Principles of Operation

PRINCIPLES OF OPERATION

The generator on this vehicle has a built-in voltage regulator set point. The generator determines optimal charging system voltage based on temperature. The generator has a communication line (GEN MON) indicating the generator operating duty cycle (including the generator load and error conditions) to the powertrain control module (PCM). The GEN MON circuit is a pulse width modulated (PWM) signal. The GEN MON communication line is also used for fault indication. If there is an error condition, the PCM sends a signal to the instrument cluster (using the standard corporate protocol [SCP] bus) to turn on the charging system warning indicator. The generator has an I terminal which is used for initially turning on the generator when the engine is started. The generator also has a dedicated battery sense terminal (A terminal), which is used to sense the battery voltage.

This is a System 3 charging system, which uses the GEN MON line to monitor the charging system through the PCM and includes a PCM-controlled I (ignition) circuit to the generator. System 3 charging systems are virtually identical in design and therefore, share the same diagnostics.

Circuit Description

Positive Battery Output (B+) Terminal Circuit 30-BA6 (RD)
Generator output voltage is supplied through the positive battery output (B+) terminal on the rear of the generator to the battery and the electrical system.

A Circuit 30-BA25 (RD)
This is the battery voltage sense or A circuit and is used to sense the battery voltage.

Circuit 8-BA25 (WH/RD)
The GEN MON circuit communicates the generator load and error conditions to the PCM. The PCM sends a signal to the instrument cluster using the SCP bus to turn on the charging system warning indicator if there is an error condition.

Circuit 10-BA25 (GY/RD)

NOTE: If the I circuit 10-BA25 (GY/RD) is open or shorted to ground, the generator does not function. If the engine speed exceeds 3,000 rpm, the generator self-excites, and begins to function normally (the battery light turns off and the generator operates normally) until the engine is turned off. This is a limp-home mode for customer safety.

This is the generator I (ignition) circuit. This circuit is used to turn the generator on when the engine is started. Once the generator is turned on, the generator only turns off when the engine is turned off.