Alternator parmeters under system tab

This is my first post in years, possibly ever

I am having problems with the voltage output of my alternator. The engine is a 2008 Cadillac LC3 using an e67 pcm and the alternator is from the same year Cadillac. Basically the alternator has 3 wires for hook up. A 2 pin plug and the 3rd for the 12v + output. The alternator is grounded through the case to the engine. Have good grounds to engine and body. Have been running the car for years with no problems. "Ignorance is bliss" It appears that this is a newer style alternator which GM started using about 2007 that relies on the e67 pcm as a voltage regulator. Check the wiring from the E67 to the 2 pin plug and it appears correct.

Put the car on the dyno last week and the tuner showed me that the pcm voltage was low. I hooked up a 25 amp Odessey battery charger to the vehicle, because it has an Odessey battery, during the dyno session and everything proceeded well.

Got home and started to investigate the problem. When you first start the vehicle the alternator puts out 14.5 volts. After about 2 minutes the voltage drops to 13.0 The voltage that I read will go as low as 11.2 when read through my OBDII port while it always stays above 12.4 on my dash gauge when I turn on the headlights and radiator fans etc. I put in a new alternator and nothing changed. Searched the web and it appears the E67 gets help from the BCM to control the voltage output of the alternator. This engine is in a stand alone application and there is no BCM. Under the System tab on HP Tuners there is a section for Alternator parameters. I have attached a screen shot of this. I would like to set my alternator output to like 14.8 volts which seems to keep my OBDII voltage above 12.5 does anyone know how I should populate this data? I don't want to fry the pcm so am reluctant to make guesses. Hopefully someone has had the same problem and knows a solution.

Quote:

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Originally Posted by Bullwinkel

This is my first post in years, possibly ever

I am having problems with the voltage output of my alternator. The engine is a 2008 Cadillac LC3 using an e67 pcm and the alternator is from the same year Cadillac. Basically the alternator has 3 wires for hook up. A 2 pin plug and the 3rd for the 12v + output. The alternator is grounded through the case to the engine. Have good grounds to engine and body. Have been running the car for years with no problems. "Ignorance is bliss" It appears that this is a newer style alternator which GM started using about 2007 that relies on the e67 pcm as a voltage regulator. Check the wiring from the E67 to the 2 pin plug and it appears correct.

Put the car on the dyno last week and the tuner showed me that the pcm voltage was low. I hooked up a 25 amp Odessey battery charger to the vehicle, because it has an Odessey battery, during the dyno session and everything proceeded well.

Got home and started to investigate the problem. When you first start the vehicle the alternator puts out 14.5 volts. After about 2 minutes the voltage drops to 13.0 The voltage that I read will go as low as 11.2 when read through my OBDII port while it always stays above 12.4 on my dash gauge when I turn on the headlights and radiator fans etc. I put in a new alternator and nothing changed. Searched the web and it appears the E67 gets help from the BCM to control the voltage output of the alternator. This engine is in a stand alone application and there is no BCM. Under the System tab on HP Tuners there is a section for Alternator parameters. I have attached a screen shot of this. I would like to set my alternator output to like 14.8 volts which seems to keep my OBDII voltage above 12.5 does anyone know how I should populate this data? I don't want to fry the pcm so am reluctant to make guesses. Hopefully someone has had the same problem and knows a solution.

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I would like to know also.

I started this thread and done some additional research on Google and have more information concerning this subject. The response will be rather long. Hope someone reviews this for correctness and gives additional information about the parameters.

I will first enter the parameters that HP Tuners want populated and let you know how I think they should be populated. I have only changed a few of the parameters and am reluctant to do further changes at this time. FOLLOWING THE HP TUNERS PARAMERS IS WHAT I FOUND ON GOOGLE

Here are the HP TUNERS OPTIONS::::

[ECM] 740 - Alternator Voltage Control: Indicates the vehicle is fitted with a regulated voltage control alternator and serial message duty cycle control from BCM is available, if disabled DC will be 100% when alternator is enabled.
FITTED IS THE DEFAULT NOT FITTED IS WHAT I CHOSE BECAUSE I HAVE A STAND ALONE APPLICATION WITH NO BCM
************************************************** ***********************************
[ECM] 741 - Alternator ECM Override: Should only be enabled if Voltage Control is enabled. Indicates that the ECM can override the serial message alternator duty cycle to boost system voltage when required.
ENABLED IS THE DEFAULT DISABLED IS WHAT I CHOSE I THINK HP TUNERS SHOULD HAVE USED THE WORD FITTED AS A NOMENCLATURE INSTEAD OF "VOLTAGE CONTROL ENABLED, I THINK DISABLED IS CORRECT
************************************************** ***********************************
[ECM] 8155 - Alternator Serial Request Init: The serial message value is initialized to this prior to any alternator duty cycle serial messages being received.
85% IS THE DEFAULT AND THAT IS WHAT I USED

************************************************** ****************************
[ECM] 8150 - Alternator Override DC Max: Maximum Duty Cycle requested by override voltage.

90% IS THE DEFAULT AND THAT IS WHAT I USED

************************************************** ****************************

[ECM] 8160 - Alternator DC Min: Minimum Duty Cycle used as limit for default action.

36% IS THE DEFAULT AND I USED 50% PLEASE READ BELOW AND MAKE YOUR OWN JUDGEMENT ABOUT THIS AS NEAR AS I CAN TELL THIS PARAMETER IS TELLING THE PCM AT WHAT VOLTAGE YOU WANT YOUR BATTERY CHARGED. IT IS MY UNDERSTANDING THAT IF YOU GET THIS NUMBER TOO HIGH IT CAN OVERCHARGE YOUR BATTERY WHICH WILL OVERHEAT AND DAMAGE THE BATTERY. THERE IS A CHART BELOW THAT HAS A CORRELATION OF THIS NUMBER TO VOLTAGE THE WAY I UNDERSTAND IT. OEM APPLICATIONS THAT HAVE A BCM MONITOR THE BATTERY VOLTAGE.

************************************************** ****************************

ECM] 8161 - Alternator Default Time: Serial communications must be lost or duty cycle below minimum for this amount of time, before alternator duty cycle will be defaulted to 100%.

I USED THE DEFAULT OF 120 SECONDS. I HOPE SOMEONE THAT KNOWS THESE PARAMETERS REVIEWS THIS FOR CORRECTNESS. I DROVE MY HOT ROD FOR YEARS BEFORE KNOWING I HAD A VOLTAGE PROBLEM. IT WAS ONLY WHEN I PUT THE VEHICLE ON A DYNO THAT THE OPERATOR TOLD ME I HAD LOW VOLTAGE GOING TO THE PCM. AT THAT TIME ALL THE PARAMETERS FOR THE ALTERNATOR WERE THE FACTORY DEFAULTS WHICH THOUGHT THE VEHICLE HAD A BCM. WITH THOSE OEM SETTINGS MY ALTERNATOR APPEARED TO CHARGE AT 14.8 VOLTS 120 SECONDS WHEN I FIRST STARTED IT U

************************************************** ****************************

[ECM] 18100 - Alternator Startup Delay: The alternator will be disabled for this long at startup

FILL OUT CHART DEFAULT SEEMS OK



[ECM] 18101 - Alternator Cutout Stall RPM: If engine speed drops below this for a given desired idle speed, the alternator will be disabled to assist stall prevention.
FILL OUT CHART DEFAULT SEEMS OK

************************************************** ****************************

[ECM] 8140 - Alternator Max Stall Off Time: Maximum cumulative off time due to stall protect per key cycle.
THE DEFAULT OF 20 SECONDS SEEMS OK

************************************************** ****************************

[ECM] 8141 - Fuel System Voltage Delay: Startup delay before Minimum Fuel System Voltage will be requested.
THE DEFAULT OF 20 SECONDS SEEMS OK

************************************************** ****************************

[ECM] 18102 - Fuel System Minimum Voltage: Minimum voltage required by fuel system for proper operation.

CHART DEFAULT SEEMS LOW WENT TO 13.5

************************************************** ****************************

[CM] 8142 - Airflow System Minimum Voltage: Minimum system voltage required by airflow system.
DEFAULT OF 11.8 SEEMS LOW WENT TO 12.6

************************************************** ****************************

[ECM] 8144 - Diagnostic System Voltage Delay: Startup delay before Diagnostic Boost Voltage can be requested.
DEFAULT OF 20 SECONDS SEEMS OK

************************************************** ****************************

[ECM] 8143 - Diagnostic Minimum Voltage Low: Minimum system voltage required by diagnostic systems to trigger voltage boost logic.
DEFAULT 11.2 VOLTS SEEMS LOW WENT TO 12.5?


[ECM] 8145 - Diagnostic System Low Voltage Delay: Delay that system voltage must be low before Diagnostic Boost Voltage can be requested.

DEFAULT OF 5 SECONDS SEEMS OK

************************************************** ****************************

[ECM] 8147 - Diagnostic System Voltage Step: If system voltage remains low, Diagnostic Boost Voltage will be stepped up by this amount.

DEFAULT IS .2 VOLTS SEEMS OK IF UPDATE BY PARAMETER BELOW

************************************************** ****************************

[ECM] 8146 - Diagnostic System Voltage Step Delay: If system voltage remains low, Diagnostic Boost Voltage will be stepped up by Diagnostic System Voltage Step at this time interval.

DEFAULT IS 0.0 SECONDS IS THE HP TUNERS DEFAULT SHOULD BE OK

************************************************** ****************************

[ECM] 8148 - Diagnostic Boost Voltage: Minimum system voltage required by diagnostic systems
DEFAULT IS 12.8 VOLTS CHANGED TO 13.2

************************************************** ***********************************

[ECM] 8149 - Diagnostic Boost Voltage Max Time: Maximum time that Diagnostic Boost Voltage required by diagnostic systems can be requested.

DEFAULT SEEMED OK AT 600 SECONDS



DR44 Alternator Control



The engine control module (ECM) controls the generator through the generator turn on signal. It monitors the generator performance though the generator field duty cycle signal circuit. The signal is 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. The following table shows the commanded duty cycle and output voltage of the generator.

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 generator provides a feedback signal of the generator voltage output through the generator field duty cycle signal circuit to the ECM. This information is sent to the body control module (BCM). The signal is a 5 volt PWM signal of 128 Hz with a duty cycle of 0-100 percent. Normal duty cycle is between 5-99 percent. Between 0-5 percent and 100 percent are for diagnostic purposes.

Electrical Power Management (EPM) Overview

The electrical power management (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 and life, and minimize the system's impact on fuel economy. The EPM system performs 3 functions:

• It monitors the battery voltage and estimates the battery condition.
• It takes corrective actions by boosting idle speeds, and adjusting the regulated voltage.
• It performs diagnostics and driver notification.

The battery condition is estimated during ignition-off and during ignition-on. During ignition-off the state-of-charge (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 ignition-on, the algorithm continuously estimates SOC based on adjusted net amp hours, battery capacity, initial SOC, and temperature.

While running, the battery 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 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 (IPC) operation of the charge indicator, driver information center (DIC) messages, and voltmeter operation.


Charging System Components

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 GMLAN 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 field control 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 sends idle boost requests to the ECM.

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 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)
The ECM directly controls the generator field control circuit input to the generator. The ECM receives control decisions based on messages from the BCM. It monitors the generators generator field duty cycle signal circuit and sends the information to the BCM.

Instrument Panel Cluster (IPC)
The IPC provides a means of customer notification in case of a failure and a voltmeter. There are 2 means of notification, a charge indicator and the driver information center (DIC) SERVICE BATTERY CHARGING SYSTEM message.

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:
• Battery Sulfation Mode
• Charge Mode
• Fuel Economy Mode
• Headlamp Mode
• Start Up Mode
• Voltage Reduction Mode

The engine control module (ECM) controls the generator through the generator turn on signal. It monitors the generator performance though the generator field duty cycle signal circuit. The signal is 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. The following table shows the commanded duty cycle and output voltage of the generator:


Commanded Duty Cycle Generator Output Voltage
10% 11 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% 15.5 V

The generator provides a feedback signal of the generator voltage output through the generator field duty cycle signal circuit to the ECM. This information is sent to the body control module (BCM). The signal is a 5 volt PWM signal of 128 Hz with a duty cycle of 0-100 percent. Normal duty cycle is between 5-99 percent. Between 0-5 percent and 100 percent are for diagnostic purposes.

The alternator will work, but not to the full capacity that it should...hope this helps ya.

I know this is an old thread but here's some additional information that describes the operational modes.

Battery Sulfation Mode

The BCM will enter this mode when the interpreted generator output voltage is less than 13.2 V for 45 minutes. When this condition exists the BCM will enter Charge Mode for 2?3 minutes. The BCM will then determine which mode to enter depending on voltage requirements.

Charge Mode


The BCM will enter Charge Mode when ever one of the following conditions are met.
The wipers are ON for more than 3 seconds.

GMLAN (Climate Control Voltage Boost Mode Request) is true, as sensed by the HVAC control head. High speed cooling fan, rear defogger and HVAC high speed blower operation can cause the BCM to enter the Charge Mode.

The estimated battery temperature is less than 0?C (32?F).

Battery State of Charge is less than 80 percent.

Vehicle speed is greater than 145 km/h (90 mph)

Current sensor fault exists.

System voltage was determined to be below 12.56 V

When any one of these conditions is met, the system will set targeted generator output voltage to a charging voltage between 13.9?15.5 V, depending on the battery state of charge and estimated battery temperature.

Fuel Economy Mode

The BCM will enter Fuel Economy Mode when the estimated battery temperature is at least 0?C (32?F) but less than or equal to 80?C (176?F), the calculated battery current is less than 15 amperes and greater than −8 amperes, and the battery state-of-charge is greater than or equal to 80 percent. Its targeted generator output voltage is the open circuit voltage of the battery and can be between 12.5?13.1 V. The BCM will exit this mode and enter Charge Mode when any of the conditions described above are present.

Headlamp Mode

The BCM will enter Headlamp Mode when ever the headlamps are ON (high or low beams). Voltage will be regulated between 13.9?14.5 V.

Start Up Mode

When the engine is started the BCM sets a targeted generator output voltage of 14.5 V for 30 seconds.

Voltage Reduction Mode

The BCM will enter Voltage Reduction Mode when the calculated ambient air temperature is above 0?C (32?F). The calculated battery current is less than 1 ampere and greater than −7 amperes, and the generator field duty cycle is less than 99 percent. Its targeted generator output voltage is 12.9 V. The BCM will exit this mode once the criteria are met for Charge Mode.

Instrument Panel Cluster Operation


Charge Indicator Operation


The instrument panel cluster illuminates the charge indicator and displays a warning message in the driver information center if equipped, when the one or more of the following occurs:
The engine control module (ECM) detects that the generator output is less than 11 V or greater than 16 V. The instrument panel cluster receives a GMLAN message from the ECM requesting illumination.

The instrument panel cluster determines that the system voltage is less than 11 V or greater than 16 V for more than 30 seconds. The instrument panel cluster receives a GMLAN message from the body control module (BCM) indicating there is a system voltage range concern.

The instrument panel cluster performs the displays test at the start of each ignition cycle. The indicator illuminates for approximately 3 seconds.

Display Message: BATTERY NOT CHARGING SERVICE CHARGING SYSTEM or SERVICE BATTERY CHARGING SYSTEM


The BCM and the ECM will send a serial data message to the driver information center for the BATTERY NOT CHARGING SERVICE CHARGING SYSTEM or 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.

OP are you still around?
Have you fixed the problem?
How old is your car? Engine swapped?
Have you checked the volts at the battery and alternator?
It seems that volt readings through OBD2 ports / scanners in engine-swapped older cars = BS (show less than reality)

This thread has my interest as well.

I've been battling a blower motor issue in my '07 TBSS (E67). The blower will cycle on and off for the first few minutes the truck is running, then work normal.

Parameter 8241 is Airflow System Minimum Voltage: Minimum system voltage required by airflow system. Currently set at 12.

I've also noticed at times the volt gauge isn't on/past 14. Closer to 12.

Does 8241 act as a safety to turn off the blower if the operating voltage is low?

A 2007 E67 in Trailblazer SS shows "Fitted". 2008 and 2009 E67 in Trailblazer SS shows "Not Fitted". They have the same battery cable and alternator. What gives?

:bump:

interesting. I have a 08 vette that factory seems to be set to non fitted. but all the default values match above. it's pretty stock with all the bcm and stuff. wonder why it doesn't control the alt, and if it does, why is it set to not fitted and disabled.


wonder what it would do if I turned it on. these hot TX days in traffic idling at 650 rpms you can watch the alt drop off and run off 11ish volt battery. be nice if it would just idle the car up a bit to stay charging. for the life of me I can't find a voltage vs idle rpm table, or even a ac rpm adder, it's all tq based ac logic.

I do have the e38 ecm, not the e67. weird.

great thread
:bump:

Without the BCM feeding the serial input, the ([ECM] 8161 - Alternator Default Time) will max the Duty Cycle out to 100% after the default settings of 120 seconds have passed. By maxing this time (13,000,000 seconds), wouldn't it just keep the initial Duty Cycle rate set out by ([ECM] 8155 - Alternator Serial Request Ini) which default is 85%. In my case, 85% was charging at 14.8V and a rate of 80% gave me 14.4V. I'll give it a run today and see if the voltage still drops off after the 2 minute mark or if we have a winner.

I'm running the e38 ecm and no bcm.