What does it mean?
Inside your engine, a complex ballet of fuel and fire is being performed. At 2,000 rpm, each spark plug fires 1,000 times, or once every 60 milliseconds. Also, every 60 ms, the fuel injectors deliver a pulse of precisely metered fuel, usually somewhere between one and four milliseconds long. Additionally, vehicles equipped with variable valve timing (VVT) need to vary intake and exhaust timing, as well as lift in some cases, depending on engine speed and load.
Obviously, timing is everything and, in the modern engine, timing down to the millisecond is absolutely essential for proper operation, power delivery, and fuel economy. Regarding the most basic timing in an engine, the engine control unit (ECU) monitors the crankshaft position sensor, often abbreviated as CKP.
The CKP sensor reacts to a toothed wheel on the crankshaft, generating a signal, which the ECU used to determine two very important data points – engine speed (RPM) and engine position, or cylinder #1 top dead center (TDC). Using this information, the ECU modulates all other engine functions.