U0100 on 2015-2022 Chevrolet Silverado 1500: Causes and Fixes for Lost ECM Communication

What's Unique About the 2015-2022 Chevrolet SILVERADO 1500

On this generation of Silverado, the U0100 code is frequently linked to specific known issues beyond just a bad ECM. GM has issued several Technical Service Bulletins (TSBs) pointing technicians toward problems with the Serial Data Gateway Module (SDGM) experiencing 'logic lock' (TSB #PIT5586G), issues with the accessory wake-up power circuit to the ECM (TSB #PIT6198), and a poor Body Control Module ground at location G218 (TSB #PIT5405B/C). The G218 ground issue, located under the passenger side dash, is a well-documented cause where sound insulation material gets trapped under the ground connection, causing high resistance and a host of communication failures.

Diagnostic Flowchart

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

Generation note: This year range covers two Silverado 1500 generations: the third-gen (K2XX, 2014-2018) and the fourth-gen (T1XX, 2019-2022). The underlying causes like the G218 ground issue (TSB PIT5405C applies up to 2017 models), SDGM logic locks, and general wiring problems are common across both platforms. However, the physical location of components like the SDGM and specific wiring harness routing may differ slightly between the K2XX and T1XX chassis.

Symptoms You May Notice

• Engine will not start or has a long crank before starting.
• Engine stalls intermittently, sometimes when turning or shifting into reverse.
• Check Engine Light is on, but may disappear and reappear.
• No Check Engine Light at all when the key is turned to the 'ON' position (a key indicator of no ECM communication).
• Multiple other warning lights appear on the dashboard (ABS, StabiliTrak, Park Assist Disabled).
• Instrument panel gauges sweep back and forth randomly or go completely blank while driving.
• A/C controls, radio, or HVAC system become inoperative or go blank.
• Reduced engine power or 'limp mode'.
• Transmission shifts hard.

Most Likely Causes

1. Poor Ground Connection at G218 🔴 High Probability TSB #PIT5405B and #PIT5405C specifically identify the BCM ground G218 as a major issue. The dash insulator mat often gets trapped between the ground eyelet and the body stud, creating a poor connection that leads to numerous communication DTCs, including U0100. This is a very common, well-documented failure point for this platform.
   How to confirm: Visually inspect the G218 ground, located behind the passenger side kick panel/lower dash trim. Check if the dash insulation is interfering with the connection. The nut may also be loose or cross-threaded. Perform a voltage drop test on the ground circuit; it should not exceed 200mV while cranking.
   Typical fix: Remove the ground nut and eyelet. Cut or pull back the dash insulator mat so it no longer interferes with the stud. Clean the contact surfaces and securely reinstall the eyelet and nut.
   Est. part cost: $0-$10
2. Wiring Harness or Connector Issues 🔴 High Probability Vibrations and engine torque can cause wires to break inside the crimped terminal, especially at ground lugs on the engine block. TSB #PIT6198 points to the 'accessory wake up circuit to the ECM' as a known vulnerability. TSB #PIT5405C also points to the B+ battery cable shorting on the starter heat shield.
   How to confirm: Perform a thorough visual inspection of harnesses, especially where they pass over the engine and connect to the ECM, BCM, and fuse block. Wiggle the main harness on the driver's side over the valve cover while the engine is running to see if it causes a stall. Test CAN bus resistance (should be ~60 ohms with the battery disconnected).
   Typical fix: Repair the damaged section of the wiring harness or replace the affected connector pigtail. For broken ground wires, install a new ring terminal. Ensure all connections are clean and secure.
   Est. part cost: $20-$150
3. Faulty Serial Data Gateway Module (SDGM) 🟡 Medium Probability TSB #PIT5586G specifically mentions that a 'logic lock' of the SDGM can cause U0100 along with many other communication codes. This module acts as a router for various CAN bus networks, and its failure can bring down communication between the high and low-speed buses.
   How to confirm: This is difficult to confirm without a high-end scan tool. If multiple modules on different networks are all setting 'lost communication' codes, the SDGM is a prime suspect. A technician may attempt a 'battery disconnect reset' or reprogram the module first. If communication cannot be established with the SDGM, it points to a failure.
   Typical fix: The module may need to be reprogrammed by a dealer. If that fails, it must be replaced and then programmed to the vehicle.
   Est. part cost: $150-$400
4. Low Battery Voltage or Bad Main Grounds 🟡 Medium Probability Modern trucks are packed with electronics that are highly sensitive to voltage drops. Besides G218, main battery cable connections and engine/frame grounds can corrode or loosen, creating high resistance that disrupts module communication.
   How to confirm: Test the battery voltage; it should be above 12.4 volts with the engine off. Perform a voltage drop test on the main power and ground cables during engine cranking. Locate, clean, and tighten all major ground points, especially those on the engine block, frame, and firewall.
   Typical fix: Replace a weak battery or clean/repair the ground connections. This is often a low-cost but highly effective fix.
   Est. part cost: $0-$250
5. Failed Engine Control Module (ECM/PCM) ⚪ Low Probability While possible, the ECM is often replaced unnecessarily. It is a robust component, and the issue is more commonly found in the wiring, power supply, or other modules connected to it.
   How to confirm: This is the last step after all other possibilities have been exhaustively ruled out. A key symptom is the complete absence of the check engine light when the key is in the 'ON' position. A technician will verify the ECM has proper power and ground and that the CAN bus wiring to it is intact before condemning the module.
   Typical fix: Replace the ECM and program it to the vehicle's VIN. This must be done by a qualified shop or dealer. A crankshaft position relearn procedure is often required after replacement.
   Est. part cost: $800-$1500

Rare But Worth Checking

• Faulty Terminating Resistor: The CAN bus network has 120-ohm resistors at each end. On these trucks, they are typically integrated into modules like the ECM and SDGM. If one of these modules fails or a wire breaks leading to it, network resistance will be incorrect (reading 120 ohms instead of 60), causing communication to fail. This is a key step in professional network diagnostics.

Diagnosis Steps

1. Check the battery. Ensure it is fully charged (12.4V+), terminals are clean and tight, and the cable clamps are secure on the posts.
2. Scan for all DTCs in all modules. Note all 'U' codes (U0101, U0140, etc.) as they help identify the scope of the network failure.
3. Confirm the symptom: Turn the key to the 'ON' position. If the Check Engine Light does NOT illuminate at all, this strongly suggests the ECM is not powering up or communicating.
4. Inspect and Clean Ground G218. This is a top priority. Remove the passenger side kick panel and lower dash trim. Locate the ground stud, remove the nut, and ensure the dash insulation is not trapped under the connector. Clean and tighten securely.
5. Visually inspect wiring harnesses. Check for chafing, rodent damage, or burns, especially the main harness on the driver's side engine bank and the B+ cable near the starter heat shield.
6. Perform a CAN Bus Resistance Test. With the battery disconnected, measure the resistance between pins 6 (CAN High) and 14 (CAN Low) at the OBD-II port. A healthy network should read approximately 60 ohms. A reading of 120 ohms indicates an open circuit or a faulty terminating module.
7. Check Fuses and Relays. Inspect fuses related to the ECM, BCM, and ignition systems in both the under-hood and interior fuse panels.
8. If all wiring, grounds, and power checks pass, the issue may be a logic-locked SDGM or a faulty ECM, requiring professional diagnosis.

Parts You'll Likely Need

• Engine Control Module (ECM) (OEM #12674052 (Example for 2017 5.3L)) — This is the part that needs to be replaced if it is confirmed to have failed internally, but only after all other causes are ruled out. Requires programming.
  Trusted brands: ACDelco
  OEM price range: $800-$1500
  Aftermarket price range: $500-$1000
• Serial Data Gateway Module (SDGM) (OEM #13599318 (Example for 2017-2019 models)) — A known failure point on these trucks (per TSB #PIT5586G) that can cause a total network shutdown and trigger a U0100 code. Requires programming.
  Trusted brands: ACDelco
  OEM price range: $150-$400
  Aftermarket price range: $100-$250
• Battery — A weak or failing battery can cause low voltage conditions that disrupt module communication, triggering a U0100 code.
  Trusted brands: ACDelco, Duralast, Optima
  OEM price range: $200-$350
  Aftermarket price range: $150-$300
• Ground Eyelet / Wiring Pigtail — Needed if a ground wire is found broken at the terminal end or if a connector is damaged by corrosion or heat.
  Trusted brands: ACDelco, Dorman
  OEM price range: $15-$50
  Aftermarket price range: $10-$30

Related Codes That Often Appear With This One

• U0073 — Control Module Communication Bus 'A' Off. This is a general bus communication failure code that is often logged alongside U0100 when the entire network goes down. (Cited in TSBs #PIT5677E, #PIT5713A, #PIT5586G, #PIT5405B)
• U0101 — Lost Communication with TCM (Transmission Control Module). The TCM and ECM are on the same high-speed CAN bus, so a network failure often causes both codes to appear together. (Cited in TSBs #PIT5677E, #PIT5713A, #PIT5586G)
• U0140 — Lost Communication with BCM (Body Control Module). This indicates a widespread network issue, as the BCM is a central hub for many vehicle functions and is often affected by the G218 ground fault. (Cited in TSBs #PIT5677E, #PIT5713A, #PIT5586G, #PIT5405B)

Technical Service Bulletins (TSBs) & Recalls

• TSB #PIT6198: Diagnostic tip for an SES MIL at startup with DTC U0100. Instructs dealers to test the accessory wake up circuit to the ECM for power.
• TSB #PIT5586G: Addresses multiple communication DTCs, including U0100, caused by a 'logic lock' of the Serial Data Gateway Module (SDGM).
• TSB #PIT5405B/C: A critical TSB for these trucks. Addresses a wide range of electrical issues (stall, no start, blank dash) caused by a poor BCM ground at G218, a shorted starter cable, or loose battery connections. Lists U0100 as a potential code.
• TSB #PIT5713A: Mentions U0100 in a list of codes related to IPC gauges sweeping and multiple warning messages.
• TSB #PIT5677E: Lists U0100 among dozens of other codes that can be set due to various communication issues.

Platform-Specific Known Issues

• G218 Ground Interference: The most notorious issue for this platform. Sound deadening material from the dash gets caught between the BCM ground eyelet (G218) and the chassis stud behind the passenger kick panel. This creates high resistance and causes intermittent loss of communication with multiple modules. The fix is to trim the material away and clean the connection.
• Starter Solenoid B+ Cable Short: TSB PIT5405C also notes that the starter heat shield can become loose or bent, making contact with the main B+ battery cable terminal on the starter solenoid. This can cause a direct short, draining the battery and causing widespread electrical havoc and communication codes.

Mechanic-Grade Diagnostic Values

• CAN Bus Network Resistance — expected: ~60 Ohms. Failure: A reading of ~120 Ohms indicates an open circuit or a failure of one of the two terminating resistors (modules). A reading near 0 Ohms indicates a short between the CAN High and CAN Low wires.
• CAN Bus Voltage (Key On, Engine Off) — expected: CAN High (Pin 6 at DLC): ~2.5-3.5V. CAN Low (Pin 14 at DLC): ~1.5-2.5V.. Failure: Voltages that are stuck high, low, or at 0V indicate a short to power, short to ground, or an open circuit.
• Battery Voltage (Engine Off) — expected: 12.4V to 12.6V. Failure: Voltage below 12.4V indicates a discharged battery that can cause module communication errors. Voltage below 9.6V can cause modules like the BCM to malfunction.
• 5-Volt Reference Circuit — expected: 5.0V at an accessible sensor (e.g., MAP sensor) with key on.. Failure: 0V on the reference wire suggests the ECM is not powering up or has an internal failure.

Scan Tool Commands That Help

• GDS2 (GM Dealer Tool): Accy/RAP Relay ON/OFF Command — To test the BCM's ability to control the Retained Accessory Power relay, which can be related to the 'accessory wake up circuit' issue mentioned in TSB #PIT6198.
• Professional Bidirectional Scanner: Crankshaft Position Variation Learn — This procedure is required after replacing the ECM to calibrate the new module to the engine's crankshaft position sensor, preventing misfire codes and ensuring proper engine operation.
• Professional Bidirectional Scanner: Module Reprogramming/Setup — When replacing the ECM or SDGM, the new module must be programmed with the vehicle's VIN and specific configuration. This is not an optional step.

Wiring & Ground Locations

• G218 — Behind the passenger side kick panel / lower A-pillar trim, attached to a stud on the body.. This is a primary ground for the Body Control Module (BCM). TSB #PIT5405C identifies it as a common failure point where dash insulation gets trapped, causing high resistance and widespread communication codes, including U0100.
• G103 / G104 — Typically located on the engine block or cylinder head, often on the passenger side. G103 is also cited on the cowl above the brake booster.. These are main engine and component grounds. A loose or corroded connection here can interrupt power/ground to the ECM itself or to critical sensors the ECM relies on.
• DLC (OBD-II Port) Pins 6 & 14 — Under the driver's side dashboard.. Pin 6 is CAN High and Pin 14 is CAN Low. These are the direct test points for measuring the health (resistance and voltage) of the high-speed communication bus that the ECM uses.
• Underhood Fuse Block (IPDM) — In the engine bay, typically on the driver's side.. Loose connections or corrosion within the fuse block itself can cause intermittent power loss to the ECM and other modules, leading to communication codes.

Real Owner Repair Stories

• YouTube channel 'Pro Auto Diagnostics & Programming' (2017 Chevrolet Silverado) — Intermittent no-start, gauges dropping out, loss of power steering, multiple communication codes.
  ❌ Tried (didn't work) Initial inspection was inconclusive.
  ✅ What actually fixed it Diagnosis found two issues: 1) A CAN bus resistance of 120 ohms (instead of 60), indicating a missing terminating resistor. 2) Poorly done butt connectors on the Transmission Control Module (TCM) connector from a prior repair were causing an open circuit. The ECM also showed signs of internal resistance failure. The primary fix was to properly repair the TCM connector.
• YouTube channel 'How to diagnose' (Chevrolet/GMC Truck (model year not specified, but K2XX body style)) — No-start, no-crank condition. All dash lights come on but no action when turning key to 'start'.
  ❌ Tried (didn't work) Owner replaced fuel pump, battery, spark plugs, coils, and alternator. Technician checked fuel pressure and main grounds, which were all good.
  ✅ What actually fixed it The final diagnosis was a failed ECM. The key diagnostic indicator was the complete absence of the Check Engine Light when the key was turned to the 'ON' position, confirming the ECM was not communicating at all. Replacing and programming the ECM resolved the issue.
• Chevy HHR Network forum user (GM Vehicle (HHR, but symptoms are analogous)) — Hot-start failure (acted like dead battery), then after jump start, had U0100, hard shifting, and loss of power steering.
  ❌ Tried (didn't work) Pulling a maxi fuse did not clear the code.
  ✅ What actually fixed it Disconnecting the negative battery cable for 20 minutes and reconnecting it. This full reset cleared the U0100 code and all symptoms disappeared, suggesting a module 'logic lock' or temporary glitch rather than a hard part failure.

OEM Part Supersession History

• e.g., 12673195, 12673676 → Varies by year and engine — Software updates and hardware revisions.
  Heads up: A replacement ECM is not plug-and-play. It MUST be programmed with the vehicle's VIN to communicate with other modules like the BCM and TCM. Failure to program will result in a no-start condition and communication codes. A crankshaft position relearn is also typically required.

Model Year Variations Within This Range

• 2015-2018 (K2XX) vs 2019-2022 (T1XX): The vehicle architecture changed from the K2XX to the T1XX platform in 2019. While the principles of CAN bus diagnosis are the same, the physical locations of the Serial Data Gateway Module (SDGM), ECM, and specific ground points (e.g., G103, G104) may vary between generations. Always verify component location with a service manual for the specific model year.