PCM manages idle rpm on per-cylinder basis based on angular velocity of IP shaft, measured in the Optic Sensor system - any increase in velocity gets reduced fuel, any decrease gets increased fuel - that's how idle rpm is maintained as crank loading increases\decreases, such as engaging any gear from PARK\NEUTRAL, or turning on AC, or lites, etc - a Cyl Imbalance DTC indicates that Cyl did not respond - if the same DTC repeats regularly, would indicate a bad injector, leaky valve(s), leaky rings, etc in that cylinder - not too important if occurs occasionally at cold-start, tho worth keeping an eye on it if it's always the same cylinder, or with increasing frequency of occurance.
