2003 Chevy S-10

I have a 2003 S10 Extreme 4.3, The truck recently was flooded. Despite what people have said just to leave it at a total loss I have just been slowly playing around with the truck to get it back to pre flood condition. I have taken all the steps to remove the water from the engine, transmission, differential, cab, dash, etc. I have come to the point to try and start the truck and when attempting to start the starter just makes a clicking sound. All the gauges seem to work fine. However the service engine soon light stays on while the ignition is in the on position. Does this indicate a ecu problem?