PP2000 descriptions can be confusing, my best guess is It means the steering wheel airbag is failing the continuity test, (but freely admit it could just as easily be the drivers seatbelt pretensioner).....
Disconnect whichever one you find easiest to get to and see if the error message changes / you get another one. If it stays the same you have the culprit - plug & unplug it half a dozen times and it will probably clear.
2002 HDi 2.2 Exec Estate, (2008-12) (wonderful)
2003 HDi 2.2 6-speed Exec Estate (2012-19) (also a gem)
2009 Citroen C5 2.0 HDi VTR+ Estate (godawful heap)
2008 BMW E91 330i touring (great fun - murdered by a reversing SUV)
2007 BMW E91 325i touring (slower smoother quieter)
Hi Steve, if the car is a later model then the drivers airbag should say either 'trigger 1' or 'trigger 2' so I'm guessing its the pretensioner too.
If you unplug the connectors, please make sure the key has been out of the ignition for a good 5 minutes first.
2003 2.2hdi estate - mine 1998 Volvo 940 auto estate - also mine 2019 Citroen C3 something - the wife's PP2000 user, can help with faults / diagnostics in the Bournemouth area.