Charging System: Overview Ford Escape II

Principles of Operation

The PCM-controlled charging system, or "Smart Charge" charging system, determines the optimal voltage set point 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 will set as on-demand faults.

DTC CHART

This system uses 2 communication lines between the PCM and the generator/voltage regulator. Both of these communication lines use Pulse-Width Modulation (PWM). The generator communication (GENCOM) line communicates the desired set point 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 set point. If the set point does not need to be changed, several seconds may elapse between PCM GENCOM commands. This normal operation will appear 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 will raise engine speed as needed to increase generator output. The generator charges the battery and at the same time supplies power for all of the electrical loads that are required. 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 is able to adjust the charging voltage according to the battery temperature by using a signal from the Intake Air Temperature (IAT) sensor. The PCM also uses other inputs to control charging system voltage such as the Vehicle Speed Sensor (VSS) and Engine Coolant Temperature (ECT). This means the voltage set point 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 desired voltage.

The PCM controls the charging system warning indicator by sending a message over the High Speed Controller Area Network (HS-CAN) to the Instrument Cluster (IC) module. The IC module will then control charging system warning indication based on the message from the PCM. The status of the PCM charging system warning indicator and/or message can be confirmed by viewing PCM PID generator fault indicator lamp (GENFIL). Any charging system fault detected by the PCM will result 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 IC module will turn the indicator ON or OFF. If equipped with a message center, the IC module will display a CHECK CHARGING SYSTEM message. When the ignition is ON and the engine is OFF on vehicles equipped with a message center, the CHECK CHARGING SYSTEM message may not be displayed. For information regarding the IC module and message center, refer to INSTRUMENTATION, MESSAGE CENTER, AND WARNING CHIMES .

Under certain circumstances, the charging system may have a concern, but still keep the battery charged and the vehicle running. GENCOM is normally used to initiate charging, but the generator may charge with a fault in this circuit. If the engine is operated at greater than 2,000 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 is operated at greater than 2,000 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

PID CHART

Normal Operation

With the engine running, the charging system supplies voltage to the battery and the vehicle electrical system through the battery B+ cable. The voltage that is supplied to the vehicle electrical system is used for the operation of the various vehicle systems and modules. Many modules monitor this voltage and if it rises above a calibrated set point, a DTC will be set.

1. DTC P0563 (System Voltage High) - If the module detects a voltage from the charging system higher than 15.2 volts this DTC will be set. This DTC will not be set in the PCM unless the vehicle speed is above 8 km/h (5 mph).

This pinpoint test is intended to diagnose the following

1. Fuse
2. Wiring, terminals or connectors
3. Engine, generator and battery grounds
4. Battery
5. Generator
6. PCM

With the engine running, the charging system supplies voltage to the battery and the vehicle electrical system through the battery B+ cable. The PCM monitors this voltage through the battery positive post through the Battery Junction Box (BJB). If this voltage drops 1.5 volts or more below the generator voltage desired, this DTC will be set after 30 seconds.

This pinpoint test is intended to diagnose the following

1. Fusible link
2. Wiring, terminals or connectors
3. Battery
4. Generator
5. PCM

The PCM monitors the generator output via the generator monitor (GENMON) circuit. The PCM uses the generator communication (GENCOM) circuit to command the generator to either increase or decrease output. If the GENCOM circuit (generator control circuit) or the A sense circuit are open or shorted to ground, the PCM will be unable to control the generators output. When the engine rises above approximately 2,000 RPM, the generator will default to a steady voltage of approximately 13.5 volts and the PCM will send a request to the Instrument Cluster (IC) to illuminate the charging system warning indicator lamp.

1. DTC P0620 (Generator Control Circuit) - If the GENCOM circuit or A sense circuit are open or shorted to ground, the PCM will set this DTC.

This pinpoint test is intended to diagnose the following

1. Fuse
2. Wiring, terminals or connectors
3. Generator
4. PCM

The PCM monitors the generator output via the GENMON circuit (generator field terminal circuit). If the PCM cannot read the GENMON circuit due to an open or short to ground, when the engine rises above approximately 2,000 RPM, the generator will default to a steady voltage of approximately 13.5 volts and the PCM will send a request to the Instrument Cluster (IC) to illuminate the charging system warning indicator lamp. A GENMON duty cycle of 3% or less indicates a short to ground fault is present and will result in DTC P0625 setting in the PCM. A GENMON duty cycle of 98% or more indicates an open or short to voltage fault is present and will result in DTC P0626 setting in the PCM.

1. DTC P0625 (Generator Field Terminal Circuit Low) - If the GENMON circuit is shorted to ground, the A sense circuit is open or the B+ circuit is open, the PCM will set this DTC. This DTC can also be set by a faulty PCM or generator.
2. DTC P0626 (Generator Field Terminal Circuit High) - If the GENMON circuit is open or shorted to power, the PCM will set this DTC. This DTC can also be set by a faulty PCM or generator.

This pinpoint test is intended to diagnose the following

1. Fuse
2. Wiring, terminals or connectors
3. Engine, generator and battery grounds
4. Battery
5. Generator
6. PCM

The PCM monitors the generator output via the generator monitor (GENMON) circuit. The signal that is monitored by the PCM on the GENMON circuit is a controlled frequency range. If the signal is outside of this prescribed range, the PCM will be unable to read the signal. When the engine rises above approximately 2,000 RPM, the generator will default to a steady voltage of approximately 13.5 volts and the PCM will send a request to the Instrument Cluster (IC) to illuminate the charging system warning indicator lamp.

1. DTC P065B (Generator Control Circuit Range/Performance) - If the input frequency was continuously less than 80 Hz or more than 200 Hz the PCM will set this DTC. Additionally, if the signal shows a faulted condition that is happening in a fluctuating manner, the PCM will track the fluctuations between faulted and normal conditions. If the fluctuations occur frequently within a short amount of time, this DTC will also be set.

This pinpoint test is intended to diagnose the following

1. Wiring, terminals or connectors
2. Generator
3. PCM

The generator is belt-driven by the engine accessory drive system. There are many sources of generator noise: bearing noise, electrical fault noise and/or generator pulley misalignment. A generator with certain types of diode or stator failures may also produce an audible noise.

This pinpoint test is intended to diagnose the following

1. Accessory drive belt
2. Loose bolts/brackets
3. Generator/pulley

The generator radio suppression equipment reduces interference transmitted through the speakers by the vehicle electrical system.

This pinpoint test is intended to diagnose the following

1. Generator
2. Wiring, terminals or connectors
3. In-vehicle entertainment system