B1446 on 2014-2016 Chevrolet Impala: OnStar Backup Battery Failure Causes and Fixes

What's Unique About the 2014-2016 Chevrolet IMPALA

The 10th generation Impala, like many GM vehicles from this era, uses an integrated OnStar telematics system with a backup battery that has a finite service life of roughly 3-5 years. This battery is not rechargeable and is considered a maintenance item. The appearance of code B1446 is a predictable and well-documented issue as these vehicles age, as confirmed by GM's own Technical Service Bulletin PIC4541F, which covers the 2006-2016 Impala among many other models.

Diagnostic Flowchart

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

Generation note: This issue is not unique to the 10th generation (2014-2020) Impala. The same B1446 code and OnStar backup battery failure are common on the 9th generation (2006-2013) Impala as well, using the same part number and repair procedure.

Symptoms You May Notice

• Solid red light on the OnStar buttons (typically on the rearview mirror).
• "Service OnStar" message may appear on the Driver Information Center (DIC).
• Inability to use OnStar services or make a call by pressing the button.
• OnStar system may fail to connect when the button is pressed.
• Loss of in-vehicle WiFi hotspot functionality.

Most Likely Causes

1. OnStar Backup Battery has reached the end of its service life 🔴 High Probability → Shop Vehicle Battery The backup battery is a non-rechargeable lithium battery with a typical lifespan of 3-5 years. As the 2014-2016 Impala fleet has aged, battery failure is now a common maintenance issue. The battery is designed for a single discharge event and is not rechargeable.
   How to confirm: The presence of code B1446 (often with a symptom byte of '03' indicating voltage below threshold) is the primary confirmation. If the vehicle is more than 4 years old and has a red OnStar light, the battery is the most likely culprit.
   Typical fix: Replace the OnStar backup battery. This involves locating the OnStar module (VCIM) in the trunk, disconnecting the old battery, and installing the new one.
   Est. part cost: $40-$95

Rare But Worth Checking

• Faulty OnStar/VCIM Module: If replacing the backup battery does not clear the code, the module itself may have an internal fault. This is much less common than simple battery failure but can happen.
• Wiring or Connector Issue: Damage to the wiring harness or corrosion at the connector for the backup battery could prevent the module from seeing correct voltage, mimicking a failed battery. A diagnostic check would involve testing for voltage and resistance at the VCIM connector pins.
• Improper Service Procedure: If the main vehicle battery was recently replaced or disconnected while the ignition or Retained Accessory Power (RAP) was active, it could have triggered the OnStar backup battery to activate and fully discharge, causing it to fail prematurely. This is explicitly warned against in TSB PIC4541F.

Diagnosis Steps

1. Verify the presence of code B1446 (and possibly B1447) using an OBD-II scanner capable of reading Body (B-prefix) codes.
2. Confirm the primary symptom: a solid red OnStar indicator light on the rearview mirror.
3. Turn the ignition completely OFF. Remove the key and open the driver's door to ensure Retained Accessory Power (RAP) is deactivated. Wait at least 2-5 minutes for all vehicle systems to power down. This is a critical step to prevent damage to the new battery.
4. Locate the OnStar module (VCIM). In the 2014-2016 Impala, it is located in the trunk on the driver's side, behind the trunk liner.
5. Carefully pull back the trunk liner to access the silver Vehicle Communication Interface Module (VCIM). 🎬 See this walkthrough for accessing and replacing the VCIM module The smaller black backup battery is typically attached to a bracket on the side of the VCIM.
6. Disconnect the electrical connector for the backup battery first. Per diagnostic aids, disconnecting other VCIM harness connectors before the main X1 connector can trigger DTC B1447.
7. Unclip or unscrew the old battery from the VCIM bracket.
8. Install the new battery and reconnect its electrical connector.
9. Reassemble the trunk liner and any other trim.
10. Clear the DTCs with the scanner. Start the vehicle. The OnStar light should turn green after a short period. A current DTC will clear on its own once the VCIM detects the new battery's voltage is above the threshold, but a history code may take 50 malfunction-free ignition cycles to clear automatically. If it remains red, the code may return, indicating a deeper issue like a faulty module or wiring.

Parts You'll Likely Need

• OnStar Backup Battery (OEM #88861186) — This is the direct cause of code B1446. It is a non-rechargeable lithium battery that fails with age. Due to its hazardous material classification, shipping can be expensive.
  Trusted brands: ACDelco (GM Genuine), Ultralife
  OEM price range: $60-$95
  Aftermarket price range: $40-$70

Related Codes That Often Appear With This One

• B1447 — This code is also for the OnStar backup battery and indicates an 'Open Circuit' (symptom byte '04'). It is often set along with B1446 and points to a completely dead or disconnected battery, as noted in TSB PIC4541F.

Technical Service Bulletins (TSBs) & Recalls

• PIC4541F: Provides a diagnostic tip for OnStar back-up battery failure, which causes DTC B1446 or B1447. It warns against improper power disconnection that can drain the battery and lists dozens of affected GM models from 2006-2017.

Platform-Specific Known Issues

• GM issued Technical Service Bulletin PIC4541F, which directly addresses this issue across a wide range of GM vehicles, including the 2006-2016 Impala. It warns technicians not to disconnect the main battery or OnStar fuse while 🎬 Watch: How to locate the OnStar fuse on your Impala the ignition or Retained Accessory Power (RAP) is active, as this can activate and permanently drain the backup battery, necessitating its replacement.

Mechanic-Grade Diagnostic Values

• Backup Battery Circuit Voltage at VCIM Connector X1 — expected: Greater than 15.5 V. Failure: A reading less than 15.5 V between terminals 13 (low reference) and 14 (supply voltage) indicates a failed battery or a fault in the wiring harness between the battery and the module. Another source specifies a range of 12.3-12.9 V for a good battery on a slightly older model, but the test procedure is the same.

Hidden / Shadow Codes Worth Checking

• B1446 03: Replace Backup Power Source Voltage Below Threshold. This is the most common symptom byte and directly confirms the VCIM has determined the backup battery's voltage is too low to function. (see via GM GDS2/MDI or an equivalent professional-grade scan tool capable of reading manufacturer-specific symptom bytes.)
• B1447 04: Backup Power Source Open Circuit. This indicates the VCIM detects no voltage at all from the backup source, suggesting a completely dead battery, an internal open in the battery pack, or a disconnected plug. (see via GM GDS2/MDI or an equivalent professional-grade scan tool.)

Scan Tool Commands That Help

• GM GDS2: Clear DTCs — This is used after the physical replacement of the backup battery to clear the B1446 code. While the current code should clear on its own after the new battery is detected, using the scan tool provides immediate confirmation of the fix.
• GM SPS (Service Programming System): VCIM Vehicle Communication Interface Module Set-up / OnStar Activation — This function is NOT required for a simple backup battery replacement. It is only used when the entire VCIM (the silver OnStar module itself) is replaced with a new unit.

Wiring & Ground Locations

• VCIM Connector X1 — The main electrical harness connector at the Vehicle Communication Interface Module (VCIM), located in the trunk behind the driver's side liner.. This connector contains the pins for the backup battery circuit. Specifically, Pin 14 is the battery supply voltage and Pin 13 is the low reference (ground). Testing between these two pins verifies the battery's output and the integrity of its immediate wiring.
• VCIM Ground — The wiring diagram for the 2014 Impala Limited indicates the Vehicle Communication Interface Module (VCIM) shares a ground point with the right tail lamp and trunk relay.. While a bad ground is a very unlikely cause for this specific code (which points to battery voltage, not module function), a loose or corroded ground could theoretically cause erratic behavior from the VCIM. This is a secondary check if a new battery and wiring tests don't resolve the issue.

OEM Part Supersession History

• 19118855, 22704633, 42454411 → 88861186 — Standard part consolidation and updates by the manufacturer over time.
  Heads up: All listed part numbers are interchangeable and have been replaced by the current GM Genuine part number 88861186. There are no known incompatibilities between these versions.