Charging System

The PCM  -controlled, or Smart Charge charging system determines the optimal voltage setpoint for the charging system and communicates this information to the voltage regulator. The Smart Charge charging system is designed to set 1 of 6 DTCs  any time a charging system fault is present. All of the DTCs  can set continuous faults, but not all DTCs  set as on-demand faults.

This system uses 2 communication lines between the PCM  and the generator/voltage regulator. Both of these communication lines use PWM  . The generator communication (GENCOM) line communicates the desired setpoint from the PCM  to the voltage regulator. The generator monitor (GENMON) line communicates the generator load and error conditions to the PCM  . The GENCOM command is only sent by the PCM  when it is necessary to adjust the voltage setpoint. If the setpoint does not need to be changed, several seconds may elapse between PCM  GENCOM commands. This normal operation appears in the PID  as occasional bursts of pulse-width commands. The third pin on the voltage regulator, the "A" circuit pin, is a circuit dedicated to monitor or sense battery voltage.

The PCM  simultaneously controls and monitors the output of the generator. When the current consumption is high or the battery is discharged, the PCM  raises engine speed as needed to increase generator output. The generator charges the battery and at the same time supplies power for all required electrical loads. The battery is more effectively charged with a higher voltage when the battery is cold and a lower voltage when the battery is warm. The PCM  uses a signal from the IAT sensor to adjust the charging voltage according to the battery temperature. The PCM  also uses other inputs to control the charging system voltage such as the VSS and engine coolant temperature. The voltage setpoint is calculated by the PCM  and communicated to the voltage regulator by the GENCOM circuit based on the needs of the vehicle and the conditions.

The PCM  turns off the generator during cranking to reduce the generator load and improve cranking speed. Once the engine starts, the PCM  slowly increases generator output to the desired voltage.

The PCM  reports any charging system faults and sends a message through the HS-CAN  to the BCM  . The BCM  controls the charging system warning indicator by sending a message over the MS-CAN  to the IPC  . The IPC  then controls charging system warning indication based on the message from the PCM  through the BCM  . The status of the PCM  charging system warning indicator and/or message is confirmed by viewing PCM PID  generator fault indicator lamp (GENFIL). Any charging system fault detected by the PCM  results in 1 or more DTCs  being set and the PID  GENFIL having a status of On. If equipped with a charging system warning indicator, the IPC  turns the indicator on or off. If equipped with a message center, the IPC  displays a CHECK CHARGING SYSTEM message. In some instances, the CHECK CHARGING SYSTEM message may not display if the ignition is ON and the engine is off.

Under certain circumstances, the charging system may have a concern, but still keeps the battery charged and the vehicle running. GENCOM normally initiates charging, but the generator may charge with a fault in this circuit. If the engine operates at more than 2, 000 Revolutions Per Minute (RPM) momentarily, the generator may self-excite or start charging on its own. The charging system warning indicator is illuminated and/or CHECK CHARGING SYSTEM message is displayed, and the generator operates in a default mode (approximately 13.5 volts) until the engine is turned off. When the engine is restarted and the engine operates at more than 2, 000 Revolutions Per Minute (RPM) momentarily, the generator may again self-excite and again the charging system warning indicator is illuminated and/or CHECK CHARGING SYSTEM message is displayed.

The PIDs  and their associated descriptions used in the charging system diagnosis are listed below: