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Home >> Buick >> 2007 >> Allure CX >> Repair and Diagnosis >> External Pages >> Different car >> Section 21 (Engine Control System & Fuel System - 3.8L - Introduction (2 Of 2)) >> Description and Operation >> Electronic Ignition (EI) System Description >> Modes of Operation

Modes of Operation

WARNING: This page is about a different car, the 2008 Buick LaCrosse and 2008 Buick Allure. However, it is still accessible from the selected car via links, so may be relevant.

The PCM has 2 modes of operation:

Bypass mode is used by the ICM to control the triggering of each coil for base spark timing. During bypass mode the timing is fixed at 10° BTDC and the PCM does not apply 5 volts to the IC timing signal circuit. The Bypass mode is used during each of the following conditions:

IC Mode is used by the PCM to accurately control spark timing for all driving conditions. During IC mode the PCM is receiving the 18X and the 3X reference pulses from the ICM and is supplying 5 volts to the IC timing signal circuit. This allows the PCM to control spark timing. Knock Sensor (KS)

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