrol.

Solution - adjust the regulator pressure and problem solved.