Has any one had a problem with the engine electrical sign keep showing?

i have a Astra Ls 2003 model and have taken to a garge to be checked and pluged into the machine to check all systems and it came back with no problems but a in put voltage of 32volts but i still keep getting the spanner and car symbol showing on the dash board after driving the car 200 yds up the road after first startingthe car in the morning if i pull in swicth the engine off and restart it the light goes out does any one else have the same problem and if so how was it solved