U0100 on 2015-2017 GMC Yukon XL: Lost Communication With ECM/PCM Explained

What's Unique About the 2015-2017 Gmc YUKON XL

For this specific generation of GMC Yukon XL and its platform mates (Tahoe, Suburban, Escalade, Silverado, Sierra), General Motors has issued Technical Service Bulletins (TSBs) that directly address the U0100 code. These bulletins, primarily PIT5405C, point technicians toward a known manufacturing flaw with the Body Control Module (BCM) ground point, designated G218. This makes the diagnostic process more targeted compared to other vehicles where U0100 might trigger a more generic and lengthy search for wiring issues.

Diagnostic Flowchart

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

Symptoms You May Notice

• Check Engine Light is on
• Vehicle will not start or is hard to start
• Engine stalls intermittently, especially at low speeds or while turning
• Instrument panel (IPC) goes blank or flickers, speedometer drops to zero
• Radio or HVAC displays go blank
• "Service Stabilitrak" message ap 🎬 Watch: Why the Service Stabilitrak warning appears on GM SUVs.pears
• Reduced or loss of power steering assist, steering wheel may jerk or kick
• Erratic idle
• Alarm sounds randomly when locking doors or door locks cycle
• Wipers park in the incorrect location on the windshield

Most Likely Causes

1. Poor Body Control Module (BCM) Ground at G218 🔴 High Probability → Shop Body Control Module As documented in GM TSBs PIT5405C and its successor 18-NA-161, the dash insulator mat can get trapped under the ground eyelet during assembly, preventing a solid connection. Over time, this poor connection can cause a cascade of communication errors, often triggered by high electrical loads like turning the steering wheel at a stop.
   How to confirm: Visually inspect the G218 ground stud, located inside the cab behind the driver's side kick panel, often near the A-pillar and speaker. Check for a loose 10mm nut or for the black foam dash insulation material being pinched between the ground connector and the vehicle body. A voltage drop test from the BCM ground wire to the chassis will show over 100mV if the ground is poor.
   Typical fix: Disconnect the negative battery terminal. Remove the driver's side A-pillar and kick panel trim. Remove the 10mm ground nut, pull the eyelet(s) off the stud, and trim away any interfering insulation material. Clean the contact surfaces of the eyelet and body with a wire brush or sandpaper to ensure bright metal-to-metal contact, then securely retighten the nut. 🎬 Watch: Step-by-step guide to fixing the G218 ground issue.
   Est. part cost: $0-$5
2. Weak or Failing Battery 🟡 Medium Probability → Shop Vehicle Battery Modern vehicles are highly sensitive to voltage. A weak battery can cause voltage drops during high-load events (like turning the steering wheel at a stop), which can interrupt module communication and trigger numerous codes. TSB PIT5405C lists a faulty battery as a potential cause.
   How to confirm: Load test the battery. A simple voltage check is not enough. Most auto parts stores can perform a load test for free. Also, check that battery cable clamps are tight and not able to spin on the posts. 🎬 See how to replace a faulty GM battery ground cable.
   Typical fix: Replace the battery if it fails the load test. Ensure the new battery terminals are clean and tight, with the posts protruding 1-2mm above the clamps per GM specifications.
   Est. part cost: $150-$350
3. Damaged or Corroded Wiring/Connectors ⚪ Low Probability
   How to confirm: Visually inspect the CAN bus wiring harnesses for any signs of chafing, melting, or corrosion, paying close attention to connectors at the ECM, BCM, and the underhood fuse block. A multimeter can be used to check for 60 ohms of resistance across pins 6 and 14 of the OBD-II port (with the battery disconnected) to verify the integrity of the network's terminating resistors.
   Typical fix: Repair the damaged section of wiring or replace the faulty connector.
   Est. part cost: $10-$200
4. Faulty Control Module (ECM, BCM, SDGM) ⚪ Low Probability
   How to confirm: This should only be considered after all other possibilities (grounds, battery, wiring) have been exhaustively ruled out. Diagnosis requires a high-end scan tool to determine which module is not communicating. The Serial Data Gateway Module (SDGM) can also experience 'logic locks' that cause this code.
   Typical fix: Replace the faulty module. This often requires programming by a dealer or qualified shop. For an SDGM logic lock, sometimes disconnecting the battery or pulling the SDGM fuse can serve as a temporary reset.
   Est. part cost: $400-$1200

Rare But Worth Checking

• Faulty Serial Data Gateway Module (SDGM): → Shop Telematics Interface Module While less common than the G218 ground, other TSBs (like PIT5586G and 20-NA-212) mention the SDGM can experience 'logic locks' or have connector issues that cause widespread communication faults, including U0100. The SDGM is located under the driver's side dash near the steering column.
• Aftermarket Electronics: Improperly installed remote starters, alarms, or audio equipment tapped into the vehicle's data lines can interfere with network communication and cause U-codes.
• Poor Engine/Transmission Ground at G110: → Shop Transmission Assembly A YouTube video by a technician identified a loose or corroded G110 ground as the cause for U0100 and U0101 on a 2015 Yukon. This ground is located on the driver's side of the engine, near the front, behind the power steering pump, and serves as a common ground for the ECM and TCM.

Diagnosis Steps

1. Check and charge the battery. Perform a load test to confirm its health. Ensure terminals are clean and tight.
2. Use a quality OBD-II scanner to pull codes from all vehicle modules, not just the engine. A long list of 'U' codes points to a network-wide problem.
3. CRITICAL STEP: Locate the G218 ground stud in the driver's side footwell/kick panel area, near the A-pillar and speaker.
4. Disconnect the negative battery terminal.
5. Remove the trim panels to access G218. Remove the 10mm nut for the ground. Inspect for any trapped black foam dash insulation material between the connector(s) and the body stud.
6. Regardless of appearance, cut away any interfering insulation. Clean the ground eyelet, the stud, and the body surface with a wire brush or sandpaper to ensure a bright metal-to-metal contact.
7. Securely reinstall the ground connector and nut. Reconnect the battery.
8. Clear all DTCs and perform a drive cycle, including turning the steering wheel lock-to-lock at a stop, to see if the codes return. If they do, further network diagnostics on the CAN bus wiring and other modules (like the SDGM) are necessary.

Parts You'll Likely Need

• No parts needed — The most common fix is cleaning the G218 ground point, which only requires labor.
  OEM price range: $0
  Aftermarket price range: $0
• Battery — A weak battery can cause a variety of electrical issues, including communication codes.
  Trusted brands: ACDelco
  OEM price range: $250-$350
  Aftermarket price range: $150-$250
• Engine Control Module (ECM/PCM) (OEM #e.g., 12673195 (Note: Part number is VIN-specific, this is an example only)) — This is a last resort replacement if the module itself has failed internally after all wiring and ground issues have been ruled out.
  Trusted brands: ACDelco
  OEM price range: $800-$1200
  Aftermarket price range: $400-$800
• Serial Data Gateway Module (SDGM) (OEM #e.g., 13534928, 13542838 (Note: Part number is VIN-specific, these are examples only)) — May require replacement if it has an internal fault or is 'logic locked' and cannot be reset or reprogrammed.
  Trusted brands: ACDelco
  OEM price range: $250-$400
  Aftermarket price range: $150-$300

Related Codes That Often Appear With This One

• U0073 — Control Module Communication Bus 'A' Off. This is a general network code often triggered by the same faults causing U0100.
• U0101 — Lost Communication with TCM (Transmission Control Module). The TCM and ECM share power and ground circuits and are on the same data bus.
• U0121 — Lost Communication with ABS Control Module. A network-wide fault will affect multiple critical modules.
• U0140 — Lost Communication with Body Control Module (BCM). This code is a strong indicator that the G218 ground is the root cause, as it is a primary ground for the BCM.
• C0710 — Steering Position Signal. This code is often set alongside the communication codes when power steering assist is lost.

Technical Service Bulletins (TSBs) & Recalls

• PIT5405C: Addresses multiple communication DTCs, including U0100, and points to a poor BCM ground at G218 as a primary cause. Also mentions faulty batteries and shorted starter cables as other possibilities.
• PIT5405A: An earlier version of the same bulletin, also identifying the G218 ground as a likely culprit for U0100 and other codes.
• 18-NA-161: A later bulletin that supersedes PIT5405C, continuing to address the same set of electrical issues and causes.
• PIT5586G / 20-NA-212: These bulletins address issues with the Serial Data Gateway Module (SDGM) that can cause U0100, such as logic lock-ups or poor connector integrity.

Platform-Specific Known Issues

• TSB #PIT5405C and its successor #18-NA-161 specifically identify a poor BCM ground at G218 as a primary cause for U0100 and a host of other communication and electrical issues on this platform. The fix involves trimming away dash insulation that gets trapped under the ground connector.
• Forum users on tahoeyukonforum.com confirm that cleaning the G218 ground often resolves a dashboard that 'blows up with Service this Service that' and loss of power steering.

Mechanic-Grade Diagnostic Values

• High-Speed CAN Bus Resistance — expected: 60 ohms (+/- 5 ohms) when measured between Pin 6 and Pin 14 of the OBD-II port with the battery disconnected.. Failure: A reading of ~120 ohms indicates an open circuit or a problem with one of the two terminating resistors. A reading near 0 ohms indicates a short between the CAN High and CAN Low wires.
• High-Speed CAN Bus Voltage (Key On, Engine Off) — expected: CAN High (Pin 6) should average ~2.6V. CAN Low (Pin 14) should average ~2.3V. Best measured with an oscilloscope.. Failure: Voltages near 0V or 5V, or voltages that do not mirror each other, indicate a short to ground or power.
• Negative Battery Cable Voltage Drop (while cranking) — expected: Less than 200 mV (0.2V).. Failure: A reading greater than 200 mV indicates high resistance in the negative battery cable or its connections to the engine block and body.
• Positive Battery Cable Voltage Drop (while cranking) — expected: Less than 200 mV (0.2V) from battery post to starter; less than 100mV (0.1V) for the short cable to the fuse block.. Failure: Readings above the specified values indicate high resistance in the cable or connections, a common cause of intermittent module resets.
• ECM Ground Circuit Voltage Drop (Key On, Engine Off) — expected: Less than 100 mV (0.1V).. Failure: A reading greater than 0.3V is unacceptable and points to corrosion or a faulty ground connection for the ECM itself.

Hidden / Shadow Codes Worth Checking

• U0100 with 'Rejected by Control Module' message: In some cases, particularly involving the Power Steering Control Module (PSCM), a U0100 code can become 'latched' or unrecoverable after an electrical event like a short circuit or severe voltage drop. When attempting to clear the code with a scan tool, it may return an error message like 'Rejected by Control Module'. (see via This status is typically seen using the dealer-level GDS2 scan tool when attempting to clear DTCs from the PSCM. TSB #20-NA-206 describes this phenomenon.)

Scan Tool Commands That Help

• GDS2 (GM Dealer Tool): Clear All Modules DTCs — After performing a physical repair (like cleaning ground G218), a global clear command is necessary. Some modules, like the PSCM, may require a specific drive cycle or procedure to clear a latched U0100 code.
• GDS2 (GM Dealer Tool): Steering Angle Sensor Learn — A GM Technical Service Bulletin notes that if a U0100 code is latched in the Power Steering Control Module (PSCM) and won't clear, performing the Steering Angle Sensor Learn procedure may be required before the code can be successfully erased.
• GDS2 (GM Dealer Tool): Module Programming/Setup — If the BCM, ECM, or SDGM is replaced, it must be programmed to the vehicle's VIN and specific configuration using this function. Failure to program a new module will result in a no-start condition and communication codes.

Wiring & Ground Locations

• G218 — Inside the cab, behind the driver's side kick panel, near the A-pillar and speaker.. This is the primary ground for the Body Control Module (BCM). As documented in TSB PIT5405C, dash insulation often gets trapped under this ground during assembly, causing high resistance and a cascade of communication codes, including U0100.
• G110 — On the driver's side of the engine block, sometimes described as being on the rear of the cylinder head or near the power steering pump.. This is a critical ground point for the ECM and TCM. A loose or corroded connection here can directly cause U0100 and U0101 (Lost Communication with TCM).
• CAN Bus Splice Packs (e.g., SP205) — Typically located under the driver's side dash, often above the emergency brake pedal area. They are connectors where multiple data lines join together.. These splice packs are central hubs for the data network. A technician can remove the 'comb' that connects all the circuits to isolate and test the signal from each individual module, helping to pinpoint which one might be corrupting the network.
• Frame Grounds (Front) — On the frame itself, located behind both front wheels.. These grounds are in a terrible location where they are constantly exposed to water and road salt, making them highly susceptible to corrosion. Poor frame grounds can cause a host of intermittent electrical issues.

Real Owner Repair Stories

• CarComplaints.com owner report (2015 GMC Yukon) — Engine turns off while driving. All electrical systems go dead. Wiggling the negative battery cable allows the vehicle to restart.
  ❌ Tried (didn't work) Dealer serviced the vehicle multiple times, replacing the battery and the negative battery cable.
  ✅ What actually fixed it The problem was intermittent and related to a poor connection at the battery, even after cable replacement. The act of wiggling the cable temporarily restored the connection, highlighting the sensitivity of the modules to voltage and ground integrity.
• CarComplaints.com owner report (2015 GMC Yukon) — Sudden flashing of multiple service messages: 'trailer brake service', 'park assist service', 'stability track service'. The engine would rev up and down on its own.
  ❌ Tried (didn't work) The GMC dealer replaced the entire underhood fuse box and all fuses.
  ✅ What actually fixed it The report ends after the fuse box replacement, which was the dealer's proposed fix for the widespread electrical communication failure.

"I Checked Everything" — The Actual Cause

• The diagnostic equivalent for communication codes is 'all wiring tests good'. A common scenario for U0100 on this platform is when all power, ground, and CAN bus resistance tests come back clean. In these cases, the root cause is often a software issue within the Serial Data Gateway Module (SDGM) known as a 'logic lock'. The module's hardware is fine, but its microprocessor has frozen, halting network traffic. This condition cannot be found with a multimeter and requires a dealer-level scan tool to diagnose by observing a total lack of communication from the SDGM, followed by attempting a software reflash to resolve it, as noted in TSB #20-NA-212.

Model Year Variations Within This Range

• 2015: The 2015 model year was a split year for transmissions. Early 2015 models came with a 6-speed automatic transmission, while mid-year 2015.5 models introduced the 8-speed automatic. This can affect diagnostics related to the TCM (U0101) which is often seen with U0100.
• 2017+: Starting in 2017, the 'Air Conditioned Seats' were renamed to 'Vented Seats'. While GM claimed it was just a name change, some owners report a design change and less effective cooling performance compared to 2015-2016 models. This is not directly related to U0100 but reflects a known model year change in dash/seat-related components.