U0140 on 2015-2017 Chevrolet Silverado: Lost Communication With BCM Causes and Fixes

What's Unique About the 2015-2017 Chevrolet SILVERADO

For the 2015-2017 Silverado (K2XX platform), this code is strongly linked to specific known issues documented in GM Technical Service Bulletins (TSBs). TSBs PIT5586B and PIT5405C point directly to poor connections at the Serial Data Gateway Module (SDGM) and a bad ground connection at point G218 as the primary causes for U0140 and other communication failures. This makes a wiring and ground inspection the most critical first step, as a faulty module is far less likely than these known connection problems.

Diagnostic Flowchart

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

Symptoms You May Notice

• Multiple warning lights on the instrument panel, such as 'Service StabiliTrak', 'Service Trailer Brake', or 'Park Assist Disabled'.
• Erratic or non-functional interior and exterior lights; dome lights may flash when shifting to reverse.
• Power windows, door locks, or remote keyless entry not working; door locks may cycle on their own.
• Instrument panel display going blank, gauges behaving erratically, or flickering.
• Radio or infotainment system shutting off or going blank.
• Vehicle may not start (no crank), or may start and then immediately stall.
• Wipers continue to run after the truck is off, then stop in the wrong position.
• Loss of power steering assist, especially at low speeds.

Most Likely Causes

1. Poor Ground Connection at G218 🔴 High Probability As documented in GM TSB PIT5405C, sound-deadening insulation was often trapped under the G218 ground terminal during factory assembly, creating a high-resistance connection over time. This is the most widely reported cause by owners and technicians for these specific symptoms.
   How to confirm: Locate ground G218 behind the driver's side kick panel, near the A-pillar. It is a stud with a 10mm nut. Disconnect the battery, remove the ground nut, and visually inspect for trapped black foam insulation or corrosion. A voltage drop test on the ground circuit will show high resistance. Wiggling the wires at the ground may cause symptoms to appear or disappear.
   Typical fix: Remove the 10mm ground nut and terminal. Cut away any interfering insulation, then use sandpaper or a wire brush to clean the contact point on the chassis and the terminal eyelet to bare metal. Re-secure the ground tightly. 🎬 Watch this walkthrough to find and clean the G218 ground. Some owners add a star washer to improve the connection. Reconnect the battery.
   Est. part cost: $0-$5
2. Poor Connection at Serial Data Gateway Module (SDGM) 🔴 High Probability → Shop Telematics Interface Module TSB #PIT5586B and its successor, 20-NA-212, specifically instruct technicians to check the X1 and X2 connectors at the SDGM for terminal concerns like backed-out or bent pins. This module acts as a network router, and a loose or corroded pin can disrupt communication for many systems.
   How to confirm: Locate the SDGM under the driver's side dash, sometimes requiring removal of a lower dash panel. Disconnect the battery, then unplug the connectors (especially the X2 connector) and inspect for loose, bent, or corroded pins. Check for proper terminal tension.
   Typical fix: Clean any corrosion from the pins and connector housing. Ensure all pins have proper tension and re-seat the connector firmly. Applying a small amount of dielectric grease can help prevent future corrosion. In some cases, a damaged terminal or connector pigtail may need to be replaced.
   Est. part cost: $10-$50
3. Low Battery Voltage or Failing Battery 🟡 Medium Probability → Shop Vehicle Battery Modern trucks are highly sensitive to voltage. A weak or failing battery can cause modules to drop off the communication network, especially during engine cranking. This can sometimes occur after a battery replacement if the new battery isn't fully charged or if the system needs a few drive cycles to reset.
   How to confirm: Test the battery with a multimeter; it should read above 12.4 volts with the engine off. Perform a load test, as a battery with a bad cell can cause intermittent voltage drops that trigger communication codes. Check battery cable connections for tightness and corrosion.
   Typical fix: Recharge or replace the vehicle's battery. Ensure terminals are clean and tight.
   Est. part cost: $150-$350
4. Failed Body Control Module (BCM) ⚪ Low Probability → Shop Body Control Module While possible, internal BCM failure is much less common than the connection and ground issues described above. It is often misdiagnosed when the actual problem is at G218.
   How to confirm: This should only be suspected after all wiring, ground, and power supply tests have been completed and confirmed to be good. A professional scan tool will be unable to communicate with the BCM, showing it as 'offline'.
   Typical fix: Replace the Body Control Module. The new module must be programmed to the vehicle's VIN by a dealer or qualified shop to function correctly.
   Est. part cost: $300-$500

Rare But Worth Checking

• Aftermarket Electronics Interference:
• SDGM Logic Lock:

Diagnosis Steps

1. Check and load test the battery to ensure system voltage is stable and above 12.4V. Check all battery cable connections for tightness and corrosion.
2. Scan all vehicle modules with a professional-grade scan tool. Note all 'U' codes and identify which modules are not communicating.
3. Following TSB #PIT5405C, locate and inspect ground G218. It is behind the driver-side kick panel. Disconnect the battery, remove the 10mm nut, check for trapped insulation, clean the contact surfaces to bare metal, and tighten securely.
4. Following TSB #PIT5586B, locate the Serial Data Gateway Module (SDGM) under the driver's dash. Disconnect the battery and inspect its X1 and X2 connectors for loose, corroded, or damaged pins.
5. Check all fuses related to the BCM and SDGM in the interior and under-hood fuse panels.
🎬 See this guide to locate and check your BCM fuses.
6. Perform a hard reset by disconnecting the negative battery terminal for at least 30 minutes. This can sometimes clear a module logic lock.
7. If all connections and fuses are good, use a multimeter and wiring diagram to verify the BCM has proper power and ground at its main connectors.
8. If the BCM has good power and ground but still won't communicate, the module itself is the likely failure point and requires replacement and programming.

Parts You'll Likely Need

• Body Control Module (OEM #13587700) — This part is only needed if all wiring, ground, and connector issues have been ruled out. It is the central computer for body electronics. Part number 13

Related Codes That Often Appear With This One

• U0073 — This general network communication failure code is often set alongside U0140 when a key module like the BCM or SDGM drops off the network, as noted in TSB #PIT5405C.
• U0100 — Lost Communication with ECM. A network disruption caused by the BCM or SDGM can prevent other modules from hearing the engine computer, triggering this code.
• U0101 — Lost Communication with TCM. The Transmission Control Module also communicates on the same network, and its communication can be disrupted by the same root causes.
• U0155 — Lost Communication with Instrument Panel Cluster. Since the BCM sends data to the cluster, a BCM communication failure will often cause the cluster to log this code.
• U0121 — Lost Communication with ABS Control Module. This is another common code set with U0140, as the StabiliTrak system relies on communication between multiple modules.

Technical Service Bulletins (TSBs) & Recalls

• PIT5586B: Instructs technicians to check the Serial Data Gateway Module X2 connector for terminal concerns when multiple communication DTCs are present.
• PIT5405C: Points to checking the body control module ground at G218 for trapped insulation as a cause for multiple communication DTCs and electrical issues.
• 20-NA-212: A more recent bulletin that supersedes earlier TSBs, addressing both SDGM logic locks (requiring a reprogram) and connector terminal issues as causes for widespread communication loss.

Platform-Specific Known Issues

• TSB #PIT5586B specifically calls out checking the Serial Data Gateway Module (SDGM) X2 connector for terminal issues as a cause for U0140 and many other communication codes.
• TSB #PIT5405C identifies a poor ground at location G218 as a common cause for a wide range of communication DTCs, including U0140, often due to trapped insulation under the ground terminal from the factory.
• Owner Experience: G218 Ground Fix: Numerous owners on forums and in YouTube videos have documented fixing a wide array of electrical problems (stalling, no-start, flickering lights) associated with U0140 by simply cleaning the G218 ground. A YouTube video titled 'G218 Ground Issue Fix (2014 - 2018 Chevy Silverado GMC Sierra)' clearly shows the location and the fix, with many comments confirming its success.

Mechanic-Grade Diagnostic Values

• High-Speed GMLAN Bus Resistance — expected: Approximately 60 Ω (Ohms). Failure: A reading of ~120 Ω indicates an open circuit to one of the two terminating resistors. A reading below 55 Ω or above 65 Ω suggests a wiring issue, short, or faulty module.
• Ground Circuit Voltage Drop — expected: < 0.2 Volts. Failure: A reading higher than 0.2V indicates high resistance in the ground connection, which is a common cause of this code at G218.
• CAN Bus Voltage (Key On, Engine Off) — expected: CAN High (Pin 6) should be ~2.5-3.5V and CAN Low (Pin 14) should be ~1.5-2.5V. Both voltages should mirror each other and add up to approximately 5V.. Failure: A short to ground will pull the voltage low; a short to power will pull it high. A short between the two lines will cause both to read around 2.5V with no signal activity.

Hidden / Shadow Codes Worth Checking

• Uxxxx symXX: GM uses 'symptom bytes' (e.g., 'sym71') to add detail to 'U' codes. For example, U0073 sym71 indicates 'Invalid Serial Data Received,' which points more toward data corruption or noise rather than a complete loss of a module. (see via Requires a dealer-level scan tool like a GM GDS2 or a high-end professional scanner capable of reading enhanced GM data.)

Scan Tool Commands That Help

• GDS2 (GM Dealer Tool): Module Status / Network Topology — This is a primary diagnostic step to get a complete overview of the vehicle's networks. It will show which modules are actively communicating and, more importantly, which ones are offline (e.g., the BCM), confirming the U0140 code's origin.
• GDS2 (GM Dealer Tool): BCM Programming/Setup — This function is required after physically replacing the Body Control Module. The new module must be programmed with the vehicle's VIN and specific configuration for it to function correctly.
• GDS2 (GM Dealer Tool): SDGM Programming/Setup — Required after replacing the Serial Data Gateway Module. Similar to the BCM, the new SDGM must be programmed to the vehicle to restore network communication.

Wiring & Ground Locations

• G218 — Behind the driver's side kick panel, near the A-pillar and interior fuse block.. This is the primary ground for the Body Control Module. Factory-installed sound deadening material often gets trapped under the terminal, leading to high resistance and causing the BCM to lose communication. This is the most common fix for U0140 on this platform.
• High-Speed CAN Terminating Resistor (Rear) — On K2XX platform SUVs (Tahoe/Suburban), it's located above the spare tire, taped to the harness near the chassis control module. The location is similar for Silverado pickups.. The CAN bus requires two 120-ohm resistors for proper communication. One is in the ECM, and the other is at the end of the line in the rear. A break in the wiring to this resistor or a failure of the resistor itself will cause the total bus resistance to read 120 ohms instead of 60, leading to network instability.
• Engine Wiring Harness Chafe Points — On the driver's side of the engine bay, the main harness can rub against the sharp edge of the ECM/TCM bracket, the upper control arm, and the shock tower bolt.. While not a direct BCM connection, this harness contains critical power, ground, and data wires for multiple modules. A short circuit in this harness due to chafing can disrupt the entire GMLAN network, causing widespread communication codes, including U0140.
• BCM Connectors (X1-X7) — On the Body Control Module itself, located under the driver's side of the dashboard.. These are the direct connection points to the BCM. Testing for power, ground, and network signals at these connector pins (using a pinout diagram) is the definitive way to determine if the fault is in the vehicle's wiring or internal to the BCM.

Real Owner Repair Stories

• YouTube user comment on video about G218 ground fix (2014-2018 Chevrolet Silverado) — Flickering dash lights, truck suddenly shutting down at low speed, radio shutting down, 'Service Stabilitrak' message.
  ❌ Tried (didn't work) Hours of online research, initial confusion about the cause.
  ✅ What actually fixed it Following a video guide to access the G218 ground behind the driver's kick panel, cleaning the contact surfaces, and re-securing the ground nut. The user reported the fix took 30 minutes and completely solved the truck's issues.
• YouTube user comment on electrical issue video (2014-2018 GM Truck) — Flickering dash lights, truck shutting down, transmission slipping, voltage reading under 14V, radio/nav system shutting down.
  ❌ Tried (didn't work) Assuming it was a major component failure.
  ✅ What actually fixed it The issue was a bad ground connection on the passenger side of the engine block. The user states that over time, rust and dirt caused a poor connection. Removing the bolt, cleaning the contact surfaces and the terminal, and re-installing it fixed all the electrical problems.
• Reddit user r/Silverado (2016 Chevrolet Silverado) — 'Service Stabilitrak' message flashing on the dash intermittently.
  ❌ Tried (didn't work) Driving the truck, as the issue would come and go.
  ✅ What actually fixed it The user identified the problem as the G218 ground after seeing other replies. The confirmed fix was cleaning the poor ground connection located under the dash beside the driver's side audio speaker.

Model Year Variations Within This Range

• 2016-2017: The 2016 model year received a significant mid-cycle refresh, including a new front fascia, different head/tail lights, and an updated MyLink infotainment system with Apple CarPlay/Android Auto. While the G218 ground issue persists, these electrical changes introduce new variables. A GM recall (#15808) was issued for the 2016 model's radio software, which could cause intermittent audio warning failures.