Generator charge system failure - 2000 Jaguar S-Type

Do you have a issue with starting the vehicle, slow crank? showing signs of a weak battery, driving at night with headlamps on, are they dim? Does the vehicle die after driving awhile because of no charging- discharged battery? Any messages on the DIC - driver info. center (service charging system) Check engine light illuminated. The charging system on that vehicle are not like charging systems of old, its computer controlled. It has different modes of operation. You may think you have an issue - but don't.

You see the voltmeter in the instrument cluster go below 13 - 14 volts or maybe lower . This computer-controlled system can charge as low as 11 volts or as high as 15 volts depending on the mode. This system will set DTC'S diagnostic trouble codes if it has a problem.

Charging System Description and Operation
Electrical Power Management (EPM) Overview
The EPM system is designed to monitor and control the charging system and send diagnostic messages to alert the driver of possible problems with the battery and generator. This EPM system primarily utilizes existing on-board computer capability to maximize the effectiveness of the generator, to manage the load, improve battery state-of-charge (SOC) and life, and minimize the system's impact on fuel economy. The EPM system performs three functions:
• It monitors the battery voltage and estimates the battery condition.
• It takes corrective actions by adjusting the regulated voltage.
• It performs diagnostics and driver notification.
The battery's condition is estimated during key-off and during key-on. During key-off the SOC of the battery is determined by measuring the open-circuit voltage. The SOC is a function of the acid concentration and the internal resistance of the battery, and is estimated by reading the battery open circuit voltage when the battery has been at rest for several hours.
The SOC can be used as a diagnostic tool to tell the customer or the dealer the condition of the battery. Throughout key-on the algorithm continuously estimates SOC based on adjusted net amp hours, battery capacity, initial SOC, and temperature.
While running, the battery's degree of discharge is primarily determined by a battery current sensor, which is integrated to obtain net amp hours.
In addition, the EPM function is designed to perform regulated voltage control (RVC) to improve battery SOC, battery life, and fuel economy. This is accomplished by using knowledge of the battery's SOC and temperature to set the charging voltage to an optimum battery voltage level for recharging without detriment to battery life.
The Charging System Description and Operation is divided into 3 sections. The first section describes the charging system components and their integration into the EPM. The second section describes charging system operation. The third section describes the instrument panel cluster operation of the charge indicator, driver information center messages and voltmeter operation.


Generator
The generator is a serviceable component. If there is a diagnosed failure of the generator it must be replaced as an assembly. The engine drive belt drives the generator. When the rotor is spun it induces an alternating current (AC) into the stator windings. The AC voltage is then sent through a series of diodes for rectification. The rectified voltage has been converted into a direct current (DC) for use by the vehicles electrical system to maintain electrical loads and the battery charge. The voltage regulator integral to the generator controls the output of the generator. It is not serviceable. The voltage regulator controls the amount of current provided to the rotor. If the generator has field control circuit failure, the generator defaults to an output voltage of 13.8 volts.
Body Control Module (BCM)
The BCM communicates with serial data with the engine control module (ECM) / powertrain control module (PCM) and the instrument panel cluster for EPM operation. The BCM determines the output of the generator and sends the information to the ECM/PCM for control of the generator field control circuit. It monitors the generator field duty cycle signal circuit information sent from the ECM/PCM for control of the generator. It monitors a battery current sensor, the battery positive voltage circuit, and estimated battery temperature to determine battery SOC. The BCM performs idle boost and load management operations.
Battery Current Sensor
The battery current sensor is a serviceable component that is connected to the negative battery cable at the battery. The battery current sensor is a 3 wire hall effect current sensor. The battery current sensor monitors the battery current. It directly inputs to the BCM. It creates a 10 volt PWM signal of 128 Hz with a duty cycle of 0-100%. Normal duty cycle is between 5-95%. Between 0-5% and 95-100% are for diagnostic purposes.

Engine Control Module (ECM) / Powertrain Control Module (PCM)
The ECM/PCM directly controls the generator field control circuit input to the generator. It monitors the generators generator field duty cycle signal circuit and sends the information to the BCM. The ECM/PCM will over ride the BCM control of the generator when one of the following conditions are met:
• The engine cooling fans are on high speed.
• There is a high fuel demand.
• The calculated ambient air temperature is less that 0°C (32°F).
Instrument Panel Cluster (IPC)
The IPC provides a means of customer notification in case of a charging system concern.There is two means of notification, a charge indicator and a driver information center message of SERVICE CHARGING SYSTEM and CHARGING SYSTEM/GENERATOR FAULT.

Charging System Operation
The purpose of the charging system is to maintain the battery charge and vehicle loads. There are 6 modes of operation and they include:
• Charge Mode
• Fuel Economy Mode
• Voltage Reduction Mode
• Start Up Mode
• Windshield Deice Mode
• Battery Sulfation Mode
The ECM/PCM controls the generator through the generator field control circuit. It monitors the generator performance through the generator field duty cycle signal circuit. The signal is a 5 volt PWM signal of 128 Hz with a duty cycle of 0-100%. Normal duty cycle is between 5-95%. Between 0-5% and 95-100% are for diagnostic purposes. The following table shows the commanded duty cycle and output voltage of the generator:


Watch this video. Computer Charging Systems - GM - YouTube

Question edited for clarity, full 'year make model'.
Question moved to the correct category.

Jeff has the answer Up there ^^ and now here.

• Jeff Armer
• Apr 21, 2022
• You need to hook up a professional grade scan tool to check codes in all the computers (modules) in the vehicle . That vehicle has a smart charging system , amp sensor around the battery negative cable. lets the computers know how much current is being used so it knows how much to put back , suppose to help battery last longer . Look that up on the internet ,watch youtube videos .
  https://www.youtube.com/watch?v=xN7SIHgA...
  https://ricksfreeautorepairadvice.com/gm...
• 
  Jeff Armer
• Apr 21, 2022
  SERVICE BATTERY CHARGING SYSTEM
  The BCM and the ECM will send a GMLAN message to the DIC for the SERVICE BATTERY CHARGING SYSTEM message to be displayed. It is commanded ON when a charging system DTC is a current DTC. The message is turned OFF when the conditions for clearing the DTC have been met.
  
  
  DTC - diagnostic trouble codes
  
  Generator
  The generator is a serviceable component. If there is a diagnosed failure of the generator it must be replaced as an assembly. The engine drive belt drives the generator. When the rotor is spun it induces an alternating current (AC) into the stator windings. The AC voltage is then sent through a series of diodes for rectification. The rectified voltage has been converted into a direct current (DC) for use by the vehicles electrical system to maintain electrical loads and the battery charge. The voltage regulator integral to the generator controls the output of the generator. It is not serviceable. The voltage regulator controls the amount of current provided to the rotor. If the generator has field control circuit failure, the generator defaults to an output voltage of 13.8 volts.
  
  Body Control Module (BCM)
  The body control module (BCM) is a GLAN device. It communicates with the engine control module (ECM) and the instrument panel cluster (IPC) for electrical power management (EPM) operation. The BCM determines the output of the generator and sends the information to the ECM for control of the generator turn on signal circuit. It monitors the generator field duty cycle signal circuit information sent from the ECM for control of the generator. It monitors a battery current sensor, the battery positive voltage circuit, and estimated battery temperature to determine battery state of charge (SOC). The BCM performs idle boost.
  
  Battery Current Sensor
  The battery current sensor is a serviceable component that is connected to the battery cable at the battery. The battery current sensor is a 3-wire hall effect current sensor. The battery current sensor monitors the battery current. It directly inputs to the BCM. It creates a 5-volt pulse width modulation (PWM) signal of 128 Hz with a duty cycle of 0-100 percent. Normal duty cycle is between 5-95 percent. Between 0-5 percent and 95-100 percent are for diagnostic purposes.
  
  Engine Control Module (ECM)
  When the engine is running, the generator signal is sent to the generator from the ECM, turning on the regulator. The generator's voltage regulator controls current to the rotor, thereby controlling the output voltage. The rotor current is proportional to the electrical pulse width supplied by the regulator. When the engine is started, the regulator senses generator rotation by detecting AC voltage at the stator through an internal wire. Once the engine is running, the regulator varies the field current by controlling the pulse width. This regulates the generator output voltage for proper battery charging and electrical system operation. The generator field duty terminal is connected internally to the voltage regulator and externally to the ECM. When the voltage regulator detects a charging system problem, it grounds this circuit to signal the ECM that a problem exists. The ECM monitors the generator field duty cycle signal circuit, and receives control decisions based on information from the BCM.
  
  DTC B1516 08 : Battery Current Sensor Signal Invalid
  
  DTC B1516 66 : Battery Current Sensor Wrong Mounting Position
  
  Circuit/System Description
  The battery current sensor is a 3-wire hall effect current sensor. The battery current sensor monitors the battery current. It directly inputs to the body control module (BCM). It creates a 5-volt pulse width modulation (PWM) signal of 128 Hz with a duty cycle of 0-100 percent. Normal duty cycle is between 5-95 percent. Between 0-5 percent and 95-100 percent are for diagnostic purposes.
  
  DTC B1517 Battery Voltage
  
  The body control module (BCM) has designated circuits for monitoring vehicle system voltage. The BCM monitors the system voltage to ensure that the voltage stays within the proper range. Damage to components, and incorrect data may occur when the voltage is out of range. The BCM monitors the system voltage over an extended length of time. If the BCM detects the system voltage is outside an expected range for the calibrated length of time, or the BCM battery sense circuits differ by 2 volts DTC B1517 will set. Other modules also monitor system voltage the system voltage message is sent to the other modules and will default to 12.9 volts.
  

Which module ?

B1318 Battery Voltage Low Audio Control Module REFER to Section 414-00 . B1318 Battery Voltage Low DSM REFER to Section 414-00 . B1318 Battery Voltage Low DVD Player REFER to Section 414-00 . B1318 Battery Voltage Low Instrument Cluster REFER to Section 414-00 . B1318 Battery Voltage Low RCM REFER to Section 414-00 . B1318 Battery Voltage Low Satellite Radio Receiver REFER to Section 414-00 . B1318 Battery Voltage Low SJB REFER to Section 414-00 .
According to this charging system isn't working correctly ! This is a computer controlled charging system .
Principles of Operation
The powertrain control module (PCM) controlled charging system 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 (GEN COM) line communicates the desired setpoint from the PCM to the voltage regulator. The generator monitor (GEN MON) 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 charging system voltage is controlled by the PCM. 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. This means the voltage setpoint is calculated by the PCM and communicated to the regulator by a communication link.
The PCM simultaneously controls and monitors the output of the generator. When the current consumption is high or the battery is discharged (the PCM recognizes this and increases the output of the generator to accommodate), the system is also able to increase the idle speed to increase the charge.
To minimize the engine drag when starting the engine, the PCM does not allow the generator to produce any output until the engine has started. The PCM then progressively increases the output of the generator.
The PCM turns the charging system warning indicator off after the engine is started and illuminates it under fault conditions (when the generator is not generating the correct amount of current with the engine running). The charging system warning indicator is also illuminated by the PCM whenever the key is ON with the engine OFF.
This is a System 4 charging system, which uses the GEN MON and GEN COM 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.

Running the car will drain the battery it if it's not charging ! An if your charging light is on it isn't charging ! Did you check power an grounds on the alternator ? There is a single heavier wire on the back of the alternator, this should have battery voltage ! You may want to take this to a ASE certified repair shop !
Functionality
With the ignition switch in the RUN position, voltage is applied through the warning indicator I circuit 904 (LG/RD) to the voltage regulator. This turns the regulator on, allowing current to flow from battery sense A circuit 35 (OG/LB) to the generator field coil. When the engine is started, the generator begins to generate alternating current (AC) which is internally converted to direct current (DC). This current is then supplied to the vehicle's electrical system through the output (B+) terminal of the generator.
Once the generator begins generating current, a voltage signal is taken from the generator stator and fed back to the regulator S circuit 4 (WH/BK). This voltage feedback signal (typically half the battery voltage) is used to turn off the warning indicator.
With the system functioning normally, the generator output current is determined by the voltage of the A circuit 35 (OG/LB). The A circuit 35 (OG/LB) voltage is compared to a set voltage internal to the regulator, and the regulator controls the generator field current to maintain the correct generator output.
The set voltage will vary with temperature and is typically higher in cold temperatures and lower in warm temperatures. This allows for better battery recharge in the winter and reduces the chance of overcharging in the summer.
Battery Positive Output (B+) Circuit 38 (BK/OG)
The generator output is supplied through the battery positive output (B+) terminal on the back of the generator to the battery and electrical system.
I Circuit 904 (LG/RD)
The I (ignition) circuit 904 (LG/RD) is used to turn on the voltage regulator. This circuit is powered up with the ignition switch in the RUN position. This circuit is also used to turn the charging system warning indicator on if there is a fault in the charging system operation.
A Circuit 35 (OG/LB)
The A (battery sense) circuit 35 (OG/LB) is used to sense battery voltage. This voltage is used by the regulator to determine generator output. This circuit is used to supply current to the generator field (rotor). The amount of current supplied to the rotor will determine generator output.
S Circuit 4 (WH/BK)
The S (stator) circuit 4 (WH/BK) is used to feed back a voltage signal from the generator to the regulator. This voltage is used by the regulator to turn off the charging system warning indicator. The S circuit is fed back externally on external mounted regulator generators.
Visual Inspection Chart Mechanical Electrical

• Battery case, posts, hold-down clamp, cables and connections
• Generator drive (serpentine) belt for condition and tension to make sure there is no slip between the belt and the pulley. For additional information, refer to Section 303-05 .
• Battery charge
• Generator pulley

• Battery junction box (BJB)Mega Fuse
• Battery junction box fuse:
  • 11 (20A)
• Central junction box (CJB) fuse:
  • 30 (30A)
• Circuitry
• Charging system warning indicator
• Cables

1. Check the operation of the charging system warning indicator lamp (instrument cluster). Normal operation is as follows:
   • With the ignition switch OFF, the charging system warning indicator should be OFF.
   • With the ignition switch in RUN and the engine off, the charging system warning indicator light should be on.
   • With the engine running, the charging system warning indicator light should be off.

1. Verify the battery condition. Refer to Section 414-01 .

Normal Charging System Voltages and Charging System Warning Indicator Operation Ignition Switch Position A Circuit 35 (OG/LB) S Circuit 4 (WH/BK) I Circuit 904 (LG/RD) Generator B+ Circuit 38 (BK/OG) Battery Engine to Battery Ground Charging System Warning Indicator Operation OFF 12 volts 0 volts 0 volts 12 volts 12 volts 0 volts Off RUN-engine off 12 volts 0 volts 1-3 volts 12 volts 12 volts 0 volts Illuminated RUN-engine running 13-
15 volts 1/2 battery voltage 13-
15 volts 13-
15 volts 13-
15 volts 0 volts Off

1. If the customer concern is verified after the initial inspection, refer to the Symptom Chart to determine which tests to carry out.
2. • The charging system warning indicator is on with the engine running (the system voltage does not increase)
   • Circuitry.
   • Voltage regulator.
   • Generator.
   • GO to Pinpoint Test B .
   Your whole problem is the alternator is not charging , a couple tests with a volt meter would tell you !

Generally that indication implies generator failure. Generator failure can come in multiple forms. A faulty ground will cause the generator not to charge and potentially burn it up. A severed phase wind (remember, your alternator is really a three-phase generator with a six pulse front end rectifier set) will cause the light to intermittently come on along with weak charging output. A voltage regulator failure will cause zero field current in the rotor. A brush failure will also cause a generator failure light to come on and stay on. A rectifier failure (any of the six) will cause the generator not to charge properly and turn on the MIL and generator failure indicator (looks like a battery). The condition of the battery can also cause generator failure, if the battery is defective (buckled plates, weak electrolyte, low water, etc.) it will place a very high load on the generator continuously, causing it to 'full field' the rotor which can cause the rotor to overheat and fail. Never run a generator without the battery terminals connected as this will cause it to fail quite spectacularly. Do not attempt to verify output of the generator with the battery terminal leads disconnected.

If generator failure is indeed the cause, find out why. Generators rarely fail. When they do, it usually is caused by poor ground connections, corroded battery terminals, high continuous loads, electrical faults and poorly-wired ancillary equipment, such as head units, amplifiers, inverters, etc. Always check all these out when replacing the generator. Never run a generator without the battery terminals connected as this will cause it to fail quite spectacularly.

Take it back to the dealer and have it fixed, the charging system does have a fault.

Charging System Failure
Refer to Charging System Description and Operation

Electrical Power Management (EPM) Overview
The EPM system is designed to monitor and control the charging system and send diagnostic messages to alert the driver of possible problems with the battery and generator. This EPM system primarily utilizes existing on-board computer capability to maximize the effectiveness of the generator, to manage the load, improve battery state-of-charge (SOC) and life, and minimize the system's impact on fuel economy. The EPM system performs three functions:
• It monitors the battery voltage and estimates the battery condition.
• It takes corrective actions by adjusting the regulated voltage.
• It performs diagnostics and driver notification.
The battery's condition is estimated during key-off and during key-on. During key-off the SOC of the battery is determined by measuring the open-circuit voltage. The SOC is a function of the acid concentration and the internal resistance of the battery, and is estimated by reading the battery open circuit voltage when the battery has been at rest for several hours.
The SOC can be used as a diagnostic tool to tell the customer or the dealer the condition of the battery. Throughout key-on the algorithm continuously estimates SOC based on adjusted net amp hours, battery capacity, initial SOC, and temperature.
While running, the battery's degree of discharge is primarily determined by a battery current sensor, which is integrated to obtain net amp hours.
In addition, the EPM function is designed to perform regulated voltage control (RVC) to improve battery SOC, battery life, and fuel economy. This is accomplished by using knowledge of the battery's SOC and temperature to set the charging voltage to an optimum battery voltage level for recharging without detriment to battery life.
The Charging System Description and Operation is divided into 3 sections. The first section describes the charging system components and their integration into the EPM. The second section describes charging system operation. The third section describes the instrument panel cluster operation of the charge indicator, driver information center messages and voltmeter operation.

Charging System Failure
The BCM and the ECM/PCM will send a class 2 message to the IPC for the CHARGING SYSTEM FAILURE message to be displayed. It is commanded ON when a charging system DTC is a current DTC. The message is turned off when the conditions for clearing the DTC have been met.

You need to have a full vehicle scan done. Not just engine code's . An to do this you need a professional scan tool , not auto zone or advance etc.. Your best bet , take it to a qualified repair shop.

Your charging system is computer controlled . Do you know what DTC'S - diagnostic trouble code's are ? This are all associated with the charging system inone way or another .
DTC B1327
DTC B1328
DTC B1516
DTC P0560
DTC P0562
DTC P0563
DTC P0615
DTC P0621
DTC P0622


https://www.motor.com/magazinepdfs/042010_09.pdf

Instead of guessing as to what the problems is have it diagnosed at a qualified repair shop . Electrical testing needs to be done , charging system out put testing . voltage drop test electrical circuits . A bad ground wouldn't cause the battery to go bad , not charge properly is about all . Was the battery tested before it was replaced ? load and capacity tested ? What's the voltage Measurement at the battery with the engine running ? If the battery failed as many times you said it did , without testing i would suspect a over charge condition .That would be a guess without testing. The charging system on your vehicle is computer controlled .
Battery Common Causes of Malfunction
A battery is not designed to last forever. With proper care, however, the battery will provide years of good service. If the battery tests good but still fails to perform well, the following are some of the more common causes:
• A vehicle accessory was left on overnight.
• The driving speeds have been slow with frequent stops (stop-and-go driving).
• The electrical load has exceeded the generator output (particularly with the addition of aftermarket equipment).
• Existing conditions in the charging system, including the following possibilities:
- An electrical short
- A slipping belt
- A bad generator
- A bad generator voltage regulator.
• The battery has not been properly maintained, including the following situations:
- A failure to keep the terminals tight
- A failure to keep the terminals clean
- A loose battery hold down.
• There are mechanical conditions in the electrical system, such as a short or a pinched wire, attributing to power failure.

usually caused by failed generator. Fix the generator and other lights will also extinguish. The car should jump start, but will not stay running without a charged battery. Recommend removing the generator and take to parts store for testing. Would you like instructions for removing generator?

Hope this is helpful, Ian

CHARGING
DESCRIPTION - CHARGING SYSTEM
The charging system consists of:
† Generator
† Decoupler Pulley (If equipped)
† Electronic Voltage Regulator (EVR) circuitry
within the Powertrain Control Module (PCM)
† Ignition switch (refer to the Ignition System section
for information)
† Battery (refer to the Battery section for information)
† Battery temperature sensor
† Voltmeter (refer to the Instrument Cluster section
for information)
† Wiring harness and connections (refer to the
Wiring section for information)
† Accessory drive belt (refer to the Cooling section
for more information)
OPERATION - CHARGING SYSTEM
The charging system is turned on and off with the
ignition switch. The system is on when the engine is
running and the ASD relay is energized. When the
ASD relay is on, voltage is supplied to the ASD relay
sense circuit at the PCM. This voltage is connected
through the PCM and supplied to one of the generator
field terminals (Gen. Source +) at the back of the
generator.
The generator is driven by the engine through a
serpentine belt and pulley or decoupler pulley
arrangement.
The amount of DC current produced by the generator
is controlled by the EVR (field control) circuitry
contained within the PCM. This circuitry is connected
in series with the second rotor field terminal
and ground.
A battery temperature sensor is used to sense battery
temperature. This temperature data, along with
data from monitored line voltage, is used by the PCM
to vary the battery charging rate. This is done by
cycling the ground path to control the strength of the
rotor magnetic field. The PCM then compensates and
regulates generator current output accordingly to
maintain system voltage at the targeted system voltage
based on battery temperature.
All vehicles are equipped with On-Board Diagnostics
(OBD). All OBD-sensed systems, including EVR
(field control) circuitry, are monitored by the PCM.
Each monitored circuit is assigned a Diagnostic Trouble
Code (DTC). The PCM will store a DTC in electronic
memory for certain failures it detects. Refer to
On-Board Diagnostics in the Electronic Control Modules(
Refer to 8 - ELECTRICAL/ELECTRONIC CONTROL
MODULES/POWERTRAIN CONTROL
MODULE - DESCRIPTION) section for more DTC
information.
The Check Gauges Lamp (if equipped) monitors:
charging system voltage, engine coolant temperature
and engine oil pressure. If an extreme condition
is indicated, the lamp will be illuminated. This is
done as reminder to check the three gauges. The signal
to activate the lamp is sent via the PCI bus circuits.
The lamp is located on the instrument panel.
Refer to the Instrument Cluster section for additional
information.
VOLTAGE REGULATOR
DESCRIPTION
The Electronic Voltage Regulator (EVR) is not a
separate component. It is actually a voltage regulating
circuit located within the Powertrain Control
Module (PCM). The EVR is not serviced separately. If
replacement is necessary, the PCM must be replaced.
OPERATION
The amount of DC current produced by the generator
is controlled by EVR circuitry contained within
the PCM. This circuitry is connected in series with
the generators second rotor field terminal and its
ground.
Voltage is regulated by cycling the ground path to
control the strength of the rotor magnetic field. The
EVR circuitry monitors system line voltage (B+) and
battery temperature or inlet air temperature sensor
(refer to Battery Temperature Sensor or Inlet Air
Temperature Sensor for more information). It then
determines a target charging voltage. If sensed battery
voltage is 325 mv or lower than the target voltage,
the PCM grounds the field winding until sensed
battery volage is 325 mv above target voltage. A circuit
in the PCM cycles the ground side of the generator
field up to 250 times per second (250Hz), but
has the capability to ground the field control wire
100% of the time (full field) to achieve the target
voltage. If the charging rate cannot be monitored
(limp-in), a duty cycle of 25% is used by the PCM in
order to have some generator output. Also refer to
Charging System Operation for additional information.
REMOVAL
The electronic voltage regulator is not a serviced
separately. If replacement is necessary, the PCM
must be replaced.