U0151 on 2015-2019 GMC Sierra 2500: Lost Communication With Airbag Module Causes & Fixes

What's Unique About the 2015-2019 Gmc SIERRA 2500

For this specific generation of GMC Sierra (K2XX platform), the U0151 code is very frequently caused by one of two well-documented issues. The first is a wiring harness that gets pinched behind the instrument panel during factory assembly, a problem so common that GM issued a Technical Service Bulletin (TSB #PIT5288H) for it. The second is a software or hardware fault in the Serial Data Gateway Module (SDGM), which acts as the central router for all module communications. These two issues are far more common than the actual airbag module (SDM) failing, and diagnosis should always start with them.

Diagnostic Flowchart

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

Symptoms You May Notice

• Airbag warning light is continuously illuminated on the instrument panel.
• "Service Safety Restraint System" or "Service Airbag" message on the Driver Information Center (DIC).
• In some cases, other communication codes may be present, causing other warning lights (like Stabilitrak) or system malfunctions such as no audio, blank radio display, or inoperative steering wheel controls.
• An audible chime may sound when the ignition is turned on.
🎬 See a breakdown of U0151 symptoms and common diagnostic steps.

Most Likely Causes

1. Pinched or Damaged Instrument Panel (I/P) Wiring Harness 🔴 High Probability TSB #PIT5288H specifically identifies that the main I/P harness can get pinched between a metal dash mounting bracket and the body, near the parking brake pedal assembly. 🎬 Watch: How to find and repair this pinched wiring harness. This happens during factory assembly and can chafe through the insulation of critical CAN bus wires.
   How to confirm: Remove the driver's side dash end panel (fuse panel cover). From underneath the dash, visually and physically inspect the large harness for signs of being crushed, chafed, or damaged where it passes the metal bracket. The TSB notes it can be hard to see, but a key check is to see if the harness can be moved freely; if it is tight against the bracket, it is likely pinched.
   Typical fix: Loosen the I/P bracket mounting bolts, free the harness, and carefully open the loom to inspect individual wires. Repair any damaged wires by splicing, soldering, and heat-shrinking. Reroute the harness to prevent future contact and secure it with a zip tie.
   Est. part cost: $5-$25 for wire repair supplies like Tesa tape, solder, and heat shrink.
2. Serial Data Gateway Module (SDGM) Logic Lock or Failure 🟡 Medium Probability TSB #20-NA-212 (which supersedes #PIT5586E) notes that the SDGM can enter a 'logic lock' state where it powers up but fails to communicate, causing multiple U-codes, including U0151. It can also be caused by bent or loose terminals in the SDGM connectors.
   How to confirm: This is best confirmed with a professional scan tool. If multiple modules across different networks are losing communication simultaneously, the SDGM is a prime suspect. A technician can inspect the X1 and X2 connectors at the SDGM (located behind the glove box) for backed-out or damaged pins.
   Typical fix: First, attempt a 'hard reset' by disconnecting the battery for 30 minutes. If that fails, a dealer or qualified shop may need to reprogram the SDGM with updated software per TSB #20-NA-212. If reprogramming fails or pins are damaged, the module itself requires replacement and programming.
   Est. part cost: $150-$350 for a new SDGM.
3. High Resistance in Communication Enable Circuit (5986) ⚪ Low Probability TSB #PIT5457D describes how an open or high resistance in the 'wake-up' circuit from the BCM can prevent modules like the SDM from turning on to communicate. This can be caused by corrosion under the driver's or passenger's sill plates.
   How to confirm: Using a multimeter, check for approximately 12 volts on the communication enable circuit (Circuit 5986, typically a Pink wire) at the SDM connector with the ignition on. The circuit should be able to light a small test bulb (like a 194 bulb), but not a heavy load like a headlight. A 194 bulb draws about 250mA; if voltage drops below 11V with this load, high resistance is present in the circuit.
   Typical fix: Trace the circuit back to the BCM, inspecting for opens, shorts, or high resistance at connectors and splice points, particularly under the door sill plates where corrosion is common. Repair the wiring as needed.
   Est. part cost: $5-$25 for wire repair supplies.
4. Faulty Sensing and Diagnostic Module (SDM) ⚪ Low Probability While possible, outright failure of the SDM is less common than the wiring and gateway module issues on this platform. Sometimes the module can get into a logic lock state after a voltage fluctuation, which can be resolved without replacement.
   How to confirm: This is a process of elimination. If power, ground, and the CAN bus network wiring to the SDM are all verified to be good, and the SDGM is functioning correctly, the SDM itself is likely faulty. A temporary fix can sometimes be achieved by pulling the SDM fuse for 30-60 seconds to reset it.
   Typical fix: Replace the Sensing and Diagnostic Module. This new module MUST be programmed to the vehicle's VIN by a dealer or a properly equipped independent shop using GDS2 software. The SDM is typically located under the center console or front center of the cab.
   Est. part cost: $300-$600 for a new SDM.

Rare But Worth Checking

• Corroded underhood fuse block connections. Moisture can get into the fuse block, causing corrosion on the fuse terminals for the SDM, leading to high resistance.
• Poor ground connections. A bad chassis ground (like G218) can cause a wide range of communication issues.

Diagnosis Steps

1. Perform a full vehicle scan to see which other modules, if any, are reporting communication loss codes. A long list of 'U' codes points towards a network problem (SDGM or wiring).
2. Check the fuses for the SDM/Airbag system in both the underhood and instrument panel fuse blocks. Inspect for corrosion, not just if the fuse is blown.
3. Following TSB #PIT5288H, remove the driver's side dash end cap and thoroughly inspect the wiring harness for pinching or damage near the metal I/P mounting bracket by the parking brake. Check if the harness is tight or can move freely.
4. If the harness looks good, disconnect the battery for at least 30 minutes to perform a hard reset, which may clear a logic lock in the SDGM. Alternatively, try pulling the dedicated SDM fuse for 60 seconds.
5. If the code persists, use a multimeter to verify good power (12V+) and ground at the SDM connector. The SDM is often located under the front center of the cab or center console.
6. Check the CAN bus wiring at the SDM connector for proper resistance (should be ~60 ohms between CAN High and CAN Low with the battery disconnected) and for shorts to power or ground.
7. If wiring, power, and grounds are all good, the issue likely lies with the SDGM (especially if other U-codes are present) or the SDM itself (if U0151 is the only code). SDGM inspection/reprogramming or SDM replacement is the next step.

Parts You'll Likely Need

• Serial Data Gateway Module (SDGM) (OEM #85073617 (supersedes 23104453, 23114650, 23337305; always verify with VIN)) — This module can enter a 'logic lock' state or fail, causing widespread communication codes, including U0151, as noted in TSB #20-NA-212.
  Trusted brands: ACDelco (Genuine GM)
  OEM price range: $150-$350
  Aftermarket price range: $150-$250
• Sensing and Diagnostic Module (SDM) (OEM #13518054 (always verify with VIN)) — Though less common, the SDM can fail internally. It is the last part to be replaced after all wiring, grounds, and other network modules have been verified as good.
  Trusted brands: ACDelco (Genuine GM)
  OEM price range: $300-$600
  Aftermarket price range: Not Recommended

Related Codes That Often Appear With This One

• U0140 — Lost Communication with Body Control Module. Often appears with U0151 when a network-wide issue like a faulty SDGM or major wiring problem is the cause.
• U0073 — Control Module Communication Bus 'A' Off. This indicates a general failure of the high-speed CAN bus, often pointing to the SDGM or a short in the main harness.
• U0126 — Lost Communication With Steering Angle Sensor Module. This code is specifically mentioned in TSB #PIT5288H as a possible companion code when the instrument panel harness is pinched.
• U0077 — Lost Communication with another specific module. This code is also listed in TSB #PIT5288H and points to the pinched harness affecting multiple systems.

Technical Service Bulletins (TSBs) & Recalls

• PIT5288H
• 20-NA-212
• PIT5586E
• PIT5457D

Platform-Specific Known Issues

• TSB #PIT5288H: This is the most critical document for this code on this truck. It details how the instrument panel wire harness can be pinched between a dash mounting bracket and the body, causing U0151 and a host of other seemingly unrelated electrical issues. The fix involves freeing the harness and repairing damaged wires.
• TSB #20-NA-212 (supersedes PIT5586E): This bulletin addresses multiple communication DTCs, including U0151, that can be caused by a logic lock or internal fault in the Serial Data Gateway Module (SDGM). The first recommended step is reprogramming the module; if that fails, inspection of connector pins and potential module replacement is required.

Mechanic-Grade Diagnostic Values

• High-Speed CAN Bus Network Resistance — expected: Approximately 60 Ohms (± 5 Ohms). Failure: A reading of 120 Ohms indicates an open circuit or a missing terminating resistor. A reading significantly less than 60 Ohms (e.g., near 0 Ohms) indicates a short between the CAN High and CAN Low wires.
• Communication Enable Circuit (5986) Voltage — expected: Approximately 12 Volts with key on, engine off.. Failure: Low or no voltage indicates an open or short in the circuit. When load tested with a 194 bulb (~250mA), the voltage should not drop below 11 volts; a larger drop indicates high resistance.
• Ground Circuit Resistance — expected: Less than 0.1 Ohms.. Failure: A reading higher than 0.1 Ohms indicates a poor ground connection, which can cause intermittent communication issues.

Scan Tool Commands That Help

• GDS2 (Global Diagnostic System 2): Configure New Module / Setup SDM Part Number in BCM — This function is mandatory after replacing the Sensing and Diagnostic Module (SDM). It programs the new module to the vehicle's VIN and configures it within the BCM and greater vehicle network. Failure to perform this step will result in the airbag light staying on and the new module not functioning.
• GDS2 (Global Diagnostic System 2): Enable Deployment Loops — This is part of the final setup procedure after a new SDM is installed and programmed. It confirms all airbag components are connected and ready. If this step fails, it indicates an issue elsewhere in the SRS system (like a disconnected pretensioner) that is preventing the SDM from fully initializing.
• GDS2 (Global Diagnostic System 2): Clear All DTCs — After a repair (like fixing a pinched harness or replacing a module), this command should be used to clear the U0151 code. The airbag system will perform a self-test upon the next ignition cycle to confirm the fault is resolved.

Wiring & Ground Locations

• SDM (Sensing and Diagnostic Module) — Typically located under the center console or under the front seats, bolted directly to the cab floor.. This is the module that has lost communication. All power, ground, and communication wires terminate here, making its connector a critical test point.
• SDGM (Serial Data Gateway Module) — Located high in the dashboard, typically behind the glove box.. This module acts as a network router. A fault here can cut off communication to the SDM, causing U0151. Its X1 and X2 connectors are known weak points.
• G218 Ground — Located on the driver's side A-pillar, behind the dash trim panel, near the speaker.. This is a major ground point for many interior modules, including the BCM. TSB PIT5405C notes that sound-deadening material can get trapped under the ground lug during assembly, causing a poor connection and a host of communication DTCs.
• Pinched Harness Location — The main instrument panel harness where it passes the large, metal I/P mounting bracket near the parking brake assembly on the driver's side.. This is the specific location identified in TSB #PIT5288H as the most common cause of chafing and shorting of the CAN bus wires that lead to the U0151 code.
• Sill Plate Harnesses — Under the plastic door sill plates on both the driver's and passenger's sides.. TSB #PIT5457D identifies these areas as common locations for corrosion and damage to the Communication Enable Circuit (5986), which can prevent the SDM from waking up.

Real Owner Repair Stories

• Reddit user @boyloyall110 (2017 GMC Sierra) — U0151 code, Service Tire Monitor System message, and keyless entry not working.
  ❌ Tried (didn't work) Replacing the aftermarket grille shutter, which temporarily cleared the code.
  ✅ What actually fixed it The user noted that for the TPMS and key fob issue, a common cause is a frayed wire in the harness under the driver's side door sill plate. This harness contains wiring for the Remote Door Lock Receiver module, which handles RF signals for both the key fob and tire pressure sensors. While not explicitly stating this fixed the U0151, the location is a known problem area for multiple communication issues per TSBs.

OEM Part Supersession History

• 23104453, 23114650, 23337305 → 85073617 — Standard part evolution for design, material, or technology updates by the manufacturer.
  Heads up: The part listed (85073617) is often described as a 'Trailer Brake Control Module' but functions as the Serial Data Gateway Module in many parts catalogs for this platform. Always verify the correct part for the specific vehicle VIN, as module function and naming can be confusing.