U1524 on Cadillac: How to Diagnose & Fix
Lost Communication With Right Headlamp on LIN Bus
1 Cadillac model · 1 documented issue · $200-$900 repair
U1524 on Cadillac by model: symptoms, diagnosis and fix
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)
U1524 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 U1524 mean on a Cadillac?
U1524 stands for "Lost Communication With Right Headlamp on LIN Bus." A General Motors-specific network code. The headlamp control module (or headlamp leveling control module) stopped receiving the expected periodic message from the right headlamp over the LIN (Local Interconnect Network) bus — a single-wire, low-speed serial link between a master module and its subsystem devices. In practice the right headlamp, its leveling function, or its adaptive/DRL features may stop responding to commands. The lamp itself may still illuminate on a basic circuit even though the module can no longer talk to it. On Cadillac it is documented across 1 model: XTS.
What are the most common causes of U1524?
The most common causes of U1524 are: Failed LED headlamp assembly or its integrated driver/ballast module (the LIN node itself), Open, shorted, or corroded LIN serial data wire between the headlamp and the control module, Poor connection, water intrusion, or pushed-out pins at the headlamp connector, Loss of ignition power or ground to the right headlamp assembly, Faulty headlamp control module / headlamp leveling control module, Aftermarket headlamp or HID/LED retrofit that does not support LIN communication. The specific cause varies by vehicle.
How much does it cost to fix U1524 on a Cadillac?
Published repair estimates on Cadillac range from $200 to $900 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for U1524 on a different make?
View U1524 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.