PCM controlled charge voltage

[RD_Atlanta]

It appears the desired Commanded Duty Cycle PWM % is a tunable parameter on some PCMs while not on others. Does anyone know if there is a way to adjust the charge output voltage on the PCM OS's where this commanded duty cycle % is not accessible & adjustable?

Commanded Duty Cycle Generator Output Voltage:

10% 11.00 V
20% 11.56 V
30% 12.12 V
40% 12.68 V
50% 13.25 V
60% 13.81 V
70% 14.37 V
80% 14.94 V
90% 15.50 V

 

[ulycyc]

You need to check with companies that make reprogramming software but I doubt it will on a 2005 Lesabre. The Corvette and "V" option Caddie's pcm's have most if not all parameters adjustable.

 

[RD_Atlanta]

You need to check with companies that make reprogramming software but I doubt it will on a 2005 Lesabre. The Corvette and "V" option Caddie's pcm's have most if not all parameters adjustable.

I have several software packages but they are limited to what the PCM OS supports. I was hoping there might be an alternative method. It's a mystery why all of the PCM OSes do not support adjusting the alternator PWM.

 

[ulycyc]

They do make stand alone volt booster/trimmers that go inline at the alternator and controlled by the TPS. I know Caspers electronics make a few.

 

[RD_Atlanta]

They do make stand alone volt booster/trimmers that go inline at the alternator and controlled by the TPS. I know Caspers electronics make a few.

Thanks.

 

[BuickGirlFromMars]

It appears the desired Commanded Duty Cycle PWM % is a tunable parameter on some PCMs while not on others. Does anyone know if there is a way to adjust the charge output voltage on the PCM OS's where this commanded duty cycle % is not accessible & adjustable?

Commanded Duty Cycle Generator Output Voltage:

10% 11.00 V
20% 11.56 V
30% 12.12 V
40% 12.68 V
50% 13.25 V
60% 13.81 V
70% 14.37 V
80% 14.94 V
90% 15.50 V

The alternator is the thing controlling the charge. The pcm doesn’t dictate it here

 

[RD_Atlanta]

Attached is the charging circuit schematic for the 2000-2005 Buick LeSabre. Below is a summary for the charge circuit control-scheme used on the 2000-2005 LeSabre.

The 2000-2005 Buick LeSabre uses a PWM (Pulse Width Modulation) signal between the PCM (Powertrain Control Module) and the alternator to enable variable voltage charging, allowing the PCM to precisely control the battery's charging voltage (Vset) for better battery health, optimal engine efficiency (by reducing alternator drag), and system management, rather than a fixed voltage. This PWM signal, a series of 5V pulses at ~128Hz, tells the alternator's internal regulator how much to charge, with longer "on" times meaning higher voltage, adapting to battery needs and electrical load.

How it Works:

PCM Senses: The PCM monitors battery voltage, electrical load, engine RPM, and alternator output.
PCM Calculates: It determines the ideal charging voltage (Vset) for current conditions (e.g., colder battery needs higher voltage, heavy loads need more power).
PCM Commands: It sends a PWM signal (duty cycle) to the alternator's field circuit.
Alternator Responds: The alternator's regulator interprets the duty cycle (percentage of "on" time) to adjust the magnetic field strength, thereby changing the output voltage.

One closing point: All supporting GM literature indicates that (on the Lesabre's) the PCM handles the charging I/O (Feedback, PWM Output & Charge Permissive) and the closed loop logic. However I <suspect> the closed loop logic 'might' reside in the Dash Integration Module (DIM), but I'm not yet certain if this is the case. Regardless, the information between the (2) modules is via the class-2 J1850vpw bus and the real-time charge voltage is then passed from the DIM to the IPC to be displayed (for DIC equipped LeSabre models) also via the class-2 J1850vpw bus.

 

[BuickGirlFromMars]

Attached is the charging circuit schematic for the 2000-2005 Buick LeSabre. Below is a summary for the charge circuit control-scheme used on the 2000-2005 LeSabre.

The 2000-2005 Buick LeSabre uses a PWM (Pulse Width Modulation) signal between the PCM (Powertrain Control Module) and the alternator to enable variable voltage charging, allowing the PCM to precisely control the battery's charging voltage (Vset) for better battery health, optimal engine efficiency (by reducing alternator drag), and system management, rather than a fixed voltage. This PWM signal, a series of 5V pulses at ~128Hz, tells the alternator's internal regulator how much to charge, with longer "on" times meaning higher voltage, adapting to battery needs and electrical load.

How it Works:

PCM Senses: The PCM monitors battery voltage, electrical load, engine RPM, and alternator output.
PCM Calculates: It determines the ideal charging voltage (Vset) for current conditions (e.g., colder battery needs higher voltage, heavy loads need more power).
PCM Commands: It sends a PWM signal (duty cycle) to the alternator's field circuit.
Alternator Responds: The alternator's regulator interprets the duty cycle (percentage of "on" time) to adjust the magnetic field strength, thereby changing the output voltage.

One closing point: All supporting GM literature indicates that (on the Lesabre's) the PCM handles the charging I/O (Feedback, PWM Output & Charge Permissive) and the closed loop logic. However I <suspect> the closed loop logic 'might' reside in the Dash Integration Module (DIM), but I'm not yet certain if this is the case. Regardless, the information between the (2) modules is via the class-2 J1850vpw bus and the real-time charge voltage is then passed from the DIM to the IPC to be displayed (for DIC equipped LeSabre models) also via the class-2 J1850vpw bus.

This is incorrect.
I wish you werent confidently asserting things that arent true. While I dont doubt that maybe the PCM is capable of doing what youre saying based on the fact you found the fields in the PCM on a tuner software, , here is the service data for the Lesabre:



THen the DIM can interact with it this way:


There is nothing inaccurate about your diagram you posted but you are interpreting the Duty Cycle wire as one of the control wires

 

[BuickGirlFromMars]

I


Cars with the setup youre envisioning wont be using a sense wire to the regulator and the regulator likely only has 2 wires on them, if equipped.
IT appears the Caddys in 2004 MAY do what you sought, but thats a different PCM im pretty sure

 

[DrivenDaily]

Dang! Defeated by facts!

Way to go, BGFM! Refuting know-it-alls by actually knowing more. Good job!