iboughtatahoe23
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- Feb 17, 2023
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Hey everyone,
I’m running into a frustrating overnight battery drain on my Tahoe (factory Bose, non-touchscreen, UQA RPO code) and could use some insight from anyone familiar with how these GMT900 trucks handle their electrical networks.
The Setup:
Subs/Box: CT Sounds Tropo dual 10” ported enclosure
Amp: CT-1500.1D monoblock (tuned safely to 30V / ~900W RMS via 40Hz tone)
LOC: CT-LC2 active line output converter tapped straight into all 4 factory sub harness wires.
Remote Turn-on: Tapped into the yellow wire on X14 pin 8 in the MBEC under the dash → LC2 REM IN → jumper from LC2 REM OUT to the amp.
Grounds: Amp is grounded to the rear cupholder stud area; LC2 is grounded to the driver seat bolt.
Battery: Walmart DieHard (brand new this past winter).
The Problem:
System has been running flawlessly for about 3–4 weeks—absolutely hits hard and clean. However, a few days ago the truck started dying overnight. I unhooked my plug-in AFM disabler and dash cam, let the truck sit for just two hours, and came back out to a slow crank. If it sits any longer, it’s completely dead.
The Tricky Part (RVC & RAP):
I know these Tahoes use Regulated Voltage Control (RVC) and Retained Accessory Power (RAP), which makes basic testing a nightmare.
I had the battery and alternator tested on my scanner . It said it tested OK but noted the alternator was "overcharging" (it was hitting around 14.86v) Because of the GM variable voltage system, I know it is completely normal during the ECM's "Startup Mode" to replenish the battery, so I don't think the alternator is actually cooked.
On the RAP side, I do get the normal 10–15 second phantom power-on and a subtle sub thump when opening the doors before starting the vehicle, which tells me the BCM data lines are waking up the factory amp/signals normally.
When the truck is off, the physical blue/red lights on my amp and my bass knob go dark like they should. However, because the BCM data bus can take 10–20 minutes to completely fall asleep, I’m worried something is staying awake quietly or grabbing "ghost voltage" from that MBEC accessory wire.
Before I lock the truck down, clamp the hood latch shut, and perform a 30-minute delayed parasitic draw test with my multimeter across the negative terminal, has anyone experienced a similar issue with an active LOC or the MBEC accessory circuit on these trucks? Could a failing internal sensing circuit in the converter be drawing power silently without triggering the amp's remote line?
Appreciate any advice or experiences with these charging systems!
I’m running into a frustrating overnight battery drain on my Tahoe (factory Bose, non-touchscreen, UQA RPO code) and could use some insight from anyone familiar with how these GMT900 trucks handle their electrical networks.
The Setup:
Subs/Box: CT Sounds Tropo dual 10” ported enclosure
Amp: CT-1500.1D monoblock (tuned safely to 30V / ~900W RMS via 40Hz tone)
LOC: CT-LC2 active line output converter tapped straight into all 4 factory sub harness wires.
Remote Turn-on: Tapped into the yellow wire on X14 pin 8 in the MBEC under the dash → LC2 REM IN → jumper from LC2 REM OUT to the amp.
Grounds: Amp is grounded to the rear cupholder stud area; LC2 is grounded to the driver seat bolt.
Battery: Walmart DieHard (brand new this past winter).
The Problem:
System has been running flawlessly for about 3–4 weeks—absolutely hits hard and clean. However, a few days ago the truck started dying overnight. I unhooked my plug-in AFM disabler and dash cam, let the truck sit for just two hours, and came back out to a slow crank. If it sits any longer, it’s completely dead.
The Tricky Part (RVC & RAP):
I know these Tahoes use Regulated Voltage Control (RVC) and Retained Accessory Power (RAP), which makes basic testing a nightmare.
I had the battery and alternator tested on my scanner . It said it tested OK but noted the alternator was "overcharging" (it was hitting around 14.86v) Because of the GM variable voltage system, I know it is completely normal during the ECM's "Startup Mode" to replenish the battery, so I don't think the alternator is actually cooked.
On the RAP side, I do get the normal 10–15 second phantom power-on and a subtle sub thump when opening the doors before starting the vehicle, which tells me the BCM data lines are waking up the factory amp/signals normally.
When the truck is off, the physical blue/red lights on my amp and my bass knob go dark like they should. However, because the BCM data bus can take 10–20 minutes to completely fall asleep, I’m worried something is staying awake quietly or grabbing "ghost voltage" from that MBEC accessory wire.
Before I lock the truck down, clamp the hood latch shut, and perform a 30-minute delayed parasitic draw test with my multimeter across the negative terminal, has anyone experienced a similar issue with an active LOC or the MBEC accessory circuit on these trucks? Could a failing internal sensing circuit in the converter be drawing power silently without triggering the amp's remote line?
Appreciate any advice or experiences with these charging systems!
