PCM CONTROLLED CHARGING SYSTEM
Description
PCM controlled charging system provides many additional benefits over integral generator regulator system.
First benefit is improved battery life. In an integral generator regulator system, regulator set point is established
by a temperature sensor in the regulator which estimates battery temperature. With PCM controlled generator,
regulator voltage set points are determined by PCM and communicated to regulator via generator
communication line. PCM uses a calibratable algorithm to estimate battery temperature. Improving battery
temperature will reduce battery damage caused by over and undercharging.
Second benefit is improved engine performance. Whenever PCM senses a Wide Open Throttle (WOT), PCM
will momentarily lower regulator voltage set point. This reduces torque load of the generator on engine and
improves acceleration. PCM has a calibratable time limit on this reduced voltage feature. This prevents the
generator output from being cut back for an extended WOT period, which could cause battery discharge.
Third benefit is improved idle stability. In response to PCM generator communication signal, regulator uses a
generator monitor signal to provide feedback to PCM. Generator monitor signal provides PCM with charging
system information. If the charging system receives a transient electrical load which would normally affect idle
stability, the PCM is notified. Because PCM can anticipate additional loads, actions can be taken to minimize
idle sag. PCM can choose to either reduce regulator set point or increase engine idle speed.
Fourth benefit is reduced cranking efforts. PCM can reduce mechanical load on starter by initially commanding
a low voltage set point. This may improve start times.
If PCM detects a charging system error, charge indicator will illuminate. Charge indicator will illuminate if
PCM fails to see a signal on generator monitor line for a time period greater than 500 milliseconds. This
command will also be used to indicate over-voltage conditions detected by generator.
Each time ignition switch is turned to RUN position, cluster will perform a bulb check by illuminating charge
indicator. PCM will send a low voltage command if charging system is functioning properly. This message
should be sent 250-450 milliseconds after ignition switch is turned to RUN position. If a low voltage command
is not received by cluster, cluster will continue to illuminate charge indicator indefinitely.
Generator Communication
PCM controlled charging system provides improved battery life and improved engine performance. PCM
controlled generator regulator voltage set point is determined by PCM and communicated to the regulator by the
Generator Communication (GEN COM) circuit. PCM will use a calibratable algorithm to estimate battery
temperature, reducing damage to battery by overcharging or undercharging. At Wide Open Throttle (WOT),
PCM will momentarily lower the regulator voltage set point, reducing torque load on engine and improving
acceleration. PCM has a calibratable time limit on the reduced voltage feature to prevent decreased generator
output for an extended WOT period, which may cause battery discharge.
Generator Load
Generator Load Input (GLI) circuit is used by PCM to determine generator load on engine. As generator load
2003 Ford Pickup F150
2003 ENGINE PERFORMANCE Theory & Operation - CNG, Flex-Fuel & Gasoline