U0155 on 2017-2020 Chevrolet Silverado 1500: Instrument Cluster Communication Loss Causes and Fixes

What's Unique About the 2017-2020 Chevrolet SILVERADO 1500

On the 2017-2020 Silverado, which spans the K2XX and T1XX generations, this code is frequently linked to issues beyond a simple failed cluster. Manufacturer bulletins point to software glitches ('logic lock') in the Serial Data Gateway Module (SDGM) or poor terminal tension in its connectors as the primary culprits. The SDGM acts as a central router for network data, and its location high in the driver's footwell makes it susceptible to connection issues. This means a seemingly unrelated part can be the source of the communication loss with the instrument panel, making diagnosis more complex than on older, simpler vehicles.

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 the end of the 3rd generation (K2XX; 2017-2018, plus 2019 LD) and the beginning of the 4th generation (T1XX; 2019-2020). While the code's meaning is the same, TSBs indicate different specific causes. TSB #PIT5586G, which points to the SDGM logic lock and connector issues, applies to the K2XX platform. TSB #20NA021 applies to the 2020 T1XX platform, pointing to a specific issue with the steering column lock module.

Symptoms You May Notice

• Instrument cluster is completely blank or dead.
• Gauges (speedometer, tachometer, fuel) stop working, freeze, or fluctuate erratically.
• All warning lights turn on, or none of them work.
• Radio display may go blank or fail to turn off when the door is opened.
• No audible chime for turn signals, although exterior lights still function.
• Intermittent "Service Steering Column Lock" message displayed (specifically noted in TSB #20NA021 for 2020 models).
• Check Engine Light is on.
• Driver Information Center (DIC) may show a blank message box when trying to change settings, like 4x4 mode.

Most Likely Causes

1. Serial Data Gateway Module (SDGM) Logic Lock or Connector Failure 🔴 High Probability → Shop Telematics Interface Module TSB #PIT5586G specifically identifies a "logic lock" (software freeze) or poor terminal tension in the X1 and X2 connectors of the SDGM as a primary cause for U0155 on 2017-2019 K2XX models. The SDGM is a small black box, about the size of a hockey puck, located high in the driver's side footwell above the brake pedal, making its connectors sometimes vulnerable.
   How to confirm: A temporary fix for logic lock is to perform a hard reset by pulling the SDGM fuse (F26DL in the underhood fuse block for trucks) for 60 seconds. For connector issues, a technician must physically inspect the X1 (gray) and X2 (black) connectors for backed-out pins or corrosion and perform a 'pin-drag test' to check terminal tension.
   Typical fix: For a logic lock, the temporary fix is a reset, but the permanent fix is dealer reprogramming of the SDGM. For connector issues, the fix involves repairing the affected terminal or reseating the connector. In many cases, simply disconnecting and firmly reconnecting the module connectors restores communication.
   Est. part cost: $0-$150 (for terminal repair or reprogramming)
2. Weak or Failing Battery 🔴 High Probability → Shop Vehicle Battery Modern trucks have a high electrical demand with numerous modules. Low system voltage during startup is a very common cause of temporary communication glitches between modules, which can set a U0155 code.
   How to confirm: Use a multimeter to check the battery voltage with the engine off (should be ~12.4-12.6V). Perform a load test to check its health. With the engine running, check alternator output (should be ~13.5-14.5V).
   Typical fix: Recharge or replace the battery. Ensure battery terminals are clean and tight.
   Est. part cost: $150-$350
3. Faulty Instrument Panel Cluster (IPC) 🟡 Medium Probability → Shop Instrument Cluster The IPC itself can fail internally due to cracked solder joints on the circuit board from vibration and temperature changes, or failure of individual components like stepper motors that drive the needles.
   How to confirm: If the battery, fuses, and SDGM connections are confirmed good, and a professional scan tool cannot communicate directly with the IPC, the cluster itself is the likely culprit.
   Typical fix: Replacement of the Instrument Panel Cluster. The new unit must be programmed to the vehicle's VIN and mileage. Alternatively, specialized repair services can rebuild the original cluster.
   Est. part cost: $500-$800 (New OEM), $200-$400 (Rebuild Service)
4. Wiring or Connector Issue ⚪ Low Probability Connectors behind the dash or at the BCM/SDGM can become loose. Wires can chafe and short, especially if aftermarket equipment (lights, stereo, remote start) has been improperly installed.
   How to confirm: Visually inspect the connectors at the back of the IPC and at the SDGM. Check for pushed-out pins, corrosion, or wire damage. A multimeter can be used to check for continuity and shorts on the CAN bus wires (Pins 6 and 14 at the OBD-II port should show ~60 ohms of resistance with the battery disconnected).
   Typical fix: Repair the damaged wire or clean/re-seat the connector.
   Est. part cost: $10-$100

Rare But Worth Checking

• Steering Column Control Module Issue: TSB #20NA021 for 2020 models directly links a "Service Steering Column Lock" message and code U0155 to a problem requiring a specific repair procedure. While rare overall, it's a documented cause for this specific model year.
• Aftermarket Device Interference: Poorly installed remote starters, alarms, or even plug-in insurance/telematics dongles can disrupt CAN bus communication and trigger a U0155 code.
• Blown Fuse: A blown fuse for the Instrument Cluster (IPC) or Serial Data Gateway Module (SDGM) will cut power and cause an immediate communication loss. Always check fuses in the under-hood and interior fuse panels.

Diagnosis Steps

1. Check and load test the battery. Ensure system voltage is stable and above 12.4V with the engine off.
2. Use a professional scan tool to pull codes from ALL modules (BCM, ECM, SDGM, etc.), not just the engine computer. Note if other U-codes are present, which strongly suggests a network-wide issue.
3. Consult TSBs. For 2017-2019 models, review TSB #PIT5586G. For a 2020 model with a steering column message, review TSB #20NA021.
4. Attempt SDGM Reset: Locate the underhood fuse block and pull the fuse for the SDGM (F26DL for trucks) for one minute, then reinstall. This can clear a 'logic lock'.
5. Inspect SDGM Connectors: Disconnect the battery. Locate the SDGM above the driver's pedals. Carefully inspect the gray (X1) and black (X2) connectors for loose pins, corrosion, or damage. Firmly reseat them.
6. Check Fuses: Inspect all fuses related to the Instrument Panel Cluster (IPC), Body Control Module (BCM), and SDGM in both the interior and under-hood fuse panels.
7. Test CAN Bus Resistance: With the battery disconnected, use a multimeter to measure resistance between Pin 6 (CAN High) and Pin 14 (CAN Low) at the OBD-II port. A healthy network should read approximately 60 ohms.
8. If an aftermarket device is plugged into the OBD-II port or spliced into the wiring, remove it and re-test.
9. If all else fails, the issue likely lies with a faulty module (IPC or SDGM) which will require professional replacement and programming.

Parts You'll Likely Need

• Battery — Low voltage is a primary cause of network communication errors on these vehicles.
  Trusted brands: ACDelco, DieHard, Optima
  OEM price range: $200-$350
  Aftermarket price range: $150-$250
• Instrument Panel Cluster (IPC) (OEM #e.g., 84591244 (Varies significantly by trim and year)) — If the module itself fails internally, it will need to be replaced. This is a common failure point but should be diagnosed last.
  Trusted brands: ACDelco (OEM), Dorman (Remanufactured)
  OEM price range: $500-$800
  Aftermarket price range: $300-$600 (Remanufactured)
• Serial Data Gateway Module (SDGM) (OEM #e.g., 84358039 (Varies by year)) — TSB #PIT5586G identifies this module as a primary failure point for network communication issues, either through software lock-up or connector problems.

Related Codes That Often Appear With This One

• U0100, U0101, U0140, etc. — TSB #PIT5586G lists a large number of U-codes that can appear alongside U0155. This indicates a broader network problem, often pointing to the Serial Data Gateway Module (SDGM) as the source, as it acts as the central hub for communication between different CAN buses.

Technical Service Bulletins (TSBs) & Recalls

• 20NA021: Addresses a 'Service Steering Column Lock' message accompanied by U0155 on 2020 models.
• PIT5586G: Points to a logic lock or connector pin issue at the Serial Data Gateway Module (SDGM) as a cause for U0155 and a host of other communication codes on 2017-2019 models.

Platform-Specific Known Issues

• TSB #PIT5586G notes that on 2017-2019 K2XX models, a logic lock in the Serial Data Gateway Module can cause U0155 and many other communication codes. The first step is to attempt a reset by pulling the SDGM fuse. If that fails, inspection of the X1/X2 connectors for poor terminal tension is required before module replacement.
• TSB #20NA021 addresses an issue on 2020 T1XX models where an intermittent "Service Steering Column Lock" message is displayed along with code U0155, pointing to a specific repair for the steering column components rather than the IPC or SDGM.

Mechanic-Grade Diagnostic Values

• CAN Bus Network Resistance — expected: ~60 Ω (± 5 Ω) with battery disconnected, measured between Pins 6 and 14 of the OBD-II port.. Failure: A reading of ~120 Ω suggests an open circuit or a missing terminating resistor. A reading near 0 Ω indicates a short between the CAN High and Low wires.
• CAN High Voltage to Ground — expected: 2.5V to 3.0V DC with key on, engine off.. Failure: Voltage stuck near 0V or 5V, or being outside the expected range, indicates a short or open on the CAN High wire.
• CAN Low Voltage to Ground — expected: 2.5V to 2.0V DC with key on, engine off.. Failure: Voltage stuck near 0V or 5V, or being outside the expected range, indicates a short or open on the CAN Low wire.
• IPC Ground Pin Resistance to Chassis — expected: < 0.5 Ω.. Failure: High resistance indicates a corroded, loose, or otherwise poor ground connection for the instrument cluster.

Hidden / Shadow Codes Worth Checking

• U0155 as History Code in PPS: A U0155 code stored only as 'history' in the Passenger Presence System (PPS) module can be caused by a normal key-on timing difference between the PPS and the IPC. (see via This distinction is visible in the GM GDS2 scan tool when viewing codes by module. If the code is only a history event in the PPS and not active elsewhere, it can likely be disregarded for PPS diagnostics.)

Scan Tool Commands That Help

• GM GDS2: Vehicle DTC Information — Use this function first to perform a full network scan. Seeing which modules are reporting U0155 (and what other U-codes are present) helps determine if the fault is isolated to the IPC or is a widespread network issue pointing to the SDGM or a main bus wiring problem.
• GM GDS2: Module Diagnostics > IPC > Control Functions — This allows for bidirectional control of the instrument cluster. A technician can command a gauge sweep, turn on individual warning lights, or test the chimes. If the cluster responds to these commands, the cluster hardware itself is likely functional, pointing the diagnosis towards a communication or data input issue.
• GM GDS2: Module Setup / Configuration — This function is mandatory after replacing the Instrument Panel Cluster (IPC) or the Serial Data Gateway Module (SDGM). The new module must be programmed and configured to the vehicle's VIN and options to restore communication and function.

Wiring & Ground Locations

• G218 — Under the dashboard on K2XX (2017-2019 LD) models. Some sources place it on the passenger side, others on the driver's side. It is a common ground point for multiple components.. This ground is a well-documented weak point. TSB PIT5405C notes that the dash insulator mat can get trapped under the ground terminal, causing a poor connection that leads to flickering lights and communication codes like U0155.
• G110 / G114 — Main ground points for the T1XX (2019-2020) platform.. Similar to G218 on the older platform, poor connections at these primary grounds can cause widespread electrical issues, including module communication loss.
• IPC Connector — Directly at the back of the Instrument Panel Cluster, requires dash trim removal to access.. This is the final connection point for the IPC. Verifying battery voltage, ground continuity (<0.5 Ω), and CAN bus signals at this connector's pins is a critical step to confirm if the fault is in the wiring harness or the cluster itself.
• SDGM Connectors X1 (Gray) & X2 (Black) — Located on the Serial Data Gateway Module, high in the driver's side footwell above the brake pedal.. TSB #PIT5586G specifically calls out these connectors for poor terminal tension or corrosion, which directly causes U0155 and other communication codes. GM offers terminated leads (Part No. 84619127) for repairing damaged terminals in these connectors.

Real Owner Repair Stories

• CorvetteForum user (Chevrolet C8 Corvette (uses similar SDGM architecture)) — Engine would crank but not start, then started later. Over 30 communication DTCs were logged simultaneously across nearly every system.
  ❌ Tried (didn't work) Initial diagnosis was difficult due to the sheer number of codes.
  ✅ What actually fixed it The dealer eventually found the Serial Data Gateway Module (SDGM) was internally failing and replaced it, which resolved the flood of communication errors.
• YouTube video by 'Pro-Street 632' (2014-2018 Chevrolet Silverado) — Flickering dash lights, truck suddenly shutting off at low speed, loss of power steering, multiple warning lights.
  ❌ Tried (didn't work) Testing the battery and alternator, which both checked out as good.
  ✅ What actually fixed it The problem was a poor ground connection on the passenger side of the engine block. Cleaning the contact point for the ground wire and re-securing it resolved the electrical issues.

"I Checked Everything" — The Actual Cause

• A critical diagnostic trap for network codes like U0155 is relying solely on the CAN bus resistance test at the OBD-II port. A technician can measure a perfect 60 ohms (indicating the two main terminating resistors are present) yet still have a communication failure. This happens if there is an open circuit on a 'branch' of the network that goes to the Instrument Panel Cluster. The main bus remains intact, but the IPC is completely cut off. Diagnosis must include checking for signal activity directly at the module connector, not just at the OBD-II port.

Model Year Variations Within This Range

• 2017-2019 (K2XX): These models are known for issues with ground point G218 under the dash and are the primary focus of TSB #PIT5586G regarding the SDGM connectors.
• 2019-2020 (T1XX): These models use different primary ground locations, such as G110 and G114. The 2020 model specifically is covered by TSB #20NA021, which links U0155 to a 'Service Steering Column Lock' message.