Calculating Speark Advance

The PCM uses information from the MAP and Engine Coolant Temperature (ECT) sensors in addition to the RPM in order to calculate the spark advance as follows:
^ A low MAP output voltage = More spark advance.
^ A cold engine = More spark advance.
^ A high MAP output voltage = Less spark advance.
^ A hot engine = Less spark advance.

Therefore, a low MAP output or a high resistance in the coolant sensor circuit could cause the detonation. A high MAP output or a low resistance in the coolant sensor circuit could cause poor performance.