" P1125 for this engine is Throttle Valve Control Motor. The sub codes (there are 5 in total) 61 and 62 would have told you exactly what the fault was e.g. circuit malfunction, signal improbable etc.
If the car had been diagnosed using either Vauxhall's Tech 2/Midi, Vauxcom, Opcom or Bosch KTS, then a full description of the code and sub codes would have been more accurate.
First step, without the full code description, is to remove the throttle valve assembly completely and give it a really good clean in case it is carbon build up that is stopping it from working properly. Lubricate the spindle with WD40 and try it. If the code and light return then it will need a new unit. "