Circuit/System Description

The ignition control (IC) module controls spark timing when the engine is cranking. During this Bypass mode of operation, the IC module triggers each ignition coil in the proper sequence at a pre-calibrated timing advance. The IC module is connected directly to the powertrain control module (PCM) and includes the following circuits:

• The CKP sensor 1 signal circuit
• The CKP sensor 2 signal circuit
• The CMP sensor signal circuit
• A shared CKP/CMP 12-volt reference circuit
• A shared CKP/CMP low reference circuit
• A medium resolution engine speed signal circuit
• A low resolution engine speed signal circuit
• A camshaft position signal circuit
• An IC Module low reference circuit
• An ignition voltage circuit
• A ground circuit

During engine cranking and certain low RPM engine running conditions, the IC module controls the ignition timing at a fixed 10 degree advance. This is called bypass mode. When the PCM receives the 3X low resolution engine speed signal from the IC module, 5 volts is applied to the IC timing signal circuit from the PCM. This signals the IC module to allow the IC timing by the PCM. The PCM sends spark timing signals to the IC module on the IC timing control circuit. The PCM monitors the IC timing signal circuit for errors.