U1530 on Cadillac: How to Diagnose & Fix
K9 Body Control Module Lost Communication with M35P Window Motor Module - Passenger / M74P Window Motor - Passenger on LIN Bus
1 Cadillac model · 1 documented issue · $200-$900 repair
U1530 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)
U1530 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 U1530 mean on a Cadillac?
U1530 stands for "K9 Body Control Module Lost Communication with M35P Window Motor Module - Passenger / M74P Window Motor - Passenger on LIN Bus." The Body Control Module (K9) is the LIN master for the door/window motor modules. U1530 sets when the BCM stops receiving the expected LIN response frames from the passenger window motor module (M35P) or passenger window motor (M74P). GM groups it with the whole U1500-U15FF common-LIN family under one diagnostic procedure. It matters for parasitic-drain complaints because a LIN slave that will not answer, or that keeps re-driving the bus, prevents the BCM from completing its bus-quiet check and keeps the network — and therefore the modules on it — from entering sleep mode. On Cadillac it is documented across 1 model: XTS.
What are the most common causes of U1530?
The most common causes of U1530 are: Failed passenger window motor module / window motor with integrated LIN electronics, Open, shorted or high-resistance LIN circuit between the BCM and the passenger door module — commonly a broken wire in the door-jamb harness boot, Water intrusion or corrosion at the door connector or inside the door module, Loss of ignition/battery feed or ground to the window motor module, Body Control Module fault or software concern. The specific cause varies by vehicle.
How much does it cost to fix U1530 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 U1530 on a different make?
View U1530 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.