run the fault codes
dark smoke ( black) is an indication of incorrect air/fuel mixture
this can be from leaking injectors, faulty seal , over pressure in fuel system, faulty heated oxygen sensors, blocked air filter, faulty MAF/VAF sensors
the fault codes reading will give a better indication of where to start in the fixing process
More than likely a vacuum leak. The steering is not really locking, that would be your power steeing not working because the engine is quiting. Look for a vacuum leak.
Many sensors can fail on a car. The usual suspect is the crankshaft sensor (or camshaft sensor). Your first course of action should be to get a diagnostic check done to see if any error codes come up.
It could also perhaps be the PEM ( Fuel Pump Electronic Control Module) at fault. I think - I'm not too sure - that some Volvos had trouble with this unit, as water somehow managed to get inside it.
The PEM should be located somewhere close to the fuel tank.
The link below is of generic images:
volvo pem Google Search
If Volvo customer service deny there is a recall it is possibly something that has been misreported or misunderstood or perhaps it doesn't apply to vehicles in your country or region.
If in doubt I suggest you contact a motoring forum or a motoring organisation or any big newspaper or magazine with interests in consumer rights and/or motoring.
The service indicator can be reset as follows: Place the key in position 1, push and hold the trip odometer reset, the trip odometer will zero, turn the key to position 2 while continuing to hold the trip odometer reset. The odometer number will return to the previous value and the service indicator will be reset.
