I replaced my radiator and then the car won't start?

I disconnected the Neg Battery cable, prior to working on it. After I replaced the radiator, I was unable to start the car.

It turns over no prob, but the check engine light Does Not come on. I changed out the Main Relay under the dash and made sure the fan were reconnected and one was not, so I reconnected it. All the fuses are good.

I do not hear the fuel pump kicking on nor do I hear a click from any relays under the hood.

I do hear a click under the dash by the radio and the Green "S" light flashes with the click, when the key is turned to start the car.

Any suggestion? Thanks

 

Most likely the ECU ground located on the thermostat housing is not attached or loose.

 

Wow! It worked! Yes, I forgot to reattach the ground to the thermostat housing! Thank you!!!!

sigh of relief!!!!