U0422 on 2017-2020 GMC Sierra 1500: Invalid BCM Data Causes and Fixes

What's Unique About the 2017-2020 Gmc SIERRA 1500

The 2017-2020 GMC Sierra spans two generations (K2XX and T1XX) with increasingly complex vehicle networks. A key component in this network is the Serial Data Gateway Module (SDGM), which acts as a router between different data buses. 🎬 See how an SDGM bypass harness is installed in this network. GM has specifically identified the SDGM as a point of failure in technical service bulletins for communication issues, including logic lock-ups and connector problems that can trigger a U0422 code. 🎬 Watch: A quick walkthrough of the U0422 code on Chevy trucks. TSB PIT5586G is a crucial document for 2017 models, explicitly pointing to the SDGM and its connectors as the primary cause for a host of communication DTCs, including U0422.

Diagnostic Flowchart

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

Generation note: This range covers the end of the third generation (K2XX, 2017-2018) and the beginning of the fourth generation (T1XX, 2019-2020). While the electrical architecture differs, the U0422 code is relevant to both, often pointing to issues with central communication modules like the BCM and SDGM. TSB PIT5586G is particularly relevant for 2017 K2XX models. TSB 20-NA-155 addresses software issues on 2020 T1XX models.

Symptoms You May Notice

• Multiple warning messages on the instrument panel (e.g., 'Service Stabilitrak').
• Check Engine Light (MIL) is on.
• Service 4WD message may appear.
• Instrument cluster gauges may drop to zero or behave erratically.
• Interior or exterior lights may flicker, stay dim, or not work at all.
• Power door locks may not respond.
• Power windows may move slowly or erratically.
• Turn signal sounds or other chimes may be absent.
• Radio display may be blank or not shut off when the door is opened.
• Vehicle may not start or may start and then immediately stall.

Most Likely Causes

1. Wiring or Connector Issues at the Serial Data Gateway Module (SDGM) 🔴 High Probability GM TSB #PIT5586G specifically calls out checking the X1 and X2 connectors on the SDGM for bent, backed-out, or loose terminals on 2017 models. This indicates a known weakness and a primary diagnostic step.
   How to confirm: Visually inspect the SDGM connectors for corrosion, moisture, or backed-out/loose terminals. The SDGM is a small box located in the driver's side footwell, above the pedals. A technician can perform a pin-drag test to check for proper terminal tension.
   Typical fix: Repairing the wiring, cleaning the connector terminals, or replacing the connector pigtail if damaged.
   Est. part cost: $10-$50
2. Serial Data Gateway Module (SDGM) Logic Lock or Software Anomaly 🟡 Medium Probability Modern modules can enter a 'logic lock' state. TSB #PIT5586G mentions this possibility, instructing technicians to perform a reset by pulling the SDGM fuse before replacing parts. TSB #20-NA-155 points to software anomalies causing communication DTCs on 2020 models.
   How to confirm: A 'hard reset' by disconnecting the battery or pulling the specific SDGM fuse (F26DL for trucks) for a minute may temporarily resolve the issue. A dealer or qualified shop can check if a software update is available for the SDGM or other related modules.
   Typical fix: Performing a reset by pulling the SDGM fuse. If the issue persists, reprogramming the module with the latest software is the next step. In some cases, the module itself must be replaced.
   Est. part cost: $0-$400
3. Weak or Failing Battery / Poor Connections 🟡 Medium Probability The complex electronics on modern trucks are highly sensitive to voltage. A battery that is failing or has corroded terminals can cause random communication codes as modules fail to initialize correctly.
   How to confirm: Test the battery with a multimeter; it should read above 12.4 volts at rest. Check the battery terminals and main ground connections for tightness and corrosion.
   Typical fix: Clean the battery terminals and cable ends thoroughly. If the battery fails a load test, it must be replaced.
   Est. part cost: $0-$250
4. Faulty Body Control Module (BCM) ⚪ Low Probability While less common than wiring or SDGM issues, the BCM is the module sending the 'invalid data' and can fail internally. This is often a diagnosis of last resort after all other possibilities are exhausted.
   How to confirm: This is typically a process of elimination. If all wiring, connections, and other modules are confirmed to be good, the BCM becomes the primary suspect. A bi-directional scan tool can help test BCM functions.
   Typical fix: Replacement of the Body Control Module, which requires programming to the vehicle's specific VIN and options.
   Est. part cost: $250-$500

Rare But Worth Checking

• Aftermarket Accessories:
• Corrupted Tuning Software Cache:

Diagnosis Steps

1. Check and record all Diagnostic Trouble Codes (DTCs) from all available modules using a professional-grade scan tool.
2. Inspect the battery and charging system. Ensure battery voltage is stable and above 12.4V with the engine off. Clean any corrosion from terminals.
3. Consult GM Technical Service Bulletins. Specifically check for PIT5586G (2017 models) and 20-NA-155 (2020 models) which directly address communication codes.
4. Perform a 'logic lock' reset by pulling the SDGM fuse (F26DL in the engine bay fuse block for trucks) for at least 60 seconds, then reinstall it and re-check for codes.
5. Locate and inspect the Serial Data Gateway Module (SDGM) in the driver's side footwell. Carefully inspect its connectors (X1 and X2, often gray and black) for any signs of damage, corrosion, or loose pins as per TSB PIT5586G.
6. If aftermarket accessories are installed, temporarily disconnect them to see if the issue resolves.
7. If TSB 20-NA-155 applies (2020 models), have a dealer reprogram the Brake System Control Module (BSCM).
8. If no wiring or software issues are found, further diagnostics with a bi-directional scanner are needed to isolate whether the BCM or SDGM has failed internally.

Parts You'll Likely Need

• Serial Data Gateway Module (SDGM) (OEM #84525623 (2019-2020 T1XX), 84448288 (2017-2018 K2XX) - Part numbers can vary, always verify with VIN.) — Identified in TSBs as a common point of failure for communication issues, either through software lock-ups or internal faults.

Related Codes That Often Appear With This One

• U0073 — Control Module Communication Bus 'A' Off. This is a general network code often set alongside more specific codes like U0422 when a major communication disruption occurs.
• U0100 — Lost Communication With ECM/PCM. This indicates the network problem is affecting communication with the engine computer.
• U0140 — Lost Communication With Body Control Module. This is a companion code to U0422, indicating other modules cannot hear from the BCM at all, in addition to receiving invalid data from it.
• P25A2 — Brake System Control Module Requested MIL Illumination. On some 2020 models, a software issue in the Brake System Control Module (BSCM) can cause it to set communication codes like U0422 after shutdown, which then asks the ECM to turn on the Check Engine Light.

Technical Service Bulletins (TSBs) & Recalls

• PIT5586G: Diagnostic Tip - IPC Gauges Inoperative or Fluctuate, No Crank, Start then Stall. Directly addresses U0422 and points to SDGM connector terminals and logic lock.
• 20-NA-155: Service Engine Soon Message at Start Up. Addresses a software anomaly in the Brake System Control Module (BSCM) on 2020 models causing U-codes including U0422. Fix is a software update.
• PIT5713A: Multiple IPC warning messages and MIL displayed. Lists U0422 as one of many potential codes in a general communication failure scenario.
• 16-NA-407: Information on Chassis Control Module (CCM) Receives Invalid Data and Sets DTC U0422. While for other GM vehicles, it explains how high bus traffic on startup can cause a module to temporarily report invalid data, leading to a stored U0422. It advises ignoring the code unless it is active or accompanied by other specific BCM faults.

Platform-Specific Known Issues

• TSB #PIT5586G points to a potential 'logic lock' of the Serial Data Gateway Module or terminal issues in its connectors as a cause for U0422 and other communication codes on 2017 models. The first recommended step is to pull the SDGM fuse to reset it.
• TSB #PIT5713A lists U0422 as one of many possible codes resulting from a general communication failure causing multiple instrument panel warnings on 2020 models.
• TSB #20-NA-155 describes a software anomaly in the Brake System Control Module (BSCM) on 2020 models that can cause it to set U0422 after shutdown, which can be fixed with a software update.

Mechanic-Grade Diagnostic Values

• CAN Bus Resistance at DLC — expected: Approximately 120 Ohms on each bus pair (e.g., pins 6 & 14, 3 & 11).. Failure: A reading of 60 Ohms or an open circuit at the DLC could indicate an issue, though 120 Ohms is normal for these gateway-equipped trucks. This differs from older systems where 60 Ohms is expected.
• CAN Bus Voltage (Key On) — expected: CAN High (CAN_H) wire should toggle between ~2.5V (recessive) and ~3.5V (dominant). CAN Low (CAN_L) should toggle between ~2.5V (recessive) and ~1.5V (dominant).. Failure: A static voltage (e.g., stuck at 2.5V) indicates the bus is idle or a module is not transmitting. Voltages shorted to ground (0V) or power (~5V or 12V) indicate a wiring fault.
• Battery Voltage (At Rest) — expected: Greater than 12.4 Volts.. Failure: Voltage below 12.4V indicates a discharged or failing battery, which is a known cause of random communication codes on modern vehicles.

Hidden / Shadow Codes Worth Checking

• Symptom Bytes: While not a specific code, the GM GDS2 scan tool can read additional 'symptom bytes' associated with a main DTC like U0422. These provide more granular detail about the nature of the fault (e.g., 'signal invalid', 'signal erratic') that is not visible on standard OBD-II readers. (see via Requires a professional scan tool with manufacturer-specific software, such as the GM GDS2.)

Scan Tool Commands That Help

• GM GDS2 (Global Diagnostic System 2): Module Diagnostics > SDGM > Data Display — Use this function to see if the Serial Data Gateway Module is online, processing information, and communicating with other modules, even if it's the source of the invalid data.
• GM GDS2 (Global Diagnostic System 2): Module Diagnostics > Vehicle DTC Information — This is the first step to perform a full network scan. It reveals which modules are reporting codes and, more importantly, which modules are not responding at all, helping to pinpoint the location of a communication breakdown.
• GM SPS (Service Programming System): Gateway Module Replacement/Programming — This function is mandatory after physically replacing the Serial Data Gateway Module. The new module must be programmed with the vehicle's VIN and specific configuration to function correctly on the network.

Wiring & Ground Locations

• G110 / G114 — On 2019-2020 T1XX models, these are key grounds for the body and engine harnesses.. GM issued a specific Engineering Information bulletin (PIE0548) for technicians to document loose connections at these exact ground points, indicating they are a known source of various electrical issues. A poor ground here can cause intermittent communication faults.
• G218 — Located on the driver's side, under the dash, near the A-pillar and often behind the kick panel.. This is a major ground distribution point for many instrument panel and driver-side components. An intermittent connection at G218 can cause a wide range of seemingly unrelated electrical faults and communication codes originating from modules grounded at this point.
• SDGM Connectors (X1/X2) — On the Serial Data Gateway Module, located in the driver's side footwell above the pedals.. TSB PIT5586G explicitly identifies these connectors as a primary failure point due to bent, loose, or backed-out terminals, directly causing communication codes like U0422.
• F26DL (Fuse) — In the underhood fuse block on trucks.. This is the power feed fuse for the Serial Data Gateway Module (SDGM). TSBs instruct technicians to pull this specific fuse for at least 60 seconds to perform a 'logic lock' reset on the module before attempting replacement.

Real Owner Repair Stories

• YouTube channel 'Pine Hollow Auto Diagnostics' (2020 GMC Sierra) — A flood of intermittent warning messages on the dash ('Service Safety Restraint System', 'Service Side Detection', 'Service Park Assist') and numerous U-codes related to the low-speed CAN network.
  ❌ Tried (didn't work) The technician confirmed CAN bus resistance was 120 ohms at the DLC (which is normal for this truck). The CAN signal waveform on an oscilloscope was clearly corrupted when the fault was active.
  ✅ What actually fixed it The diagnostic process involved isolating the faulty network segment. The technician began pulling fuses one-by-one for every module on the low-speed CAN bus (e.g., seat memory module, trailer light module) while watching the live oscilloscope pattern. The goal was to see the corrupted signal return to a clean square wave the moment the problematic module was powered down. This methodical isolation is the professional approach when a network-wide fault occurs.
• YouTube video regarding HP Tuners (General GM vehicle, applicable to tuned Sierras) — U0422 code appeared immediately after flashing a new engine tune to the vehicle.
  ❌ Tried (didn't work) Diagnosing the vehicle's hardware (wiring, modules) would show no faults, as the problem is not with the truck itself.
  ✅ What actually fixed it The problem was a corrupted data cache within the HP Tuners VCM Suite software on the laptop, often caused by connecting to multiple different vehicles. The fix was to 1) Uninstall the VCM Suite from the computer, 2) Manually navigate to the 'My Documents' folder and delete the 'HP Tuners' folder entirely, and 3) Reinstall the software. This clears the corrupted cache, allowing a clean file to be written to the vehicle.

"I Checked Everything" — The Actual Cause

• The network equivalent of a 'smoke test clean' scenario is when all wiring, connectors, and grounds check out perfectly, yet the communication code persists. In one documented case, the root cause was not in the vehicle's hardware at all, but in corrupted data from an external aftermarket tuning tool (HP Tuners). The tool's software cache was corrupted, causing it to write a bad file that triggered the U0422 code. The fix was to completely purge and reinstall the tuning software on the PC.

When the Usual Fixes Don't Work

• While TSBs point to faulty SDGM connectors as a primary cause, simply cleaning visible corrosion on the power pins may not be sufficient. In one documented case, a user replaced the SDGM and cleaned a corroded power pin, but the communication fault persisted. Further diagnosis pointed towards a 'wake up' signal from the BCM not reaching other modules, indicating a more complex network issue than just a single bad connection.

Model Year Variations Within This Range

• 2019-2020 (T1XX Platform): A GM Engineering Information bulletin (PIE0548) was issued specifically for these model years regarding loose ground connections at G110 (Body Harness) and G114 (Engine Harness), indicating a known production issue not highlighted for earlier years.
• 2017-2020 (All): Due to the presence of the Serial Data Gateway Module (SDGM), the expected CAN bus resistance when measured at the Data Link Connector (DLC) is 120 Ohms, not 60 Ohms. Technicians accustomed to older, non-gateway networks may misdiagnose this normal reading as a fault (an open circuit or missing termination resistor).
• 2017-2019 (K2XX Platform) vs 2019-2020 (T1XX Platform): The network architecture changed enough that some aftermarket devices require an 'SDGM bypass harness' for the K2XX trucks, but the same device does not require the harness for the newer T1XX trucks. This points to differences in how the gateway module routes data, particularly for infotainment and diagnostics.