toro Sprinkler system stuck in zone 2

I have a 3 zone sprinkler system that sticks in zone 2. My zone 1 and zone 3 both turn off when the timer runs to 0 minutes. I have to turn off my entire system to get zone 2 to stop sprinkling. I can find only one control valve in a round housing in my yard. Should I have 3 of these control valves in my yard, one valve for each zone? If I do have only control valve for all 3 zones, should I replace the diaphragm in the 1 control valve housing that I have been able to find in my yard?

I think there must be two other zone valves somewhere. But you say the zone 2 goes off when you turn off the entire system: you mean electrically, or do you shut off the water supply valve to the sprinkler system when you turn off the entire system. If turning off the water and then turning it on again shuts off zone 2, I think zone 2's valve wherever it is, is sticking. I am not a sprinkler expert, but have lots of experience on them. I never heard of a 3 zone valve built into one unit. On the one valve you did find, how many wires attach to it? If only 2, then that valve is only for one zone

You definitely have two more valves somewhere. when you find the one for zone two try turning the flow control knob in the center of the valve clockwise 1 or 2 turns and that should let the valve close on it's own. But if the zone comes back on when you turn the water back on then you need to change out the diaphram in the valve.