B1000 on 2013-2017 Buick LaCrosse: OnStar Module Failure Causes and Fixes

What's Unique About the 2013-2017 Buick LACROSSE

While B1000 can be a vague code on many cars, its meaning on this specific LaCrosse platform—and indeed across dozens of GM models from this era—is well-documented by GM. The manufacturer issued multiple service bulletins (PIC3278F and PIC3278G) explicitly identifying the OnStar module as the culprit when this code appears, often alongside a U1500 communication code. This isn't a random electrical gremlin; it's a known, widespread failure point of a specific component, making diagnosis much more direct than on other vehicles where B1000 could mean any number of things.

Diagnostic Flowchart

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

Generation note: This range covers two LaCrosse generations: the end of the second (2013-2016) and the start of the third (2017). While the TSBs apply to both, the specific OnStar module part number and its location may differ. The fundamental problem and the required fix (module replacement and programming) are the same for both generations.

Symptoms You May Notice

• "Phone Unavailable" audio message when starting the car or pressing an OnStar button.
• Red or unlit status light on the OnStar buttons in the rearview mirror.
• OnStar buttons (blue, red) are completely unresponsive.
• Inability to use any OnStar services or connect to the MyBuick mobile app for remote start, lock, or location services.
• Potential for a parasitic battery drain, causing a dead battery if the vehicle sits for an extended period.
🎬 See how to test for a parasitic battery drain.

Most Likely Causes

1. Internal Failure of the OnStar Module (VCIM) 🔴 High Probability This is a well-documented failure specified in GM Technical Service Bulletins #PIC3278G and #PIC3278F. The internal electronics of the module fail over time, causing it to fail its self-test and set the B1000 code. This is a widespread issue affecting many GM models of the era.
   How to confirm: Use a professional scan tool to confirm the B1000 code is being set by the 'Telematics Communication Interface Module'. The presence of the 'Phone Unavailable' audio message is also a strong indicator. The module is often located behind the glove box or in the driver's side of the trunk, behind the trim.
   Typical fix: Replace the OnStar/VCIM module and have the new unit professionally programmed to the vehicle's VIN. Some owners report parts being on backorder.
   Est. part cost: $250-$550

Rare But Worth Checking

• Wiring or Connector Issue at the VCIM: While the code points to an internal fault, it's always possible that a corroded connector or damaged wire is causing a power, ground, or communication issue that mimics a module failure. A visual inspection of the module's harness is a wise, though less common, diagnostic step.
• Low Vehicle Voltage: In rare cases, a dying battery or an improper jump-start can cause a voltage spike or drop that sets a false B1000 code in a module's memory. Before replacing parts, ensure the battery is healthy, clear the codes, and see if the B1000 returns.

Diagnosis Steps

1. Confirm the primary symptom: Listen for the 'Phone Unavailable' audio message upon startup.
2. Check the OnStar status light on the rearview mirror. A red or off light indicates a problem.
3. Connect a professional-grade scan tool capable of reading manufacturer-specific Body (B) and Communication (U) codes.
4. Scan all modules for codes. Confirm that the B1000 code is present and being reported by the Telematics Communication Interface Module (VCIM).
5. If confirmed, locate the VCIM. It is typically located behind the glove box assembly or in the driver's side rear trunk area, behind the trim panel. Consult a service manual for the exact location for your model year.
6. Before replacement, it is best practice to inspect the wiring and connector at the VCIM for any visible damage or corrosion.
7. Replace the VCIM.
8. Perform the mandatory Service Programming System (SPS) procedure to program the new module to the vehicle's VIN and configuration.

Parts You'll Likely Need

• OnStar/Telematics Communication Interface Module (VCIM) (OEM #Varies by year and options. Possible numbers include 22903686 (2013), 23127633 (2014), 20827036. Part numbers are frequently superseded. ALWAYS verify the correct part number with a dealer using the vehicle's VIN before purchasing.) — This module is the direct cause of the B1000 code and 'Phone Unavailable' symptom as identified by GM's own service bulletins.
  Trusted brands: GM Genuine Parts, ACDelco
  OEM price range: $400-$550
  Aftermarket price range: $250-$400 (Used/Remanufactured)

Related Codes That Often Appear With This One

• U1500 — This is a LIN Bus communication code. The TSBs specifically mention that the internal OnStar module fault can set either B1000 or U1500, and they often appear together.

Technical Service Bulletins (TSBs) & Recalls

• PIC3278G: States that an internal fault in the OnStar module can produce a 'Phone Unavailable' audio message and set a B1000 or U1500 code.
• PIC3278F: An earlier version of the same bulletin with the same information, confirming this has been a known issue for some time.

Platform-Specific Known Issues

• GM Customer Satisfaction Program #17398 was issued for some 2008-2016 LaCrosse models regarding replacement OnStar modules that may have been improperly programmed during a prior service visit, rendering them non-functional.
• This failure is extremely common across the GM lineup from this era, often occurring just after the 3-year/36,000-mile bumper-to-bumper warranty expires.
• Owners in forums have reported that replacement modules can sometimes be on backorder from GM, leading to extended repair times.

Mechanic-Grade Diagnostic Values

• Parasitic Battery Drain (Current Draw) — expected: Under 50mA after the vehicle has entered sleep mode (typically 7-12mA).. Failure: A sustained draw near 380mA (0.38A) that drops to normal levels when the OnStar/VCIM fuse is pulled strongly indicates a faulty module.
• High-Speed GMLAN Network Resistance — expected: Approximately 60 Ω when measured between Pin 6 and Pin 14 of the Data Link Connector (DLC).. Failure: A reading of 120 Ω indicates an open circuit in the network or a missing terminating resistor, which could be internal to a module like the VCIM.

Hidden / Shadow Codes Worth Checking

• B1000 00: ECU Performance - A generic confirmation that the module detected an internal malfunction with no subtype. 🎬 Watch this short explanation of the Buick B1000-00 code. (see via GM GDS2 diagnostic platform)
• B1000 04: ECU RAM Failure - Indicates a failure of the module's Random Access Memory. (see via Professional scan tool like GM GDS2 or Tech2)
• B1000 39: ECU Performance Internal Electronic Failure - A general hardware failure inside the module. (see via Professional scan tool like GM GDS2 or Tech2)
• B1000 3B: ECU Performance Internal Self Test Failed - The module failed its own power-on self-test. (see via Professional scan tool like GM GDS2 or Tech2)
• B1000 43: Special Memory Failure - The control module is indicating a memory failure of an undefined type. (see via Professional scan tool like GM GDS2 or Tech2)

Scan Tool Commands That Help

• GM GDS2 (Global Diagnostic System 2): K73 Telematics Communication Interface Control Module: Programming and Setup — This specific function, part of the Service Programming System (SPS), is mandatory after installing a new VCIM. It downloads the correct software and VIN to the new module, enabling it to communicate with the vehicle and the OnStar network.
• GM GDS2 / Tech2: Module ID Information / Module 2 Information — Before replacing the module, this function should be used to read and record the old module's identification numbers. This can be required by GM's Technical Assistance Center (TAC) to authorize and order the correct restricted replacement part.

Wiring & Ground Locations

• VCIM Module Location (2013-2014) — For the 2013 and 2014 LaCrosse, the VCIM is typically mounted in the trunk.. Correctly locating the module is the first step for visual inspection of its connector and for replacement.
• G302 / G303 (Reference) — On similar GM sedans, grounds like G302 and G303 are located in the door sills or under/near the rear seat. The exact location for a 2013-2017 LaCrosse should be verified with a service manual.. A poor ground connection to the VCIM can cause communication errors or a no-power condition that could be misdiagnosed as an internal module failure. Checking major body grounds in the vicinity of the module is a valid diagnostic step.

OEM Part Supersession History

• 22903686 → 23127633 — Standard part revision and update by manufacturer.
  Heads up: Part number 23127633 is now also listed as discontinued. It is critical to verify the latest correct part number with a GM dealer using the VIN. WARNING: Used modules are VIN-locked to the donor vehicle. A GM dealer's SPS software cannot reprogram a used module, which will render OnStar services non-functional.

Model Year Variations Within This Range

• 2013-2017: The diagnostic software platform changed. Models from 2013/2014 onward require the Global Diagnostic System 2 (GDS2) software, whereas earlier models may have used the Tech2Win simulator. A technician must use the correct software for the specific model year being serviced.
• 2013-2016 vs 2017: The 2017 model year marks the beginning of the third-generation LaCrosse. While the OnStar failure is common to both, the physical part number and mounting location of the VCIM may be different from the second-generation (2013-2016) models. Always verify parts by VIN.