B3925 on 2019-2024 Chevrolet Malibu: No-Start Causes and Fixes

What's Unique About the 2019-2024 Chevrolet MALIBU

The ninth-generation Malibu and its platform mates (Buick Regal, Cadillac XT4, Chevy Equinox) use a GEN3R Body Control Module (BCM) that is highly susceptible to this specific software corruption. GM has issued multiple Technical Service Bulletins (TSBs) because a simple voltage drop can disable the vehicle, leading to a common misdiagnosis of a failed BCM. Unlike many codes that point to a bad part, B3925 on this Malibu almost always points to a software issue that requires a specific reprogramming procedure, not a hardware replacement.

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 ('No Crank, No Start').
• Engine starts briefly and then immediately stalls.
• "No FOB Detected" message on the driver information center.
• Key fobs are inoperative for both locking/unlocking (active functions) and push-to-start (passive functions).
• Security light may be flashing on the instrument cluster.
• Multiple unrelated warning lights may appear on the dash.

Most Likely Causes

1. Body Control Module (BCM) Memory Corruption 🔴 High Probability → Shop Body Control Module The GEN3R BCM used in these vehicles is sensitive to low voltage events, which can corrupt its software configuration data, specifically the 'Environmental Identifier'.
   How to confirm: A professional technician will use a GM GDS2 scan tool. They will look for code B389A and three or more 'Environment ID' DTCs (B3924, B3925, B3926, B3927) stored in the BCM. TSB #23-NA-163 specifically instructs technicians to check for these codes as a group.
   Typical fix: The BCM must be reprogrammed by a dealer or qualified shop following the specific procedure in TSB #23-NA-163. This involves a special 'Special Data Reset A' or 'Special Data Reset B' function, followed by an immobilizer relearn with the existing keys. No new parts are typically required.
   Est. part cost: $0
2. Low Voltage Event (Trigger) 🔴 High Probability This is the trigger for the BCM memory corruption. A weak or failing battery, jump-starting the vehicle, replacing the battery, or even a temporary poor connection can initiate the fault.
   How to confirm: The issue appeared immediately after the battery was replaced, jump-started, went dead, or was disconnected.
   Typical fix: The underlying BCM corruption must be fixed via reprogramming per TSB #23-NA-163. The battery should also be fully charged and tested, and replaced if it is weak, to prevent recurrence.
   Est. part cost: $150-$350 for a new AGM battery if needed.

Rare But Worth Checking

• Failed Body Control Module (BCM): → Shop Body Control Module While the TSBs point to a software issue, it is possible for the BCM hardware itself to fail (e.g., from an internal short or cracked solder joints). This should only be considered after the reprogramming procedure from TSB #23-NA-163 fails to resolve the issue.
• Wiring Harness Issue: A damaged wire or poor connection to the BCM could cause communication errors that mimic this fault. A Reddit user with a 2018 Equinox reported a similar no-start BCM issue was ultimately traced to a shorted wire near the rear differential.

Diagnosis Steps

1. Confirm the primary symptoms: No crank/no start, key fobs are not working.
2. Check and stabilize the battery. Ensure it has a full charge (above 12.6V) and can hold a load. A weak battery can cause reprogramming to fail.
3. Connect a professional scan tool capable of reading GM body codes (like a GM GDS2).
4. Scan the Body Control Module (BCM) for codes. Confirm the presence of B389A along with three or more environmental ID codes (B3924, B3925, B3926, B3927).
5. If these specific codes are present, DO NOT replace any modules or attempt a standard immobilizer relearn first.
6. Provide the technician with TSB #23-NA-163 and request they follow the specified software recovery procedure.
7. The procedure involves using GM's Service Programming System (SPS) to run a special function called 'Programming A Per Bulletin 23-NA-163' or 'Special Data Reset B', followed by an immobilizer relearn with the existing keys.

Parts You'll Likely Need

• Body Control Module (BCM) Reprogramming — This is a software fix, not a hardware part. It is the primary solution outlined by GM in TSB #23-NA-163 to correct the memory corruption that causes code B3925.
  OEM price range: $150-$400 (Labor for diagnosis and programming)
  Aftermarket price range: N/A
• Body Control Module (OEM #13532705) — Only needed in the rare case that the BCM hardware has failed and will not accept the reprogramming procedure. A replacement BCM must be programmed by a professional. Note: Part number 13532705 is listed for other GM vehicles like the Colorado and may not be the exact part for all Malibus; always verify by VIN.
  Trusted brands: ACDelco (GM Genuine)
  OEM price range: $300-$500
  Aftermarket price range: $150-$350 (Remanufactured/Cloned)

Related Codes That Often Appear With This One

• B3924 — Incorrect Environmental Identifier from the Inflatable Restraint Sensing and Diagnostic Module. It is part of the same software corruption event.
• B3926 — Incorrect Environmental Identifier from the Instrument Cluster. It is part of the same software corruption event.
• B3927 — Incorrect Environmental Identifier from the Electronic Brake Control Module. It is part of the same software corruption event.
• P0513 — This code means 'Invalid Immobilizer Key'. It is set because the BCM's memory corruption prevents it from recognizing the programmed key fobs.
• B389A — This code for 'Environment Identification' is a key indicator that multiple modules have lost their configuration, and TSB #23-NA-163 specifically calls for checking for this code as the primary condition.

Technical Service Bulletins (TSBs) & Recalls

• 23-NA-163: The most current bulletin, it provides a specific two-path software repair procedure ('Programming A' or 'Programming B') using the GDS2/SPS to correct the BCM memory corruption causing the no-start condition. It explicitly warns against replacing modules before performing this procedure.
• 21-NA-277: An earlier bulletin, now superseded, that also identified the no-start condition linked to B3925 and other environmental ID codes after a low-voltage event. It required contacting the GM Technical Assistance Center (TAC) for a special VCI number to perform the reset.

Platform-Specific Known Issues

• The GEN3R Body Control Module in these vehicles is highly sensitive to voltage fluctuations, making this a common issue after a battery replacement or jump-start.
• GM has issued multiple TSBs (including #23-NA-163 which supersedes #21-NA-277) specifically to address this software corruption issue, instructing technicians to reprogram the BCM rather than replace it.

Mechanic-Grade Diagnostic Values

• High-Speed GMLAN Bus Voltage (At Rest) — expected: Approximately 2.5V on both GMLAN-High (Pin 6 at DLC) and GMLAN-Low (Pin 14 at DLC) circuits, with a differential voltage near 0V.. Failure: Significant deviation from 2.5V on either line, or a constant non-zero differential voltage, indicates a short to power, ground, or an internal module fault.
• High-Speed GMLAN Bus Voltage (Active Communication) — expected: GMLAN-High toggles to ~3.5V and GMLAN-Low toggles to ~1.5V, creating a ~2.0V differential to represent a logic '0'.. Failure: A flat line or lack of toggling during a command indicates a communication breakdown.
• System Voltage During Programming — expected: Stable voltage above 11.5V, ideally maintained with a dedicated programming power supply.. Failure: Voltage dropping below 11.5V can interrupt and fail the BCM reprogramming procedure.

Hidden / Shadow Codes Worth Checking

• B389A with 3+ Environment ID DTCs: This is the primary diagnostic condition. If B389A is not present despite symptoms, the TSB advises a battery disconnect/reconnect for at least 30 seconds to try and force the code to set. (see via GM GDS2 Scan Tool in the K9 Body Control Module data.)

Scan Tool Commands That Help

• GM GDS2 / SPS: Navigate: GDS2 > Module Diagnostics > [K9] Body Control Module > Identification Information — This is the first step before attempting any programming to verify the BCM is a 'GEN3R' type and that its Base Model Part Number (BMPN) is on the list of eligible modules in TSB #23-NA-163.
• GM GDS2 / SPS: Programming A Per Bulletin 23-NA-163 and 23-NA-165 Only — This is the primary software recovery procedure for a vehicle that has not had a previous failed immobilizer learn attempt.
• GM GDS2 / SPS: Special Data Reset B (or Programming B Per Bulletin 23-NA-163 Only) — This is the secondary recovery procedure to be used ONLY if a standard immobilizer learn was already attempted and failed to fix the issue.
• GM GDS2 / SPS: Body Control Module IMMO Learn with Existing Transponder or Remote Key — This immobilizer relearn must be performed immediately after running 'Programming A'.

Wiring & Ground Locations

• K9 Body Control Module (BCM) — Located behind the kick panel in the front passenger footwell.. This is the module that requires reprogramming and is the central hub for the fault. Physical access is needed for replacement, and checking its connectors for security and corrosion is a basic diagnostic step.
• BCM Fuses (Interior) — In the instrument panel fuse block, located on the driver's side of the dash. Check fuses F20, F21, and F41.. A blown fuse can cause a loss of power to the BCM, leading to a no-communication state that could be misdiagnosed as a failed module.
• BCM Fuse (Underhood) — In the underhood fuse block, located on the passenger side of the engine bay. Check fuse F35 (a double fuse).. This is another critical power source for the BCM. Loss of this fuse could cause a no-power or intermittent power condition.
• G103 (Ground) — Likely located at the left rear of the engine compartment on the cowl, above the brake booster.. Service information for similar GM platforms indicates G103 is a primary ground for the BCM, Instrument Panel Cluster (IPC), and Data Link Connector (DLC). A loose or corroded G103 can cause widespread communication and module power issues, mimicking a failed BCM.

OEM Part Supersession History

• Multiple (See List) → N/A — TSB #23-NA-163 applies to a specific list of GEN3R BCM Base Model Part Numbers (BMPNs). It is critical to verify the vehicle's BCM part number is on this list before proceeding. The part number 13532705 is NOT on this list.
  Heads up: Eligible BMPNs from TSB #23-NA-163 include: 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 on this list, the TSB does not apply.

Model Year Variations Within This Range

• 2019-2024: The diagnosis is not strictly based on model year but on the hardware installed. The fix outlined in TSB #23-NA-163 ONLY applies to vehicles equipped with a GEN3R Body Control Module. A technician must verify this using the GDS2 scan tool before proceeding, as other BCM types may be present even within the same model year.