U0100 on 2022 GMC Sierra 1500: Lost Communication with ECM Causes and Fixes

What's Unique About the 2022-2022 Gmc SIERRA 1500

For the 2022 GMC Sierra, this code is specifically addressed by a manufacturer's technical service bulletin (TSB #PIT6198) that points technicians toward a diagnostic tip for a "no start" or "check engine light at startup" condition. The bulletin advises testing the accessory wake-up circuit to the ECM for power, suggesting that power delivery issues, rather than a failed ECM, are a primary concern on this specific model year. This platform also relies heavily on a Serial Data Gateway Module (SDGM) to route communications, which has been the subject of several GM service bulletins for both software and hardware issues. TSBs like #PIT5586G and #20-NA-212 describe conditions where the SDGM can experience a "logic lock," retaining power but ceasing all communication 🎬 Watch: Troubleshooting a GMC truck with no communication, or suffer from poor pin connections at its X1 and X2 connectors. Critically, the 2022 model year was a split-year; the 'Refresh' models with the new interior use GM's Vehicle Intelligence Platform (VIP) architecture, which has a different network topology and diagnostic approach than the 'Limited' (pre-refresh) models.

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 (SES/MIL) is on
• Vehicle will not start or has a no-crank condition
• Engine stalls while driving
• Instrument panel gauges sweep or go blank
• Multiple warning messages displayed on the driver information center, such as "Service Safety Restraints System" or "Service Park Assist"
• Reduced engine power ('limp mode')
• Transmission may not shift correctly
• Inoperative A/C controls
• Radio display is blank

Most Likely Causes

1. Wiring or Connector Issue at the ECM 🔴 High Probability GM TSB #PIT6198 specifically directs technicians to check the accessory wake-up circuit to the ECM for power on 2022 models with a U0100 code at startup. This indicates a known potential weakness in this specific circuit or its connections, making it a primary diagnostic starting point.
   How to confirm: Following the TSB, use a multimeter to test the accessory wake-up circuit at the ECM connector for proper voltage during startup. Visually inspect the ECM connectors for corrosion, pushed-out pins, or damage.
   Typical fix: Repairing the specific wire or connector pin. This may involve soldering a new section of wire or replacing the connector pigtail.
   Est. part cost: $10-$50
2. Serial Data Gateway Module (SDGM) Fault 🔴 High Probability → Shop Telematics Interface Module The SDGM acts as the central router for network traffic. GM has issued multiple TSBs (#PIT5586G, #20-NA-212) for SDGM software glitches that can cause it to 'logic lock'—where it powers on but stops communicating—leading to widespread codes like U0100. Physical connector issues at the SDGM are also cited.
   How to confirm: This requires a dealer-level scan tool (GDS2) to check for communication with the SDGM itself. If many modules are offline, the SDGM is a prime suspect. A temporary fix can sometimes be achieved by pulling the SDGM fuse to reset it.
   Typical fix: Reprogramming the SDGM with updated software is the first step for a logic lock issue. If reprogramming fails or terminals are damaged, the module must be replaced and programmed.
   Est. part cost: $75-$150
3. Low Battery Voltage or Poor Battery Connections 🟡 Medium Probability → Shop Vehicle Battery Modern trucks have a high electrical demand. A weak battery or corroded terminals can cause voltage drops during startup that are significant enough to make control modules drop off the communication network.
   How to confirm: Test the battery with a digital multimeter or a load tester. A healthy battery should show at least 12.6 volts with the engine off. Check that the charging system is putting out 13.7-14.7 volts with the engine running. Inspect battery terminals and main power/ground cables for corrosion or looseness.
   Typical fix: Clean the battery terminals and cable ends thoroughly. If the battery fails a load test, it must be replaced. Ensure all connections are secure.
   Est. part cost: $200-$400
4. Poor Ground Connections 🟡 Medium Probability GM has issued engineering inquiries (e.g., #PIE0548) to investigate loose grounds at locations like G110 and G114 on this truck platform. A loose or corroded main engine, body, or ECM ground can prevent modules from communicating properly, causing a cascade of 'U' codes.
   How to confirm: Visually inspect and physically check the main ground straps from the battery to the chassis, the engine block to the chassis, and any smaller ground wires connected to the ECM and BCM. Perform a voltage drop test on the ground circuits.
   Typical fix: Remove the ground connection, clean the contact surfaces of the terminal and the chassis/engine block down to bare metal, and securely retighten. Applying dielectric grease can help prevent future corrosion.
   Est. part cost: $0-$10

Rare But Worth Checking

• Faulty Engine Control Module (ECM): → Shop Engine Control Module (ECM) While this is what the code directly points to, the ECM itself is rarely the true cause. It should only be suspected after all power, ground, and network wiring have been thoroughly tested and confirmed to be good. An owner complaint for a similar 🎬 Watch: Diagnosing a U0100 code and bad ECM on a 5.3L model year did list an ECM fault as a cause.
• CAN Bus Wiring Short/Open: A physical break or a short-to-ground/power in the CAN bus wiring harness itself can take down the network. This can be caused by chafing, rodent damage, or previous improper repairs. Diagnosis involves using a multimeter to check for 60 ohms of resistance across the bus and an oscilloscope to check the signal.
• Aftermarket Device Interference: Poorly installed aftermarket electronics like remote starters, alarms, or even plug-in OBD-II insurance/fleet trackers can interfere with the CAN bus network, causing communication codes. A simple first step is to disconnect any such devices to see if the problem resolves.

Diagnosis Steps

1. Check the battery's state of charge and overall health with a load tester. Ensure terminals are clean and tight.
2. Scan all modules for other DTCs using a capable scanner. A long list of 'U' codes points towards a network-wide issue (like the SDGM or a main power/ground fault) rather than a single module failure.
3. Disconnect any aftermarket electronic devices (remote starters, OBD-II dongles, etc.) to rule out interference.
4. Follow the diagnostic tip in TSB #PIT6198: Specifically test the accessory wake-up circuit going to the ECM to ensure it has power, especially during startup.
5. Inspect the ECM connectors for any signs of water intrusion, corrosion, or damaged/backed-out pins.
6. Inspect the main power and ground connections to the ECM, BCM, and the main chassis/engine grounds (check G110/G114 locations). Perform a voltage drop test on the power and ground circuits.
7. Check the resistance between pins 6 and 14 (CAN High and CAN Low) at the OBD-II port with the battery disconnected. You should see approximately 60 ohms. A reading of 120 ohms indicates an open circuit or a missing terminating resistor, while 0 ohms indicates a short between the two lines.
8. If multiple modules are not communicating, suspect the Serial Data Gateway Module (SDGM). Check for power and ground at the SDGM and verify it is communicating using an advanced scan tool. Inspect its connectors (X1, X2) for backed-out pins.
9. If all wiring, power, grounds, and other modules are confirmed to be good, the ECM itself may be faulty.

Parts You'll Likely Need

• Serial Data Gateway Module (SDGM) (OEM #13534928, 13542838 (Verify with VIN)) — This module is a known failure point that can cause a total network shutdown. TSBs point to software issues requiring reprogramming ('logic lock') or outright failure requiring replacement.
  Trusted brands: ACDelco (GM Genuine)
  OEM price range: $60-$150
  Aftermarket price range: $50-$120
• Engine Control Module (ECM) — This is the part to replace only after all other possibilities (wiring, grounds, SDGM) have been exhausted. It is the most expensive component and one of the least likely to be the root cause despite the code's definition.
  Trusted brands: ACDelco (GM Genuine)
  OEM price range: $400-$800
  Aftermarket price range: $300-$600

Related Codes That Often Appear With This One

• U0140 — Lost Communication with Body Control Module (BCM). This often appears with U0100 because a network-wide failure (like a bad SDGM or power issue) will take multiple critical modules offline simultaneously.
• U0073 — Control Module Communication Bus 'A' Off. This is a general code indicating the entire high-speed CAN bus is down, which is a common root cause for a U0100 code.
• U0101 — Lost Communication with TCM (Transmission Control Module). The TCM and ECM are on the same high-speed network, so a fault that silences the ECM often silences the TCM as well.

Technical Service Bulletins (TSBs) & Recalls

• PIT6198: Diagnostic tip for an SES MIL at startup with DTC U0100, advising to test the accessory wake up circuit to the ECM.
• PIT5586G / 20-NA-212: Describes SDGM 'logic lock' and connector terminal issues causing a host of communication DTCs including U0100.
• PIT5713A: Lists U0100 as one of many potential codes resulting from network issues causing gauges to sweep and multiple warnings.
• PIT5677E: A TSB that includes U0100 in a long list of DTCs related to various electrical issues.
• PIE0548: An engineering inquiry requesting pictures of loose ground connections at G110 and G114 on 2019-2020 models.

Platform-Specific Known Issues

• TSB #PIT6198 specifically notes that for a Service Engine Soon light at startup with DTC U0100, the accessory wake-up circuit to the ECM should be tested for power.
• An owner complaint filed with the NHTSA for a similar model year truck documented code U0100 in conjunction with several other communication and circuit codes, pointing to a complex electrical issue.
• Multiple TSBs for similar GM truck platforms (like #PIT5586G) mention that a host of communication codes, including U0100, can be caused by a 'logic lock' of the Serial Data Gateway Module.

Mechanic-Grade Diagnostic Values

• CAN Bus Network Resistance — expected: Approximately 60 Ohms. 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 suggests a short between the CAN High and CAN Low wires.
• Accessory Wake-up Circuit Voltage — expected: Battery Positive Voltage (approx. 12.6V with key on, engine off). Failure: 0V or significantly low voltage indicates a fault in the power supply circuit to the ECM, as highlighted in TSB #PIT6198.
• Ground Circuit Voltage Drop — expected: < 0.2 Volts. Failure: Voltage higher than 0.2V between a ground point (like the ECM case or G110/G114 stud) and the negative battery terminal indicates a poor ground connection.

Hidden / Shadow Codes Worth Checking

• U0100-00: This is the most common format for this code on GM vehicles. The '-00' symptom byte means 'No Additional Symptom Information,' indicating a general loss of communication without pointing to a specific internal module fault. (see via GM GDS2 or an equivalent high-end bidirectional scan tool.)

Scan Tool Commands That Help

• GDS2 (GM Dealer Scanner): Module Status / Vehicle Wide DTC / Module ID — This is the first step to poll all vehicle networks. It generates a list of which modules are and are not communicating. If many modules are offline, it points to a network-wide issue (SDGM, grounds, main power) rather than a single faulty ECM.
• GDS2 / SPS (Service Programming System): Serial Data Gateway Module Programming — Used to correct the 'logic lock' condition as described in TSBs like #20-NA-212 or to program a replacement SDGM. A service update N212353390 also addresses incorrect SDGM programming from prior service visits.

Wiring & Ground Locations

• G110 — On the lower driver's side of the engine block. It serves as a crucial engine and body harness ground.. GM issued Engineering Inquiry #PIE0548 to investigate loose connections at this specific ground, as it can cause a wide range of communication DTCs, including U0100.
• G114 — On the left front frame rail, near the battery area. It is a primary chassis ground for the engine harness.. Also included in Engineering Inquiry #PIE0548, a poor connection here can interrupt power and ground integrity for multiple modules, leading to network faults.
• Serial Data Gateway Module (SDGM) — Typically located under the driver's side of the dashboard, near the steering column or behind the instrument panel.. This is the central communication hub. TSBs point to both software 'logic lock' and poor connections at its X1 and X2 connectors as a primary cause for network-wide communication loss.
• ECM Accessory Wakeup Serial Data Pin — A specific pin on one of the main ECM connectors (e.g., Pin 7 on the X1 connector in some GM applications).. TSB #PIT6198 specifically calls for testing this pin for power at startup. A lack of voltage here will prevent the ECM from 'waking up' and joining the communication network.

Real Owner Repair Stories

• Forum user reports on GM-Trucks.com and SilveradoSierra.com (2021 Silverado 5.3L) — Intermittent no-start, multiple 'U' codes including U0100, instrument cluster dropping out.
  ❌ Tried (didn't work) Replaced battery, Cleaned all visible ground studs, Dealer reprogrammed multiple modules
  ✅ What actually fixed it The negative battery cable was replaced. It had an internal fracture near the terminal that was not visually apparent. A voltage drop test performed on the cable itself (from the battery post to the frame connection) under load revealed the high resistance.
• Reddit user r/gmcsierra (2022 GMC Sierra Refresh) — Truck brought in for a recall on the Serial Data Gateway Module. During the attempted software update, the module failed and would no longer communicate.
  ❌ Tried (didn't work) Attempting to reprogram the original SDGM multiple times.
  ✅ What actually fixed it The dealer had to replace the Serial Data Gateway Module entirely. The original module failed during the flash process, causing a permanent no-communication state.

OEM Part Supersession History

• 13532121, 13526314 → 13534928 — Internal revisions and software compatibility updates for the Serial Data Gateway Module (SDGM).
  Heads up: Using the wrong SDGM part number can lead to a no-start condition or DTC U1977 (ECU Identification Self Learn Not Completed). The correct part must be ordered by VIN and programmed using SPS.

Model Year Variations Within This Range

• 2022: The 2022 model year is a split between the pre-refresh 'Limited' model (T1 platform, Global A architecture) and the 'Refresh' model with the new interior (T1 platform, Vehicle Intelligence Platform/VIP/Global B architecture). These two electrical systems are fundamentally different. The VIP architecture uses more Ethernet, has a more complex SDGM, and different diagnostic procedures. It is critical to identify which version of the 2022 truck is being worked on, as causes and fixes may not be identical.