The engine code C1173 is the main thing to checked is to confirm the operation of the VCT solenoid. You are looking for a sticking or stuck VCt solenoid valve produced by pollution. Raise to car precise repair manual to perform factor tests for the VCT unit. The C1173 engine code is a type of chassis problem. The valves of respective cylinder are closed using a pair of arms that change the straight engine’s roller-type rocker arm. The C1173 code is one of these arms follows the cam profile while the 2nd arm joins to the valves. Through standard engine process the 2 arms are combined by a locking pin.