OK, wokwi.com makes it easy, the code my hack functions correctly for the signal as you have said it will appear.
I see with my simulation that if the ecusignal changes during the 2 second relay pulse, the program will:
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eventually see the ecusignal change and after the 500 ms degltiching period
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execute the change in state and pulse the other relay.
So you have to press the pushbutton and hold it to see one relay pulse, then release it to see the other.
Typically how long between changes in the ecusignal you digitalRead on S1?
How should the program respond to changes in under 2.5 seconds?
What is an ecu? 
a7