Fluctuating voltage on '07 Denali

[ToddEdge]

I recently bought a '07 Yukon Denali for trips and towing our boat to the lake. I took the first descent trip with it this weekend and noticed something that I thought was odd. When driving around the city, stop lights, ect, the voltage is slightly over 14 volts on my gauge. Once I've been on the highway for some time, I noticed the voltage shows well under 14 volts, probably around 12.8-13. Is this something problematic or does GM have some kind of intelligence built into the voltage system to adjust based on speed?

Thanks,
Todd

 

[sumo]

our charging system has the ability to change. The Pcm will determine how much demand is needed from the alternator. Mine does that too.

 

[ToddEdge]

our charging system has the ability to change. The Pcm will determine how much demand is needed from the alternator. Mine does that too.

Great, thank you. I was hoping I wasn't going to be buying an alternator this week...

Regards,
Todd

 

[ndirish39]

there are six modes it uses to charge the battery

Battery Sulfation Mode
The BCM will enter this mode when the interpreted generator output voltage is less than 13.2 volts 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.
• The 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 volts
• Tow/Haul mode is enabled
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 volts,
depending on the battery state of charge and estimated battery temperature.

Fuel Economy Mode
The BCM will enter Fuel Economy Mode when the ambient air 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 amps and greater than -8 amps, and the battery state of charge (SOC) 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 volts. 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 the headlamps are ON. Voltage will be regulated between 13.9-14.5 volts

Start Up Mode
When the engine is started the BCM sets a targeted generator output voltage of 14.3 volts for 30 seconds.
Voltage Reduction Mode

The BCM will enter Voltage Reduction Mode when the calculated battery temperature is above 0°C (32°F). The calculated battery current is
less than 1 amp and greater than -7 amps, and the generator field duty cycle is less than 99 percent. Its targeted generator output voltage is 13
volts. The BCM will exit this mode once the criteria are met for Charge Mode.

 

[wreedps]

does the above apply to 2005 Tahoes/

 

[NathanJax]

does the above apply to 2005 Tahoes/

nope

 

[richborba1]

I noticed my 07 Tahoe going that too but it drops in between 9 and 14. Is that normal?

 

[NathanJax]

I noticed my 07 Tahoe going that too but it drops in between 9 and 14. Is that normal?

Yup

 

[Bill-H]

Interesting. Thank you for the info

 

[01Konvict]

My 2011 Yukon Denali fluctuates between 12-14 depending on random times driving it. I cleaned the interior really good and had all the doors open for 4 hours and battery was dead when I tried to start it. Also was programming the ECM/TCM and low voltage warning came on. Is this stuff normal on these newer Denalis?