Electronic Ignition Timing Control

Ignition timing is calculated by PCM based on current engine status. PCM provides 3 modes of ignition timing control. Each ignition timing mode provides the most suitable spark advance for optimal engine performance. The 3 modes are as follows:

• Initial Timing Control (At Engine Start)
  
  Initial Timing Control ignition advance provides better starting performance during start-up when engine speed is less than 500 RPM. PCM sets initial ignition timing advance to 5 degrees BTDC.
• Basic Timing Control (After Engine Start)
  
  After engine is running, ignition timing advance is determined by combining Basic Timing Control and Compensating Timing Control. Basic Timing Control ignition advance is based on engine coolant temperature, engine speed and intake air volume. Ignition timing advance value calculated from ECT sensor, CMP sensor and MAF sensor input is added to the 5 degrees BTDC initial advance and then modified by the Compensating Timing Control value.
• Compensating Timing Control
  
  Compensating Timing Control is added to Basic Timing Control value and varies according to engine and vehicle conditions. Conditions utilized for determining Compensating Timing Control value, are engine coolant temperature, intake air temperature and engine idling demands.

PCM cannot operate ignition system without engine speed signal from camshaft position sensor. PCM controls ignition timing by controlling ignition coils. Ignition timing is controlled by PCM and is adjustable. See IGNITION TIMING in appropriate ON-VEHICLE ADJUSTMENTS article.