'03 diesel Vauxhall Zafira 2 litre turbo engine.
When the engine is warm, pulling up at lights and junctions causes it to switch into 'limp home mode'. 'Spanner and Engine' symbol comes on and performance drops to negligible mode.
Raising the engine revs to over 1500 rpm for 7 seconds restores normal performance.
Any suggestions as to problem cause and recommended solutions?