B1446 on 2013-2017 Buick Regal: OnStar Backup Battery Failure Causes and Fixes

What's Unique About the 2013-2017 Buick REGAL

It is critical to understand that B1446 is a manufacturer-specific code. On General Motors vehicles like your Buick Regal, it exclusively points to the OnStar backup battery. On other brands, such as Toyota or Lexus, the same code number refers to a completely unrelated part: an HVAC air mix damper servo motor. Furthermore, GM has issued specific warnings via Technical Service Bulletins (TSBs) stating that disconnecting the main vehicle battery while the ignition is on or Retained Accessory Power (RAP) is active can trigger the backup battery system, causing it to fully and permanently discharge. This issue is common across the GM Epsilon II platform on which the Regal is based.

Diagnostic Flowchart

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

Symptoms You May Notice

• A persistent red LED light on the OnStar buttons (typically on the rearview mirror or overhead console)
• A "Service OnStar" message appearing on the Driver Information Center (DIC)
• Inability to connect to OnStar services when pressing the blue button.

Most Likely Causes

1. OnStar Backup Battery End of Life 🔴 High Probability → Shop Vehicle Battery The backup battery is a non-rechargeable lithium battery with a finite service life, typically lasting 3-7 years. As these vehicles have aged, failure of the original battery is an expected maintenance item.
   How to confirm: Confirm the presence of code B1446 (and possibly B1447) using a scanner that can read Body (B) codes. The red OnStar LED is also a strong indicator. An OnStar advisor can also run a remote diagnostic to confirm the battery has failed.
   Typical fix: Replace the OnStar backup battery module. 🎬 Watch: See how to replace the battery on a 2015 Regal. The module is located in the trunk on the driver's side, behind the trunk liner.
   Est. part cost: $40 - $80
2. Premature Battery Discharge from Improper Service ⚪ Low Probability → Shop Vehicle Battery Per TSB #PIC4541F, disconnecting the main vehicle battery or OnStar fuse while the ignition is on or RAP is active will trigger the backup battery, causing it to fully and permanently discharge. This is a design feature to enable emergency calls after a crash, but it can be inadvertently triggered during service.
   How to confirm: This is difficult to confirm directly but is the likely cause if the B1446 code appears immediately after the vehicle was serviced, jump-started, or the main battery was replaced.
   Typical fix: Replace the OnStar backup battery, ensuring the proper power-down procedure is followed to prevent a repeat failure.
   Est. part cost: $40 - $80

Diagnosis Steps

1. Verify the trouble code using an OBD-II scanner capable of reading Body (B) codes. Look for B1446 with a symptom byte of '03'.
2. Check the status of the OnStar LED on the rearview mirror. A solid red light strongly corroborates the code.
3. CRITICAL TSB WARNING: Before attempting replacement, turn the ignition completely OFF. Open and close the driver's door to cancel Retained Accessory Power (RAP) and wait at least two minutes for all modules to power down. Failure to do this will activate and permanently destroy the new backup battery upon connection.
4. Locate the OnStar/VCIM module. In the 2013-2017 Regal, this is found in the trunk, behind the liner on the driver's side. You will need to remove the plastic trim and pull back the carpet liner to access it.
5. Disconnect the electrical connector(s) from the module. There may be a small tab you need to depress to release the connector.
6. The battery is often in a small plastic housing attached to the module or nearby. Unclip or unscrew the old battery from its mounting.
7. Install the new battery, reconnect the module, and reassemble any removed trim.
8. Clear the DTCs with a scan tool. The red light should turn green after the next ignition cycle and successful connection to the OnStar network. No reprogramming is needed for a battery change.

Parts You'll Likely Need

• OnStar Backup Battery (OEM #13509859, 13583673, 23117460, 88861186) — This is the direct cause of the fault code. It is a non-rechargeable battery that fails with age and is considered a maintenance item. GM has used several part numbers over the years that are interchangeable for this application.
  Trusted brands: ACDelco, Ultralife
  OEM price range: $50-$80
  Aftermarket price range: $40-$60

Related Codes That Often Appear With This One

• B1447 — B1446 is for 'Voltage Below Minimum Threshold', while B1447 indicates an 'Open Circuit'. They often appear together as the internal battery fails, and both point to the same root cause: a bad OnStar backup battery.

Technical Service Bulletins (TSBs) & Recalls

• PIC4541F: Diagnostic Tip for OnStar back-up battery failure, noting that DTC B1446 or B1447 may be present with a red OnStar LED. This is the most current version of this bulletin.
• PIC4541E: An earlier version of the TSB that confirms the same information across a wide range of GM vehicles.
• PIC4541A: An even earlier version of the TSB from 2007, showing the long history of this specific issue and repair procedure on GM vehicles.

Platform-Specific Known Issues

• GM Technical Service Bulletin PIC4541F explicitly covers this code on the 2013-2017 Regal. It warns technicians not to disconnect the main battery or OnStar fuse unless the ignition is off and Retained Accessory Power (RAP) has timed out, as doing so will permanently discharge the backup battery. [Bulletin #PIC4541F]

Mechanic-Grade Diagnostic Values

• Backup Battery Voltage at VCIM Connector — expected: 12.3-12.9 Volts. Failure: A voltage reading outside this range indicates a failed backup battery (BUB).
• Main System Voltage (Condition for DTC) — expected: 9.5 - 15.5 Volts. Failure: This is the normal operating voltage range for the main vehicle electrical system. The B1446 diagnostic runs when the system voltage is within this range.

Hidden / Shadow Codes Worth Checking

• B1446 03: Replace Backup Power Source Voltage Below Threshold. This is the most common symptom byte and specifically confirms the backup battery's voltage has dropped, triggering the code. (see via A professional GM-specific scan tool like a Tech 2 or GDS2 is required to view symptom bytes.)
• B1447 04: Backup Power Source Open Circuit. This code often appears alongside B1446 and indicates the VCIM sees a complete disconnection from the battery, either due to an internal failure of the battery or a wiring problem. (see via A professional GM-specific scan tool like a Tech 2 or GDS2.)

Scan Tool Commands That Help

• GDS2 / SPS: VCIM Vehicle Communication Interface Module Set-up / ONSA-OnStar Activation — This function is required when replacing the entire OnStar module (VCIM), not for a simple backup battery change. It programs the new module to the vehicle and activates it with the OnStar network.
• GDS2: Clear DTCs — After replacing the backup battery, use the 'Clear DTCs' function to erase the B1446 code from the module's memory. The red light should extinguish on the next ignition cycle.

Wiring & Ground Locations

• VCIM Connector X1 — On the Vehicle Communication Interface Module (VCIM/OnStar Module) located in the driver's side of the trunk, behind the liner.. This is the main connector for the OnStar module. The backup battery voltage can be tested at pins 13 (low reference) and 14 (supply voltage).
• G305 — A primary chassis ground point, often used for connecting the main battery negative cable to the chassis.. While not directly related to the B1446 code, ensuring a solid main battery ground at G305 is critical for overall vehicle electrical stability, which can prevent other spurious electrical issues.
• G103 — Located on the cowl in the engine compartment, typically above the brake booster.. This is a major ground point for multiple interior modules, including the Body Control Module (BCM) and Instrument Panel Cluster (IPC). A poor connection here could cause widespread communication issues, though it is not a direct cause of B1446.

Real Owner Repair Stories

• Reddit user on r/volt (2017 Chevrolet Volt) — Persistent red OnStar light for weeks. Pressing the blue button resulted in a 'call failed' message.
  ❌ Tried (didn't work) Waiting for it to resolve on its own., Disconnecting the 12V battery to reset the car (suggested but advised against)., Pulling and re-inserting the OnStar fuse (F23).
  ✅ What actually fixed it The issue was resolved by taking the vehicle to a dealer, who replaced the entire OnStar module. The repair took 2.5 hours.

OEM Part Supersession History

• 88861186 → 13509859, 13583673, 23117460 — Standard part evolution, potential improvements in battery chemistry or construction over time.
  Heads up: These part numbers are generally considered interchangeable for this application. Always verify fitment with a VIN before purchasing.