B3928 on 2018-2025 Cadillac XT5: 'No FOB Detected' Causes and Fixes

What's Unique About the 2018-2025 Cadillac XT5

The Cadillac XT5, along with many other GM vehicles of this era, uses a specific Body Control Module known as the 'GEN3R' BCM. This module is susceptible to a memory corruption event following a low-voltage situation, such as a battery replacement, jump-start, or even just charging a weak battery. GM has acknowledged this widespread issue with Technical Service Bulletin #23-NA-163, which details a specific software-based repair procedure. The key takeaway is that the problem is almost always software-related, not a hardware failure of the antenna or BCM itself. The TSB explicitly warns technicians *not* to replace modules before performing the software procedure.

Diagnostic Flowchart

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

Generation note: The 2018-2025 year range covers the first generation of the Cadillac XT5 (2017-present). The issue described in TSB #23-NA-163 was updated in August 2024 to explicitly include the Cadillac XT5, among other models, confirming its relevance to this platform.

Symptoms You May Notice

• "No FOB Detected" or "No Remote Detected" message on the driver information center.
🎬 Watch: How to start your XT5 when no remote is detected.
• Vehicle will not crank or start.
• Engine starts and immediately stalls.
• Key fobs are inoperative for both passive entry (door handles) and active button functions (lock/unlock/remote start).

Most Likely Causes

1. Body Control Module (BCM) Memory Corruption 🔴 High Probability The GEN3R BCM used in these vehicles can lose its key fob and environment memory after a low-voltage event like a battery change, jump-start, or from a weak battery. This is a known design susceptibility acknowledged by GM.
   How to confirm: A professional scan tool will show code B3928 along with several other antenna codes (B3924-B3927) and, crucially, B389A ('Environment Identification'), all with a '00' symptom byte. The presence of multiple antenna codes simultaneously makes a BCM software issue far more likely than multiple hardware failures. The TSB instructs technicians to check for B389A, and if it's not present, to disconnect/reconnect the battery for 30 seconds to see if it appears.
   Typical fix: Perform the specific BCM reprogramming and immobilizer relearn procedure as detailed in TSB #23-NA-163. This is a software-only fix and does not involve replacing parts. The TSB outlines two procedures, 'Programming A' and 'Programming B', depending on if a standard relearn was already attempted.
   Est. part cost: $0

Rare But Worth Checking

• Faulty Key Fob Battery: Always try this first. 🎬 See this quick walkthrough for replacing your key fob battery. A weak fob battery can cause a 'No FOB Detected' message. If the car starts by placing the fob in the transmitter pocket (in the center console cupholder), the CR2032 fob battery is the most likely culprit. This is a separate issue from the BCM glitch and would not typically set a group of B-codes.
• Failed Keyless Entry Antenna: While the code technically points to an antenna circuit, it's rare for one to fail. This would typically set only the single B3928 code, not the entire group of antenna codes (B3924-B3928). If only B3928 is present, the antenna itself or its wiring may be at fault.
• Wiring Issue or Poor Ground: A loose or corroded ground connection for the BCM could create an intermittent low-voltage condition, triggering the memory corruption. Based on GM's ground numbering convention, a technician would inspect G2xx-series grounds located in the front passenger compartment. This is less common than a simple battery event but worth investigating if the problem recurs after the TSB procedure has been performed.

Diagnosis Steps

1. Attempt to start the vehicle by placing the key fob in the transmitter pocket located in the center console cupholder. 🎬 Learn how to unlock and start your car with a dead fob. If it starts, replace the CR2032 battery in the key fob.
2. If the vehicle still does not start, connect a professional-grade scan tool capable of reading Body (B) codes, such as the GM GDS2.
3. Check for codes B3924, B3925, B3926, B3927, and B3928 in the Body Control Module (K9). Note if code B389A is also present, and confirm they all have a '00' symptom byte, as this is the key indicator for the TSB procedure.
4. If multiple antenna codes and B389A 00 are present, do not replace any parts. The vehicle must be taken to a GM dealership or a qualified independent shop with access to GM's online Service Programming System (SPS).
5. The technician must identify the BCM as a 'GEN3R' type by checking the part number in GDS2 and follow the specific reprogramming and immobilizer relearn procedure outlined in TSB #23-NA-163.
6. Confirm that the vehicle starts and all key fob functions (passive and active) work correctly with all fobs after the procedure is complete.

Parts You'll Likely Need

• No parts typically required — The most common cause is a software glitch that requires reprogramming, not hardware replacement. TSB #23-NA-163 allocates 0.5 hours of labor for the software procedure under warranty.
  OEM price range: $0
  Aftermarket price range: $0
• Key Fob Battery (OEM #CR2032) — A simple and inexpensive first step to rule out a weak fob battery as the cause of 'No FOB Detected' messages. This should be tried before any professional diagnosis.
  Trusted brands: Energizer, Duracell, Panasonic
  OEM price range: $5-$10
  Aftermarket price range: $2-$5

Related Codes That Often Appear With This One

• B3924, B3925, B3926, B3927 — These are sibling codes for the other keyless entry antennas. When they appear together with a '00' symptom byte, it confirms a system-wide fault, almost certainly the BCM memory corruption issue described in TSB #23-NA-163.
• B389A — This code for 'Environment Identification' is often the primary DTC that points directly to the BCM memory corruption issue when seen with the antenna codes. The TSB specifically mentions looking for this code with a '00' symptom byte as a key indicator.
• P0513 — A related TSB (#23-NA-165) mentions this code for 'Invalid Immobilizer Key' can appear with similar symptoms. It points to a similar BCM memory corruption issue.

Technical Service Bulletins (TSBs) & Recalls

• 23-NA-163: Addresses a No Crank/No Start condition with codes B3924-B3928 and B389A set, caused by BCM memory corruption after a low-voltage event. The fix is a specific reprogramming procedure. This TSB has been updated multiple times, with the Cadillac XT5 being officially added in an August 2024 revision.

Platform-Specific Known Issues

• The GEN3R Body Control Module in the 2018-2025 XT5 is known to be susceptible to memory corruption after low-voltage events, as documented in GM TSB #23-NA-163.
• An August 2024 revision to TSB #23-NA-163 specifically added the Cadillac XT5 and XT6, confirming this is a recognized issue for these models.

Hidden / Shadow Codes Worth Checking

• B3928 00: The '00' is a symptom byte indicating 'No Additional Symptom Information'. TSB #23-NA-163 specifically requires this symptom byte to be present for B3928 and its companion codes (B3924-B3927) to confirm the BCM reprogram is the correct procedure. (see via GM GDS2 or an equivalent professional scan tool that can read manufacturer-specific symptom bytes.)
• B389A 00: This code for 'Environment Identification' with the '00' symptom byte is the primary indicator of the BCM memory corruption event. The TSB directs technicians to look for this code specifically. (see via GM GDS2 or an equivalent professional scan tool.)

Scan Tool Commands That Help

• GM SPS (Service Programming System): K9 Body Control Module - 'Programming A Per Bulletin 23-NA-163 and 23-NA-165 Only' — This is the initial software procedure to fix the BCM memory corruption, used when an immobilizer learn has NOT been attempted yet.
• GM SPS (Service Programming System): K9 Body Control Module - 'Programming B Per Bulletin 23-NA-163 Only' — This is the secondary software procedure, used only if 'Programming A' and a standard immobilizer learn were already attempted but failed to resolve the issue.
• GM SPS (Service Programming System): Immobilizer procedure - 'Body Control Module IMMO Learn with Existing Transponder or Remote Key' — This relearn procedure is performed immediately after running 'Programming A' to re-link the existing key fobs to the newly programmed BCM.
• GM GDS2: Module Diagnostics > [K9] Body Control Module > Identification Information — This function is used to view the BCM's Base Model Part Number (BMPN) to verify it is a 'GEN3R' type and is on the list of eligible part numbers before attempting the TSB procedure.

Wiring & Ground Locations

• K9 — The Body Control Module (BCM) is located in the passenger compartment, typically under the dashboard.. This is the module that stores the key fob data and suffers from the memory corruption detailed in TSB #23-NA-163. All diagnostic codes (B3928, B389A, etc.) are read from this module.
• Keyless Entry Antennas — There are multiple antennas. Locations include the center console, rear compartment/floor, and rear body area.. While rarely the cause, in a case where only a single code like B3928 is present, a technician may need to access a specific antenna or its wiring for inspection.
• G2xx Grounds — General location for ground points within the front passenger compartment (dashboard/front seats area).. A loose or corroded ground in this area could cause an intermittent low-voltage supply to the BCM, triggering the memory corruption that leads to code B3928. This is a rare but plausible root cause if the issue reoccurs after reprogramming.

Real Owner Repair Stories

• Reddit user in r/Cadillac (2017 Cadillac XT5) — Intermittent 'No Remote Detected' message, vehicle would not start or sometimes shut off. Could not lock/unlock doors. The issue happened frequently during a night of pizza delivery involving many stops and starts.
  ❌ Tried (didn't work) Replacing the key fob battery worked for a couple of weeks, but the problem returned.
  ✅ What actually fixed it The user was able to get the car started by placing the fob in the center console pocket. The final resolution was not posted, but the story is a perfect example of the symptoms and the temporary success of the backup starting procedure.
• Reddit user in r/Cadillac (2018 Cadillac XT5) — The user was trying to program a second key fob, but the procedure failed.
  ❌ Tried (didn't work) The dealership attempted the standard key programming procedure. They then tried to program a brand new key, but claimed the new key was 'bricked' (rendered inoperable).
  ✅ What actually fixed it The dealership's diagnostics led them to conclude the Body Control Module (BCM) itself was faulty and needed to be replaced. This serves as a valuable counter-example where the software-only TSB procedure was deemed insufficient and a hardware replacement was required.

OEM Part Supersession History

• Multiple (see list) → N/A — These are the specific Base Model Part Numbers (BMPNs) for the GEN3R BCM that are known to be affected by the memory corruption issue and are eligible for the TSB #23-NA-163 reprogramming fix.
  Heads up: Eligible Part Numbers: 13518569, 13518570, 13518602, 13518603, 13519619, 13519620, 13519648, 13527252, 13527260, 13527261, 13527297, 13527298, 13527827, 13529492, 13529493, 13533809, 13533813, 13533814, 13533817, 13533821. If the BCM is not one of these, the TSB does not apply.
• 13594646 → 13534188 — Standard part replacement/update.
  Heads up: This BCM is explicitly for vehicles 'Without labeled gen iii r'. It will physically fit but is NOT the correct module for the TSB #23-NA-163 procedure and should not be used if that TSB is the suspected cause.

Model Year Variations Within This Range

• 2020-2025: The 2020 model year refresh introduced significant interior electronic changes, including a new rotary controller for the infotainment system, revised center console design, USB-C ports, and optional NFC one-touch phone pairing. While the BCM fault spans the refresh, these changes affect the physical environment where the center console antenna and BCM are located.