B1446 on 2013-2017 Cadillac ATS: OnStar Backup Battery Failure Causes and Fixes

What's Unique About the 2013-2017 Cadillac ATS

It is critical to know that this is a GM-specific code definition. On many other vehicle brands, such as Toyota, code B1446 refers to an HVAC system fault with an air mix damper. On the Cadillac ATS and other GM vehicles, however, it is exclusively tied to the telematics (OnStar) system. The backup battery is a non-rechargeable component with a finite service life, making this code a common issue as these vehicles age. This issue is widespread across dozens of GM models from various years, as documented in multiple revisions of TSB PIC4541.

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• Red indicator light on the OnStar buttons (rearview mirror)
• Message on the Driver Information Center (DIC) regarding OnStar service
• Inability for the OnStar system to function
• Inability to connect to the OnStar center when pressing the blue or red buttons

Most Likely Causes

1. Aged/Failed OnStar Backup Battery 🔴 High Probability → Shop Vehicle Battery The backup battery is a non-rechargeable lithium unit designed to last several years. Once its voltage drops below a specific threshold due to age or a single activation event, it must be replaced. This is a normal wear-and-tear item.
   How to confirm: Confirm the presence of code B1446 with a compatible OBD-II scanner and a red OnStar LED. The battery itself is the most likely point of failure. An OnStar advisor can also remotely diagnose the battery failure.
   Typical fix: Replace the OnStar communication backup battery module. It is critical to disconnect power only when the ignition is OFF and Retained Accessory Power (RAP) has timed out (usually by opening the driver's door) to avoid permanently damaging the new battery.
   Est. part cost: $40-$90

Rare But Worth Checking

• Wiring Harness Damage: Damage to the wiring leading to the Telematics Communication Interface Control Module (OnStar Module) could prevent the backup battery from being recognized, though this is uncommon.
• Faulty Telematics Communication Interface Control Module (VCIM): → Shop Telematics Interface Module In rare cases, the main OnStar module itself could be faulty, not the battery. This is more likely if other OnStar-related codes, like B1000 or U1500, are also present. A failing VCIM can also sometimes cause a parasitic drain on the main vehicle battery.

Diagnosis Steps

1. Verify the trouble code with an OBD-II scanner capable of reading Body (B) codes.
2. Check the status of the OnStar indicator light on the rearview mirror. A solid red light corresponds with this fault.
3. IMPORTANT: Turn the ignition OFF. Open the driver's door to ensure Retained Accessory Power (RAP) is disabled. Failure to do this before disconnecting power can instantly and permanently destroy the new backup battery.
4. Access the trunk and fold down the rear seats.
5. Remove the rear deck trim and side sail panels to gain access to the OnStar module (VCIM), which is mounted under the rear package shelf.
🎬 Watch: How to access and remove the OnStar module
6. Inspect the wiring and connectors to the module for any visible damage.
7. The backup battery is a small module connected to the main VCIM. Disconnect the old battery module and connect the new one.
8. Reassemble the trim panels and seats.
9. Clear the trouble code using the scanner and turn the ignition on. Verify the OnStar light turns green after its initial check, indicating a successful repair.

Parts You'll Likely Need

• OnStar Communication Backup Battery Module (OEM #23117460) — This is the component that houses the non-rechargeable backup battery. The entire module is typically replaced as a unit. This part number is confirmed for various GM models from the era.
  Trusted brands: ACDelco, GM Genuine Parts
  OEM price range: $60-$100
  Aftermarket price range: $40-$70 (Used/Remanufactured)

Related Codes That Often Appear With This One

• B1447 — This code is also listed in TSB #PIC4541F as an indicator of OnStar back-up battery failure ('Backup Power Source Open Circuit') and may appear alongside B1446.
• B1000 — On the Cadillac ATS, a B1000 code can indicate a general electronic control unit failure, and the OnStar module is a common culprit that sets this code, sometimes due to internal faults beyond just the battery.

Technical Service Bulletins (TSBs) & Recalls

• PIC4541F: Directly links DTC B1446 and B1447 to OnStar back-up battery failure and a red LED light. It warns technicians not to disconnect power while the ignition or RAP is active.
• PIC4541E, PIC4541D, PIC4541A: Earlier revisions of the same TSB, showing the long history of this issue across a vast number of GM vehicles, including Buick, Chevrolet, Pontiac, and Saturn models dating back to 2006.

Platform-Specific Known Issues

• The OnStar backup battery is a known service item with a finite life, as stated in GM service bulletin #PIC4541F. Its failure is a matter of when, not if.
• It is critical to disable Retained Accessory Power (RAP) by opening a door after turning the ignition off before starting the replacement. Disconnecting the module while it is powered, even with the key off, will trigger the new battery's one-time activation, permanently ruining it.

Scan Tool Commands That Help

• GDS2/Tech2/SPS: VCIM Vehicle Communication Interface Module Set-up — This Service Programming System (SPS) function is required after replacing the main OnStar module (VCIM) to program it for the specific vehicle. This is generally not needed for just a backup battery replacement, but is critical if the entire module is swapped.
• GDS2/Tech2/SPS: ONSA-OnStar Activation / ONSU-OnStar Set-up and Activation — After replacing and setting up a new VCIM, this SPS function sends the new module's data to OnStar to activate the subscription. For 2010+ vehicles, this is combined into a single 'ONSU' function. This is not required for a simple backup battery swap, but is mandatory for a full VCIM replacement to restore service.

Wiring & Ground Locations

• K73 Telematics Communication Interface Control Module Connector X1 — On the OnStar VCIM module, which is located under the rear package shelf in the trunk.. This is the main 16-pin connector for the OnStar module. Checking for power and ground at this connector is a key step if a new backup battery does not solve the problem.
• Connector X1, Pin 5 — On the 16-pin connector for the OnStar module (VCIM).. This pin provides Battery Positive Voltage to the module, fed by a Red/Gray wire. A loss of voltage here would indicate a wiring or fuse issue upstream from the module.
• Connector X1, Pins 6 and 7 — On the 16-pin connector for the OnStar module (VCIM).. These pins are the primary grounds for the module, using Black wires. A bad ground connection can cause various OnStar faults, including communication issues with the backup battery.

Real Owner Repair Stories

• cadillacforums.com user (2014 Cadillac CTS (platform mate)) — Original battery was 7 years old and causing starting issues in cold weather. After dealer replaced the main vehicle battery, the OnStar system malfunctioned and HVAC vents stopped working correctly.
  ❌ Tried (didn't work) The user suspected the dealer caused the issue during the main battery replacement.
  ✅ What actually fixed it The user's primary complaint was an HVAC issue that occurred after the main battery was replaced, a common problem where blend door actuators need recalibration. However, they explicitly mention the risk of the OnStar backup battery failing if the main battery is replaced incorrectly, which is the direct cause of code B1446. This story highlights the procedural sensitivity of any battery service on these cars.

OEM Part Supersession History

• 23117460 → 84548349 — Standard part lifecycle update. The new part number is the current service replacement.
  Heads up: No known incompatibilities. 84548349 is the direct, backward-compatible replacement for 23117460 for this application.