The CMPS(Camshaft Position sensor) detects the position of the camshaft. The CMPS identifies when piston number 1 is on its compression stroke. A signal is then sent to the ECM and used for synchronizing the sequential firing of the fuel injectors. Coil on plug ignition applications use the CMPS signal to select the correct ignition coil to fire. Inline engines with 2 camshafts and with CVVT(Continuously Variable Valve Timing) are equipped with 2 CMPSs. The second sensor identifies the exhaust camshaft position.