Charging System - General Information: Overview Mercury Sable V

Principles of Operation

This vehicle is equipped with a PCM-controlled charging system, which determines the optimal voltage setpoint for the charging system and communicates this information to the voltage regulator. This system is unique in that it has 2 unidirectional communication lines between the PCM and the generator/regulator. Both of these communication lines are pulse-width modulated (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 third pin on the voltage regulator, the A circuit pin, is a dedicated battery voltage sense line.

The PCM uses a calibratable algorithm to estimate battery temperature and to reduce battery damage caused by over and under charging. Using this algorithm, the PCM determines the optimal voltage setpoint for the charging system and communicates this information to the voltage regulator on the GENCOM circuit. While this is occurring, the PCM is also monitoring the GENMON circuit for charging system information, such as transient electrical loads or errors.

If the PCM senses when the charging system receives a transient electrical load (which may cause poor idle quality, such as an idle roll) the PCM can then adjust the injectors opening time to account for the transient electrical load. In this manner, the PCM can maintain a consistent idle speed.

If the PCM detects a charging system error, it broadcasts a CHARGING SYSTEM STATE STATUS message through the controller area network (CAN) communication link, causing the instrument cluster (IC) to illuminate the charging system warning indicator. The charging system warning indicator is illuminated if the PCM fails to see a signal on the GENMON circuit for a time period greater than 500 ms. This telltale is used to indicate over-voltage conditions detected by the PCM.

The PCM also reduces the mechanical load on the starter by initially commanding a low voltage setpoint (using the GENCOM circuit) in order to improve start times and reduce load on the starter and its related system.

Each time the key is cycled to the ON position, the IC initiates a bulb check by illuminating the charging system warning indicator. This operation is called prove-out. The PCM then issues a CHARGING SYSTEM STATE STATUS - OK message if the charging system is functioning correctly. This message is sent once the engine is running and the charging system is determined to be operating correctly. If the cluster does not receive an OK message, the cluster lights the charging system warning indicator indefinitely. Vehicles equipped with a message center display CHECK CHARGING SYSTEM any time a charging system error is present.

This is a System 4 charging system, which uses the GENMON and GENCOM lines to control and monitor the charging system through the PCM. System 4 charging systems are virtually identical in design and therefore, share the same diagnostics. The circuit numbers and colors may be different, but the functions are the same. System 4 charging systems may use any type of generator, as the generator type usually depends on the engine packaging and/or output requirements versus cost.

Normal Operation

The generator output voltage is supplied through the positive battery output (B+), circuit SDC02 (RD) terminal on the rear of the generator to the battery and electrical system. During normal operation the charging system warning indicator is off with the key in the ON position and the engine running. The charging system warning indicator is on with the key in the ON position and the engine off.

This pinpoint test is intended to diagnose the following

1. High key-off current drain(s)
2. Engine, generator and battery grounds
3. Positive battery cable
4. Wiring, terminals or connectors
5. Battery
6. Generator

Scheme 1

Scheme 2

1. A1 CHECK THE BATTERY CONDITION Carry out the Battery - Condition Test to determine if the battery can hold a charge and is OK for use. Refer to «BATTERY, MOUNTING AND CABLES»(ref-293478) article. Does the battery pass the condition test? YES : Go to A2 . NO : INSTALL a new battery. REFER to «BATTERY, MOUNTING AND CABLES»(ref-293478) article. TEST the system for normal operation.
2. A2 CHECK THE GENERATOR OUTPUT Carry out the Generator On-Vehicle Load Test and No Load Test. Refer to the Component Tests in this article. Does the generator pass the component tests? YES : Go to A3 . NO : Go to «Pinpoint Test B»(ref-293457-S37259407352008080700000) .
3. A3 CHECK FOR CURRENT DRAINS Carry out the Battery - Drain Testing. Refer to the Component Tests in this article. Are any circuits causing excessive current drains? YES : REPAIR as necessary. TEST the system for normal operation. NO : Go to A4 .
4. A4 CHECK THE VEHICLE GROUNDS Key in START position. Turn on accessory loads, such as high blower and high-beam headlamps. With the engine running, measure the voltage drop between the generator housing and the negative battery terminal. Is the voltage drop less than 0.1 volt? YES : Go to A5 . NO : CHECK the engine ground, generator ground and the battery ground for corrosion. TEST the system for normal operation.
5. A5 CHECK THE VOLTAGE DROP IN THE B+ CIRCUIT SDC02 (RD) With the engine running and accessory loads ON, measure the voltage drop between generator B+ C102b, circuit SDC02 (RD) and the positive battery terminal. Is the voltage drop less than 0.5 volt? YES : CHECK if the customer left any electrical system(s) on or if there is an intermittent excessive battery draw. TEST the system for normal operation. NO : CHECK for any corrosion in the B+ SDC02 (RD), positive battery cable and/or connections. REPAIR as necessary. TEST the system for normal operation.

With the engine running, the charging system warning indicator is off. The A circuit SBB17 (RD) from the battery B+ to the generator regulator is 13-15 volts. This voltage feedback is used by the regulator to maintain the battery voltage at the desired setpoint. The S (stator) circuit (internal to the generator) is used to monitor generator operation. This circuit and other regulator internal conditions are checked by the regulator to allow the PCM to turn off the charging system warning indicator by sending a message over the controller area network (CAN) bus to the instrument cluster (IC). The positive battery output (B+) circuit SDC02 (RD) is the generator output voltage supplied to the battery and electrical system.

This pinpoint test is intended to diagnose the following

1. Generator
2. PCM

With the engine running, the charging system warning indicator is off. The A circuit SBB17 (RD) from the battery B+ to the generator regulator is 13-15 volts. This voltage feedback is used by the regulator to maintain the battery voltage at the desired setpoint. The S (stator) circuit (internal to the generator) is used to monitor generator operation. This circuit and other regulator internal conditions are checked by the regulator to allow the PCM to turn off the charging system warning indicator by sending a message over the controller area network (CAN) bus to the instrument cluster (IC). The positive battery output (B+) circuit SDC02 (RD) is the generator output supplied to the battery and electrical system.

This pinpoint test is intended to diagnose the following

1. Generator
2. Circuitry
3. IC
4. PCM

The generator is belt-driven by the engine accessory drive system.

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. Circuitry
3. In-vehicle entertainment system

Various control modules within the vehicle operate at a voltage between 10-17 volts. Voltage to these modules is supplied through the vehicle harness to the module(s). Ground for the modules is provided by the modules ground circuit(s). If voltages to these modules rise above 17 volts, DTC B1317 or B1676 may set, or if voltage drops below 10 volts, DTC B1318 or B1676 may set.

This pinpoint test is intended to diagnose the following

1. Battery
2. Charging system
3. Module voltage supply
4. Module ground

Note. DTC B1317 or B1318 can be set if the vehicle has had a discharged battery, has been recently jump started or has had the vehicle battery charged.