B1447 on 2014-2016 Chevrolet Impala: OnStar Backup Battery Failure Guide

What's Unique About the 2014-2016 Chevrolet IMPALA

The tenth-generation Impala (2014-2020) uses a common GM OnStar module where the internal lithium backup battery has a finite service life of roughly 5-7 years. As these vehicles have aged, this failure has become a predictable maintenance item. The issue is so common that GM has issued Technical Service Bulletins, like #PIC4541F (and its subsequent revisions), that cover a wide range of vehicles, including the Impala, all pointing to this same failure mode and repair procedure.

Diagnostic Flowchart

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

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).
• OnStar system is non-functional or unable to connect to an advisor.
• Audible voice prompt from OnStar stating a system issue upon vehicle startup (less common).

Most Likely Causes

1. Failed OnStar Backup Battery 🔴 High Probability The internal lithium battery is a non-rechargeable component with a natural chemical lifespan. Failure after 5-7 years is normal and expected across many GM models using this OnStar module. The battery is designed to be a service item, though it is not part of routine scheduled maintenance.
   How to confirm: The presence of code B1447 combined with a red OnStar LED is a definitive indicator. A scan tool that can read Body (B) codes is required to see the code. Given the extremely high failure rate, visual confirmation and the presence of the code are sufficient for diagnosis without further electrical testing.
   Typical fix: Replace the OnStar backup battery module. On the 2014-2016 Impala, the OnStar module (VCIM) is typically located in the trunk, behind the driver's side liner. The small battery module is attached to it.
   Est. part cost: $40-$70

Rare But Worth Checking

• Wiring Harness Damage:
• Faulty VCIM/OnStar Module:

Diagnosis Steps

1. Verify the primary symptom: a solid red light on the OnStar unit in the rearview mirror.
2. Use a capable OBD-II scanner to read codes from the Body Control Module (BCM) or Telematics module. Confirm that code B1447 is present.
3. IMPORTANT: Before proceeding with any repair, turn the ignition completely OFF. Remove the key and open and close the driver's door to ensure Retained Accessory Power (RAP) is deactivated. This step is critical. Disconnecting power while the system is active can permanently destroy the new backup battery upon installation.
4. Open the trunk and locate the OnStar module (VCIM). It is a silver metal box typically found on the driver's side, behind the carpeted trunk liner. 🎬 Watch: See how to access and replace the backup battery. You may need to remove plastic sill plates or clips to pull the liner back.
5. The backup battery is a small black box attached to the side of the larger silver OnStar module, often held in a simple bracket.
6. Carefully disconnect the single electrical connector from the backup battery module.
7. Remove the old battery from its bracket. It may be held by a clip or small screw.
8. Install the new backup battery, reconnect the electrical connector, and secure it in the bracket.
9. Use the scan tool to clear the B1447 trouble code. The code may also clear on its own after approximately 50 malfunction-free ignition cycles, but clearing it with a scanner is immediate.
10. Turn the ignition to 'ON' and wait a minute. Verify the OnStar indicator light is now green, indicating a successful repair.

Parts You'll Likely Need

• OnStar Backup Battery (OEM #88861186) — This is the direct cause of the B1447 code. It is a non-rechargeable battery that fails due to age. The original part is often an Ultralife brand battery.
  Trusted brands: ACDelco, GM Genuine, Dorman, Ultralife
  OEM price range: $50-$70
  Aftermarket price range: $40-$60

Related Codes That Often Appear With This One

• B1446 — B1446 indicates the backup battery's voltage is low, while B1447 indicates a complete open circuit (no voltage). Both codes point to a failed backup battery and are often mentioned together in GM service literature as definitive signs of battery failure.

Technical Service Bulletins (TSBs) & Recalls

• PIC4541F / PIC4541G: Provides diagnostic tips for OnStar back-up battery failure, indicated by DTC B1446 or B1447 and a red OnStar LED. It covers a vast range of GM models, including the 2014-2016 Impala.
• PIT5463B: A related bulletin for older models that also discusses a red LED and code B1447 after certain OnStar upgrades, reinforcing the fix is to install a new backup battery.

Platform-Specific Known Issues

• GM Technical Service Bulletin #PIC4541F (and later versions like PIC4541G) directly addresses this issue, noting that DTC B1446 or B1447 with a red OnStar LED indicates a backup battery failure. It specifically warns technicians to never disconnect the main vehicle battery or OnStar fuse unless the ignition is OFF and Retained Accessory Power (RAP) has timed out, as doing so can permanently destroy the backup battery.
• On the 10th Gen Impala, accessing the module requires pulling back the trunk liner on the driver's side. No special tools are needed, but care should be taken not to break the plastic trim clips that hold the liner in place.

Mechanic-Grade Diagnostic Values

• OnStar Backup Battery Voltage — expected: A new battery will have an open-circuit voltage of approximately 3.0V - 3.6V. The VCIM module, however, diagnoses the battery based on internal resistance under a load test, not just open-circuit voltage.. Failure: The B1447 04 code sets when the module detects an open or high-resistance circuit, meaning it cannot draw power from the battery. This is more indicative of a complete internal failure than a low voltage reading (which would set B1446).

Hidden / Shadow Codes Worth Checking

• B1447 04: Backup Power Source Open Circuit. This is the most common and specific sub-code for this failure, indicating the VCIM sees a complete lack of connection to the backup battery. (see via A professional GM-specific scan tool, such as a Tech 2 or a modern laptop running GDS2 software, is required to view symptom bytes.)

Scan Tool Commands That Help

• GDS2 (Global Diagnostic System 2): Module Diagnostics > K74 Telematics Communication Interface Control Module > On-Board Diagnostic Check — This function commands the VCIM to perform a self-test of its systems, including the backup battery circuit. A failure reported here after running the test confirms a fault within the OnStar system, and if B1447 is present, it points directly to the battery or its immediate wiring.
• GDS2 (Global Diagnostic System 2): Clear All DTCs — After replacing the backup battery, this command should be used to immediately clear the B1447 code and extinguish the red OnStar light. While the code may clear on its own after 50 good ignition cycles, this provides immediate confirmation of a successful repair.

Wiring & Ground Locations

• K74 Telematics Communication Interface Control Module Connector — On the main silver OnStar/VCIM module, located behind the driver's side trunk liner.. This is where the backup battery connects. Pin 1 (typically a Yellow/Violet wire) is the Battery Positive Voltage from the backup battery. Pin 2 (typically a Black wire) is the ground reference. Testing for continuity between the battery connector and these pins can rule out a wiring issue.
• G402 or similar trunk ground — In the rear of the trunk area, often on the floor or near a wheel well. Multiple circuits ground at this point.. The ground circuit for the VCIM (and by extension, the backup battery) ultimately terminates at a chassis ground point like this. While a failure here is very rare and would likely cause many other issues, it is the final point in the ground side of the circuit.

Real Owner Repair Stories

• Reddit user in r/MechanicAdvice (2015 Chevrolet Impala) — Multiple electrical issues including a persistent "Service Side Detection System" message, which is a common symptom of network communication issues that can sometimes be triggered by modules with low power, like an OnStar module with a failing backup battery.
  ❌ Tried (didn't work) Took it to a dealer who wanted to replace the entire wiring harness., Visited four different mechanics with no resolution., Inspected the side detection module in the rear bumper and found no issues.
  ✅ What actually fixed it While the original poster's final fix for all issues isn't detailed, the thread highlights a common diagnostic dead-end where complex wiring issues are suspected for communication faults, when a simple module power issue (like the B1447 fault) can be a contributing factor or a separate, easily-solvable problem. The user's description of widespread electrical gremlins is common when a module on the data bus has power issues.

OEM Part Supersession History

• 19118855, 22704633, 42454411 → 88861186 — Standard part number consolidation and minor revisions over time.
• 88861186 → 84544335 (for different models) — Part for newer generation OnStar systems (Gen 10.x and later).
  Heads up: The part 84544335 is NOT compatible with the 2014-2016 Impala. It has a different physical connector and is intended for newer GM vehicles. Using it will not resolve the B1447 code on this platform.