Compression Sense Ignition (CSI)

The Electronic Ignition (EI) module supplies a signal to the PCM based on which cylinder has just fired on its compression stroke. Because of the opposite polarity, the simultaneous fire of #1/#4 or #2/#3 cylinders are of opposite polarity as well. Under most conditions (except low MAP), the waste spark cylinder fires before the compression cylinder in sequence. The EI module can determine which cylinder has fired by the polarity sequence along with the Ignition Control (IC) inputs. The EI module can base the cam out signal on either 1/4 or 2/3 cylinder events. The cam out signal along with the double pulse of the 7X reference signal synchronizes spark and fuel timing.

The cam out signal is used too correlate crankshaft to camshaft position so that the PCM can determine which cylinder is ready to get fueled by the injector. The signal is also used to determine which cylinder is misfiring when misfire is present. If the PCM receives and intermittent signal from the EI module, then the CMP resync counter will increment. When the PCM will fuel the engine using the Alternating Synchronous Double Fire (ASDF) method.

A malfunction in the compression sense circuits will cause a DTC P0340 or P0341.