Some 2025-2026 Tahoe, Suburban, Yukon and Escalade models may experience a low or dead battery. During battery draw diagnostics, a 550 ma draw may be found, and which can be eliminated by removing a Body Control Module (BCM) fuse.
These conditions may be caused by unwanted voltage fluctuating on the sunshade lamp supply circuits from the overhead console (A103 Roof Console). (Fig. 5) The overhead console may see the voltage fluctuation as a new input each time the voltage dips low, resulting in the BCM staying active and causing the low battery charge condition.
Fig. 5
If these conditions are present, back probe the left (4785 LH) and right (2369 RH) sunshade lamp voltage supply circuits (Fig. 6) to ground at the overhead console using a Digital Multimeter while the sunshade mirror lamps are off/closed. A normally operating sunshade circuit should show a steady 12 volts when the sunshade mirror lamps are off/closed and then drop low and quickly recover back to 12 volts when the lamps are on/opened.
Fig. 6
If voltage is found to be fluctuating from approximately 2–12 volts on either circuit while the sunshade mirror lamps are off/closed, disconnect the sunshade and check for draw. After 10 minutes, if the excessive draw has dropped to an acceptable level, replace the sunshade.
TIP: It is important to wait approximately 10 minutes after any BCM LIN device fuses are removed during battery draw testing to allow the BCM to enter the sleep cycle. Pulling new fuses before waiting 10 minutes will keep the BCM awake or reset the BCM wake-up timer.
Refer to #PIT6427 for more details.
– Thanks to Ted Luczak
