B3928 on 2019-2020 Buick Envision: Causes for 'No FOB Detected' and Fixes

What's Unique About the 2019-2020 Buick ENVISION

What's unique to this Buick and other GM platforms of the era is that code B3928 is rarely about a single failed antenna. Instead, it's a symptom of a larger, documented problem. GM issued Technical Service Bulletin (TSB) 23-NA-163, which identifies that low voltage events (like a battery change or jump-start) can corrupt the memory of specific 'GEN3R' BCMs, causing them to falsely report failures on multiple keyless entry antenna circuits. This means the solution is a targeted software reprogram, not hardware replacement, a fact explicitly stated in the TSB to prevent unnecessary, costly repairs.

Diagnostic Flowchart

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

Symptoms You May Notice

• Vehicle will not crank or start
• Engine starts and immediately stalls
• "No FOB Detected" or "Key FOB Not Detected" message on the dash
• Key fob buttons (lock/unlock/remote start) are inoperative
• Security light may be flashing
• Multiple seemingly unrelated electrical issues.

Most Likely Causes

1. Body Control Module (BCM) Memory Corruption 🔴 High Probability → Shop Body Control Module As documented in GM TSB 23-NA-163, certain BCMs (specifically 'GEN3R' models) are susceptible to memory corruption following a low-voltage event like a battery replacement, jump-start, or even just a battery disconnect/reconnect.
   How to confirm: A professional technician will use a GM-specific scan tool (GDS2) to verify that B3928 is present with at least two other codes from the B3924-B3927 range, and often with a primary code B389A. They will then confirm the BCM is a 'GEN3R' part number by navigating to Module Diagnostics > [K9] Body Control Module > Identification Information. If the part number is on the TSB's eligible list, the diagnosis is confirmed.
   Typical fix: The BCM must be reprogrammed by a dealer or qualified independent shop using the specific software procedure outlined in TSB 23-NA-163. This is a software flash, not a parts replacement. The specific SPS function is named "Programming A Per Bulletin 23-NA-163 and 23-NA-165 Only".
   Est. part cost: $0

Rare But Worth Checking

• Failed Keyless Entry Antenna: → Shop Antenna While this is what the code technically refers to, it is a very rare cause for this specific problem on this vehicle. This should only be investigated if the BCM reprogramming from TSB 23-NA-163 fails to resolve the issue and B3928 is the *only* code present.
• Weak or Dead Key Fob Battery: → Shop Vehicle Battery This can cause a 'No FOB Detected' message but will not typically set the B3928 fault code. It's an easy first step to try replacing the fob battery before pursuing professional diagnosis. If the battery is dead, the vehicle can often be started by placing the fob in a designated transmitter pocket, usually in the center console.
🎬 See how to start your Buick with a dead fob.

Diagnosis Steps

1. Confirm the primary symptoms: No Crank/No Start, No Fob Detected.
2. Scan the Body Control Module (BCM) for codes using a professional-grade scanner like GM's GDS2.
3. Verify if B3928 is present along with two or more other codes from the B3924-B3927 range. Note if B389A is also present.
4. If multiple codes are present, consult TSB #23-NA-163. The bulletin explicitly warns *not* to replace modules before performing the software update.
5. Using the GDS2 scan tool, navigate to 'Module Diagnostics' > '[K9] Body Control Module' > 'Identification Information' to view the 'Base Model Part Number'.
6. Confirm the BCM part number is on the list of eligible 'GEN3R' modules. Eligible part numbers include 13518569, 13518570, 13518602, 13519619, 13527252, 13527260, 13533809, and others listed in the TSB.
7. If confirmed, follow the specific BCM reprogramming procedure detailed in TSB #23-NA-163 using GM's Service Programming System (SPS). This involves selecting 'K9 Body Control Module' and then 'Programming A Per Bulletin 23-NA-163 and 23-NA-165 Only'.
8. After reprogramming, perform the 'Body Control Module IMMO Learn with Existing Transponder or Remote Key' procedure.
9. Clear all codes and verify that the vehicle starts and all key fob functions are restored.

Parts You'll Likely Need

• No parts typically needed — The most common cause is a software issue that is resolved by reprogramming the existing Body Control Module (BCM), as per TSB 23-NA-163.
  OEM price range: $0
  Aftermarket price range: $0
• GEN3R Body Control Module (BCM) - Only if reprogramming fails (OEM #13533809, 13533813, 13533814, 13533817, 13533821, etc. (verify by VIN)) — In the rare event the BCM has a hardware failure and cannot be reprogrammed, it would need replacement. 🎬 Watch: How to replace a GM BCM and perform relearn. The TSB lists numerous eligible part numbers.
  Trusted brands: ACDelco (OEM)
  OEM price range: $300 - $600
  Aftermarket price range: $150 - $350

Related Codes That Often Appear With This One

• B389A — This is often the primary fault code that triggers the B392x environmental codes due to the BCM memory corruption. The TSB notes that if this code isn't present, a technician should disconnect and reconnect the battery for 30 seconds to see if it appears.
• B3924, B3925, B3926, B3927 — The BCM software issue causes it to falsely report faults on multiple keyless entry antenna circuits simultaneously. The presence of three or more of these codes along with B389A is a key indicator of the TSB condition.

Technical Service Bulletins (TSBs) & Recalls

• 23-NA-163: Addresses a No Crank, No Start, No FOB Detected condition caused by BCM memory corruption, and provides a specific reprogramming procedure as the fix. It explicitly warns against replacing parts before performing the software update.

Platform-Specific Known Issues

• A known issue documented in GM TSB #23-NA-163 describes a BCM memory corruption event after a low voltage situation (e.g., battery replacement, jump-start). This is the primary cause for this group of codes on the 2019-2020 Envision and its platform mates.
• The issue is specific to vehicles equipped with a 'GEN3R' Body Control Module, which can be identified by its part number using a GM scan tool.

Mechanic-Grade Diagnostic Values

• Keyless Entry Antenna Signal Circuit Voltage — expected: Less than 1.0 V. Failure: A reading of 1.0 V or greater indicates a short to voltage in the circuit.
• Keyless Entry Antenna Activation Voltage (using DMM MIN/MAX) — expected: Greater than 1.0 V (captured max voltage). Failure: If the max voltage captured does not exceed 1.0 V when activating the antenna (e.g., pressing door handle button), it points to a fault in the antenna or its circuit.

Hidden / Shadow Codes Worth Checking

• B3928 00: The '00' is a symptom byte meaning 'No Additional Symptom Information'. The presence of this specific code is a key criterion listed in TSB #23-NA-163 to confirm the BCM memory corruption has occurred. (see via GM GDS2 or equivalent professional scan tool.)
• B389A 00: This code for 'Environment Identification' with the '00' symptom byte is often the primary fault that confirms the BCM memory corruption event, triggering the other B392x codes. (see via GM GDS2 or equivalent professional scan tool. The TSB advises that if this code is not present, disconnecting the battery for 30 seconds may cause it to set.)

Scan Tool Commands That Help

• GDS2 / SPS: Programming A Per Bulletin 23-NA-163 and 23-NA-165 Only — This is the primary and required software fix when B3928 is present with other B392x codes due to BCM memory corruption as per the TSB.
• GDS2: Module Diagnostics > Remote Control Door Lock Receiver > Configure/Reset Functions > Add or Replace Key Fobs — This function is used to manually program new or existing key fobs to the vehicle after a BCM replacement or if they lose programming for other reasons.
• GDS2: Body Control Module IMMO Learn with Existing Transponder or Remote Key — This procedure is required after the TSB reprogramming to re-learn the existing keys to the immobilizer system.

Wiring & Ground Locations

• K9 Body Control Module (BCM) — Located in the center console, directly behind the lower trim panel on the passenger side of the vehicle.. This is the module that stores key fob data and controls the keyless entry system. The software corruption occurs within this module. Physical access is needed for replacement or checking connections.
• G103 — Located at the left rear of the engine compartment on the cowl, above the brake booster.. This is a primary ground point for the BCM and the Remote Control Door Lock Receiver. A poor connection at G103 can cause intermittent low voltage to the BCM, potentially triggering the memory corruption event that leads to code B3928.
• BCM Connector X4 — One of the seven connectors on the BCM, located on the passenger side of the center console.. This connector contains multiple battery positive voltage input pins (e.g., Pins 1, 2, 3, 4, 5). Verifying stable voltage at these pins is a key step if a BCM hardware failure is suspected.

Real Owner Repair Stories

• WAMS Performance Customer Review (2020 Chevrolet Silverado (platform mate)) — Vehicle was dead, no-start, no remote function.
  ❌ Tried (didn't work) Jump start (which caused the BCM to fail)
  ✅ What actually fixed it The factory BCM had failed completely during a jump start. Replacing the BCM with a new, pre-programmed unit brought the truck 'back to life immediately' with all functions restored. This represents a true hardware failure, not a software glitch.
• WAMS Performance Customer Review (2020 GMC Yukon Denali (platform mate)) — Intermittent 'service trailer brake system' messages and random vehicle shutoffs.
  ❌ Tried (didn't work) Initial diagnosis was unclear.
  ✅ What actually fixed it The BCM was failing internally. A replacement BCM resolved all intermittent electrical issues. This highlights that BCM failure can manifest in various ways beyond just the keyless entry system.

When the Usual Fixes Don't Work

• While TSB #23-NA-163 correctly identifies a BCM software reprogram as the fix in the vast majority of cases, it is critical to recognize that the low-voltage event (like a jump-start) that triggers the software corruption can sometimes cause a catastrophic hardware failure within the BCM itself. In these edge cases, documented on platform-mate vehicles like the Chevrolet Silverado, the BCM will not respond to reprogramming and must be physically replaced. Therefore, if the specific SPS reprogramming function fails or does not resolve the symptoms, a BCM hardware failure should be considered the primary diagnosis, rather than attempting the reprogram multiple times.

OEM Part Supersession History

• 13592452 → 13545326 — Part revision by manufacturer.
  Heads up: These are for the keyless entry antenna, used only in the rare case of actual antenna failure.
• 13592451 → 13546098 — Part revision by manufacturer.
  Heads up: These are for the keyless entry antenna, used only in the rare case of actual antenna failure.
• Varies (e.g., 13518569, 13527252) → Varies (Latest P/N provided by dealer) — GM regularly updates BCM hardware and software.
  Heads up: When replacing a BCM, the specific part number is less important than ordering by VIN. The dealer or a specialized supplier will provide the latest compatible, superseded part number for the vehicle's specific configuration.

Model Year Variations Within This Range

• 2019-2020: While the 2019 model received a minor facelift and a new 9-speed transmission for the optional 2.0L turbo engine, there are no documented differences in the BCM, keyless entry system, or wiring that would affect the diagnosis or repair of code B3928 between these two model years. Both are subject to TSB 23-NA-163.