U0140 on 2015-2021 Chevrolet Silverado 1500: BCM Communication Loss Causes & Fixes

What's Unique About the 2015-2021 Chevrolet SILVERADO 1500

For this generation of Silverado, the U0140 code is frequently linked to specific, documented issues. On earlier models in this range (2014-2018, K2XX platform), a poor ground connection for the BCM at location G218 is a known problem explicitly cited by GM in Technical Service Bulletin #PIT5405B. [TSB #PIT5405B] This ground is located behind the driver's side kick panel/A-pillar trim, and sound-deadening material often gets trapped under the connection from the factory, causing a poor contact. On newer models (2019-2021, T1XX platform), the more complex Serial Data Gateway Module (SDGM) can experience 'logic lock' or software issues, also leading to a U0140 code, as noted in TSB #PIT5586G. [TSB #PIT5586G] These platform-specific faults mean diagnosis should start with grounds and gateway module status before suspecting a failed BCM.

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 Silverado generations: the K2XX (2014-2018) and the T1XX (2019-2021). While the code's meaning is the same, a bad BCM ground at G218 is a well-documented issue on the K2XX platform per TSB #PIT5405B. Issues with the Serial Data Gateway Module (SDGM) experiencing 'logic lock' are noted across the range but are particularly relevant to the more advanced T1XX trucks, with GM releasing software updates to address it. [TSB #PIT5586G, 22]

Symptoms You May Notice

• Multiple warning messages on the driver information center (DIC), such as 'Service Stabilitrak' or 'Park Assist Disabled'.
• Radio, climate control (HVAC), and DIC displays going blank or flickering. [TSB #PIT5405B]
• Malfunctioning or inoperative power windows, door locks, and interior lights.
• Erratic or non-working headlights, taillights, or turn signals; lights may flicker when using brakes or turn signals.
• Wipers operating incorrectly or not at all.
• Check Engine Light (MIL) is on.
• Vehicle may not start or may stall, sometimes accompanied by the steering wheel locking up due to loss of electric power steering assist.

Most Likely Causes

1. Poor Body Control Module (BCM) Ground at G218 🔴 High Probability → Shop Body Control Module GM issued TSB #PIT5405B specifically instructing technicians to check ground G218 when multiple communication codes, including U0140, are present. [TSB #PIT5405B] This is a very common factory flaw where sound insulation gets pinched under the ground nut, causing a poor connection.
   How to confirm: Locate ground G218. It is behind the driver's side A-pillar trim, near the emergency brake pedal and under-dash speaker. Visually inspect if the black ground wire's ring terminal is making clean contact with the chassis stud or if foam insulation is trapped underneath. The nut may also be loose.
   Typical fix: Disconnect the negative battery terminal. Remove the driver's side A-pillar and kick panel trim. Locate the 10mm nut for ground G218. Remove the nut and wire terminal. Cut or pull back the foam insulation material away from the stud. Use a wire brush or sandpaper to clean the terminal and the chassis contact surface to bare metal. Re-secure the wire terminal and nut tightly, ensuring a metal-to-metal connection.
   Est. part cost: $0-$10
2. Serial Data Gateway Module (SDGM) Logic Lock or Failure 🟡 Medium Probability → Shop Telematics Interface Module TSB #PIT5586G and its revisions point to a 'logic lock' of the SDGM as a cause for U0140 and a host of other communication codes. [TSB #PIT5586G] This module acts as a network router, and if its microcontroller freezes, communication between networks is lost. This is more common on 2017-2021 models.
   How to confirm: This requires a high-end scan tool to see that multiple modules are offline. A temporary fix that points to logic lock is to perform a hard reset. TSBs suggest pulling the SDGM fuse for one minute. If communication returns, a logic lock was the likely issue.
   Typical fix: A dealership may first attempt to reprogram the SDGM with updated software, as GM has released patches to fix the logic lock anomaly. If reprogramming fails, or if inspection reveals bent/corroded pins on the SDGM connectors (X1, X2), the module will need to be replaced and programmed.
   Est. part cost: $150-$350
3. Damaged Wiring or Corroded Connectors 🟡 Medium Probability Wiring harnesses, especially in areas like the driver's side door sill, A-pillars, or near the firewall, can chafe or corrode over time, causing intermittent shorts or opens in the CAN bus wiring. TSB #PIT4730B notes that even a brief short can take the BCM offline for an entire ignition cycle.
   How to confirm: Visually inspect the wiring harness leading to the BCM (under the driver's dash) and SDGM (often near the BCM) for any signs of chafing, pinching, or corrosion. Unplug the BCM and SDGM connectors and check for corrosion, moisture, or bent pins. Advanced diagnosis involves using a multimeter to check for continuity and resistance on the CAN bus wires (should be ~60 ohms between Pin 6 and Pin 14 at the OBD-II port with the battery disconnected).
   Typical fix: Repair the damaged section of wire with a solder joint and heat shrink. Clean corroded connectors with electrical contact cleaner. If a connector or terminal is severely damaged, it may need to be replaced.
   Est. part cost: $5-$50
4. Failed Body Control Module (BCM) ⚪ Low Probability → Shop Body Control Module While less common than wiring or ground issues, the BCM can fail internally. This was reported by an owner of a 2021 model. [ODI #11623058] Water intrusion from a clogged HVAC drain or a bad windshield seal can also damage the module. It is often misdiagnosed when the G218 ground is the real problem.
   How to confirm: This is typically a process of elimination. If power, ground (G218), and the communication network wiring to the BCM all test good, the module itself is the likely culprit. A scan tool will show the BCM as 'offline' and will be unable to communicate with it.
   Typical fix: Replace the Body Control Module. The new BCM must be programmed by a dealer or a qualified shop with access to GM's Techline Connect software to match the vehicle's VIN and options.
   Est. part cost: $250-$500

Rare But Worth Checking

• Low Battery Voltage or Charging System Fault: → Shop Vehicle Battery A weak or failing battery or alternator can cause system voltage to drop below the threshold required by modules, causing them to shut down and drop off the network intermittently. A U0140 code appearing right after a battery change is a known occurrence and may clear after several drive cycles. Always test the battery and charging system first.
• Blown Fuse: The BCM has multiple power inputs, each protected by a fuse. A single blown fuse can cause a partial or total loss of function and communication. Check all fuses labeled BCM, BODY, or ELEC in the interior (driver and passenger side) and under-hood fuse boxes.
🎬 See this video to quickly locate your BCM fuses.

Diagnosis Steps

1. Check Battery and Charging System: Ensure battery voltage is above 12.4V with the engine off and between 13.7V and 14.7V with the engine running. Low voltage can cause random communication faults.
2. Scan for All Codes: Use a professional scan tool to read codes from ALL modules, not just the engine computer. Note which modules are setting the U0140 code and which, if any, are not communicating at all.
3. Inspect BCM Ground (G218): This is the most critical step for K2XX (2015-2018) models. Locate ground G218 behind the driver's side kick panel. Disconnect the battery, then remove the ground nut. Clean any trapped insulation, sand the contact points to bare metal, and re-secure it tightly.
4. Check for SDGM Logic Lock: For 2017+ models, attempt a hard reset by pulling the SDGM fuse (check owner's manual for location, e.g., F26DL in the underhood fuse box) for 60 seconds, then reinstall. If symptoms disappear temporarily, the SDGM needs a software update or replacement.
5. Inspect Fuses: Check all fuses related to the BCM and SDGM in the interior and under-hood fuse panels.
6. Inspect BCM and SDGM Connectors: Disconnect the electrical connectors and inspect for any signs of corrosion, moisture, or bent/damaged pins.
7. Test CAN Bus Network: If you have an advanced multimeter, disconnect the battery and measure the resistance between Pin 6 (CAN High) and Pin 14 (CAN Low) at the OBD-II port. A healthy network should read approximately 60 ohms.
8. Isolate the Fault: If the above steps do not resolve the issue, the problem likely lies with a failed BCM, a wiring short, or a failed SDGM, which typically requires professional diagnosis.

Parts You'll Likely Need

• Body Control Module (BCM) — The BCM itself can fail, causing the U0140 code. This is the correct part to replace if all power, ground, and network tests are good. A 2021 Silverado owner reported a malfunctioning BCM was the cause. [ODI #11623058]
  Trusted brands: ACDelco (OEM), Dorman
  OEM price range: $300-$500
  Aftermarket price range: $200-$400
• Serial Data Gateway Module (SDGM) — A 'logic lock' or internal failure of the SDGM can cause this code, as noted in TSB #PIT5586G. It is a likely cause if multiple modules on different networks are offline.
  Trusted brands: ACDelco (OEM)
  OEM price range: $150-$350
  Aftermarket price range: $100-$250

Related Codes That Often Appear With This One

• U0073 — Control Module Communication Bus 'A' Off. This is a general network failure code that is often set alongside U0140 when a major module like the BCM goes offline. It is listed in TSBs #PIT5677E, #PIT5713A, #PIT5586G, and #PIT5405B.
• U0100 — Lost Communication with ECM/PCM. If the BCM or SDGM fails, it can prevent other modules from talking to the engine computer. It is listed in TSBs #PIT5677E, #PIT5713A, #PIT5586G, and #PIT5405B.
• U0101 — Lost Communication with TCM. Similar to U0100, the transmission module may lose communication if the BCM or SDGM fails. It is listed in TSBs #PIT5677E, #PIT5713A, #PIT5586G, and #PIT5405B.
• U0155 — Lost Communication With Instrument Panel Cluster (IPC) Control Module. This often appears when the SDGM or BCM fails, as the IPC relies on them for data. It is listed in TSB #PIT5586G.

Technical Service Bulletins (TSBs) & Recalls

• PIT5405B: Mentions checking the BCM ground for multiple DTCs including U0140.
• PIT5586G: Points to a logic lock of the Serial Data Gateway Module as a potential cause.
• PIT5713A: Lists U0140 as part of a combination of DTCs that can appear with multiple IPC warnings.
• PIT5677E: Includes U0140 in a long list of electrical system DTCs.

Platform-Specific Known Issues

• TSB #PIT5405B: Specifically calls out checking the BCM ground on 2015 models when U0140 and other communication codes are present along with blank screens.
• TSB #PIT5586G: Mentions that a 'logic lock' of the Serial Data Gateway Module can cause a host of communication DTCs, including U0140.
• TSB #PIT5713A & #PIT5677E: Both list U0140 as one of many potential codes that can set during widespread electrical or network communication faults.

Mechanic-Grade Diagnostic Values

• CAN Bus Network Resistance — expected: ~60 Ohms. Failure: A reading of ~120 Ohms indicates an open in the bus or a missing terminating resistor. A reading significantly less than 60 Ohms suggests a short between the CAN wires.
• BCM Power Supply Voltage — expected: 12.2V - 12.8V. Failure: Voltage below this range with the ignition on indicates a power supply issue to the module.
• BCM Ground Resistance — expected: < 0.1 Ohms. Failure: Higher resistance indicates a poor ground connection, a primary cause of this code.
• CAN Bus Voltage (Live) — expected: CAN High (CAN+) should be 2.5V-3.5V; CAN Low (CAN-) should be 1.5V-2.5V.. Failure: Voltages that are stuck, flat, or do not mirror each other indicate a network problem like a short to power/ground or a faulty module.

Hidden / Shadow Codes Worth Checking

• U0140 sym00 or U0073 sym71: GM uses 'symptom bytes' (the 'sym' number) to provide extra detail about a communication fault. For example, sym71 on U0073 indicates 'Invalid Serial Data Received'. These codes help a technician understand if the fault is a complete loss of communication or corrupted data. (see via These are typically only visible on a dealer-level scan tool like GDS2 or a high-end professional scanner that can read enhanced GM data.)

Scan Tool Commands That Help

• GDS2 / Techline Connect: Module Reprogramming (SDGM or BCM) — Used to apply software updates that fix known 'logic lock' bugs in the SDGM, as recommended by multiple TSBs. Also used to program a new BCM or SDGM after replacement.
• GDS2 / Techline Connect: Set SDM Primary Key in BCM — This is a mandatory security procedure after replacing and programming a new BCM. It syncs the BCM with the airbag system (SDM - Sensing and Diagnostic Module) and other security components. Failure to do this can leave an airbag light on.

Wiring & Ground Locations

• G218 — Behind the driver's side A-pillar trim, near the emergency brake pedal and under-dash speaker.. This is the primary ground point for the Body Control Module. A poor connection here due to trapped insulation or a loose nut is the single most common cause of U0140 on 2015-2018 models, as documented in TSB #PIT5405B.
• Serial Data Gateway Module (SDGM) — Under the driver's side dash, often requiring removal of a felt footwell cover and a plastic heating vent to access.. This module is the central router for network traffic on T1XX (2019+) trucks. It is prone to 'logic lock' and is the focus of several TSBs related to communication loss codes.
• SDGM Connectors X1 / X2 — These are the main connectors on the Serial Data Gateway Module.. TSBs instruct technicians to inspect these specific connectors for bent, loose, or corroded terminals if a software reprogram does not fix communication issues.
• BCM Fuses (2017-2019) — Driver's side dash fuse box: Fuses 6, 7, 17. Passenger side dash fuse box: Fuses 7, 8, 45, 46.. The BCM is powered by multiple fuses. A failure of any one of them can cause partial or complete loss of function and communication. These specific fuse numbers apply to the mid-generation refresh models.

Real Owner Repair Stories

• Reddit user on r/Silverado (2019 Chevrolet Silverado) — After replacing the battery, the cooling fan continued to run after engine shutoff. A scan at AutoZone revealed code U0140.
  ❌ Tried (didn't work) Disconnecting the battery for 5 hours to try and clear the code.
  ✅ What actually fixed it The consensus from other owners was that U0140 is often set as a history code during a battery change due to the power interruption. The recommendation was to drive the truck for a few days, allowing it to complete several drive cycles, which would cause the history code to clear on its own without any mechanical repair needed.

"I Checked Everything" — The Actual Cause

• A technician may encounter a vehicle where the BCM is completely unresponsive to the scan tool, leading to the assumption that the BCM has failed. However, GM TSB #PIT4730B describes a scenario where an intermittent short on the High Speed GM-LAN circuits (e.g., wires rubbing together over a bump) can cause the BCM to go 'offline' for the entire duration of that ignition cycle. The BCM will not communicate again until the ignition is turned off and the module fully powers down (which can take up to 20 minutes). In this case, the actual root cause is not a failed BCM, but an intermittent wiring short that is no longer present when the vehicle is being tested in the shop. The correct diagnosis is to hunt for the intermittent short rather than replacing the BCM.

Model Year Variations Within This Range

• 2015-2018 (K2XX Platform): The most prevalent cause is a poor ground at G218. Diagnostics should start here almost every time. The network architecture is less complex, with the BCM having more direct control and no separate, primary SDGM.
• 2019-2021 (T1XX Platform): The introduction of the Serial Data Gateway Module (SDGM) as a central network router makes it a common point of failure. 'Logic lock' requiring a fuse pull or a software update via reprogramming is a frequent cause of U0140 on these trucks. Fuse locations and numbers for the BCM also differ from the earlier generation.