Injection Timing

All engines use a sequential port fuel injection system. This means that the injectors have a specific firing order and fuel injection is timed to piston movement. The spark plugs and injectors are fired in the same order: 1-5-3-6-2-4.

In order for the PCM to fire the injectors in a specific order timed to crankshaft and piston movement, it has to establish a reference point. Establishing the reference point requires PCM inputs from the Crankshaft Position (CKP) sensor and Camshaft Position (CMP) sensor. PCM will not allow engine to operate if CKP sensor signal is not received.

Crankshaft Position (CKP) sensor is located on transmission bell-housing, and provides PCM with crankshaft angle and speed. The PCM converts crankshaft speed into engine RPM and crankshaft angle into piston position.

The slotted flywheel/flexplate, rotating past CKP sensor, contains 3 groups of 4 slots located 120 degrees apart. Each group of slots represents the position of 2 of the pistons. Pistons No. 1 and 6 approach TDC at the same time and use the same flywheel slot. Pistons No. 2 and 5 are matched, while piston No. 3 is matched with piston No. 4.