U1540 on 2013-2019 Cadillac XTS (Luxury, Premium, Platinum, V-Sport, Vsport) — Body Control Module Lost Communication With Right Rear Window Motor on LIN Bus
1 vehicles · 1 makes · $200-$900 repair
How to diagnose and fix U1540: most-reported vehicles
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Cadillac XTS · 2013–2019
XTS owners frequently report the 12V battery going dead overnight or after a few days of sitting, caused by a control module failing to enter sleep mode and continuing to draw current with the ignition off. Common culprits on this platform include the radio/CUE (infotainment) module and the BCM. Repeated deep discharges then prematurely kill the battery and can trigger low-state-of-charge warnings and start-stop faults. GM issued service information for low-battery-state-of-charge conditions on 2018-2019 XTS/ATS/CTS.
Common Symptoms
- Battery dead after sitting overnight or a few days
- Repeated no-start / jump-start needed
- Battery Saver Mode message
- Low battery / reduced electrical features warnings
- Start-stop system inoperative
How to Fix
Perform a parasitic-draw test (normal is under ~50mA once modules sleep, roughly 30-40 seconds after lockup) and pull-fuse isolation to find the circuit that stays awake. Common fixes include replacing/reflashing a faulty CUE/radio module or BCM, repairing a chattering switch/connector that wakes the bus, and removing non-OEM accessories (aftermarket LEDs are a documented trigger). Replace the battery if it has been repeatedly deep-cycled.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- 12V AGM Battery (Group 48 / H6) — main battery, trunk-mountedOEMACDelco 48AGM (GM/ACDelco SKU 88864541)Cross-refInterstate MTZ-48/H6 Platinum Plus AGM, Duralast Platinum AGM Group 48/H6, EverStart Platinum AGM Group H6/48$200–$425
This is the one part in this repair that is reliably needed and reliably identifiable. A module that will not sleep deep-cycles the battery, and a deep-cycled AGM does not recover — so after the draw is found and fixed, the battery almos…
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Sources for this issue (1)
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U1540 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does U1540 mean?
U1540 stands for "Body Control Module Lost Communication With Right Rear Window Motor on LIN Bus." Manufacturer-specific (General Motors — Buick, Cadillac, Chevrolet, GMC). The body control module stopped receiving the supervised periodic messages it expects from the right rear power window motor module over the single-wire LIN serial data bus. The usual symptom is the right rear window not responding to the switch, working intermittently, or losing its express-up/anti-pinch function. It is a comfort-system fault, not a drivability or safety fault.
What are the most common causes of U1540?
The most common causes of U1540 are: Failed right rear window motor / regulator module, Open, short, or high resistance in the LIN circuit to the door, Damaged wiring in the door-jamb harness boot from repeated door movement, Corroded or backed-out connector terminals at the motor or door module, Loss of battery power or ground to the window motor module, Faulty body control module. The specific cause varies by vehicle.
How much does it cost to fix U1540?
Repair costs for U1540 range from $200 to $900, depending on the vehicle and root cause.
Which vehicles are affected by U1540?
Au7o has documented U1540 across 1 vehicle models from 1 manufacturers: Cadillac.
Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.