When I kick down my signum 2.2 auto it goes into safety mode and the trans mission warning light comes on.If I stop,switch off ignition and restart it is fine again.
auto boxes are very complex and a code reader may be your best option and should only be worked on by a specialist but a lot of problems regarding automatics relate to the transmission oil and filter,if this hasn`t been done for a while then it may be worth a go.