Renault Megane check injection and service light flashes for a few seconds

HAVE REPLACED THIS ENGINE WITH ANOTHER GOOD ONE. THEN CHECK INJECTION LIGHT AND SERVICE LIGHT CAME ON AND STAYED ON PERMANENT. DIAGNOSTICS MAN SUGGESTED TO CHANGE GLOW PLUGS. WHICH I DID AND BOTH LIGHTS WENT OUT AND STAYED OFF UNTIL I DROVE THE CAR FOR ABOUT A MILE. AT TRAFFIC LIGHTS, THE CHECK INJECTION LIGHT COMES ON FOR APPROX 2-3 SECONDS FOLLOWED BY SERVICE LIGHT FOR ONE SECOND OR LESS. THESE LIGHTS STAY OFF WHILST THE CAR IS IN MOTION BUT START TO FLASH WHEN I COME TO A HALT AT TRAFFI LIGHTS. ALSO, I HAVE NOTICED THAT OUTSIDE AIR TEMPERATURE DOES NOT SHOW UNTIL AFTER A FEW MINS OF ENGINE BEING STARTED. I HAVE NOTICED THERE IS A PIPE MISSING OR NOT CONNECTED TO A (SORT OF) CANISTER NEAR EGR VALVE OR A BAD CONNECTION. EGR VALVE IS CHANGED. WILL APPRECIATE ANY HELP. THANKS IN ANTICIPATION.