U0073 on 2015-2017 GMC Sierra: Causes and Fixes for Communication Bus Failure

What's Unique About the 2015-2017 Gmc SIERRA

On this generation of Sierra (and its K2XX platform mates), many communication issues are traced back to a central hub called the Serial Data Gateway Module (SDGM). Manufacturer service bulletins specifically point to this module and its connectors as a potential cause for a widespread network shutdown that triggers U0073 along with many other codes. Additionally, a specific ground point (G218) under the driver's dash is a well-documented weak point that can cause intermittent network loss when it fails. TSB PIT5405C explicitly details 🎬 Watch: How to locate and repair the G218 ground terminal. how insulation getting caught under the G218 ground terminal from the factory is a primary cause for this code and the associated symptoms.

Diagnostic Flowchart

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

Symptoms You May Notice

• Multiple warning lights on the instrument cluster (Check Engine, ABS, Stabilitrak, Airbag).
• Gauges fluctuating or dropping to zero, or the entire instrument cluster going blank.
• "Service Stabilitrak," "Service Power Steering," or similar messages on the driver information center.
• Engine may not crank or start.
• Engine starts and then immediately stalls.
• Transmission may shift harshly or be stuck in one gear (limp mode).
• HVAC controls are inoperative.
• Wipers operate erratically or do not park correctly.
• Radio or infotainment display is blank or unresponsive.
• Inability for a standard scan tool to communicate with some or all modules.
• Steering wheel jerks or kicks back when turning at low speeds.

Most Likely Causes

1. Poor Ground Connection at G218 🔴 High Probability This specific ground point, located under the driver's side dash near the kick panel, is a known issue. TSB PIT5405C confirms that factory insulation can get trapped under the ground terminal, preventing a solid connection and causing intermittent network failures, especially when electrical load increases (like turning the steering wheel).
   How to confirm: Visually inspect the G218 ground stud, found by removing the driver's side kick panel. Look for the black dash insulator mat caught between the metal wire eyelet and the chassis stud. A voltage drop test from the ground terminal to the negative battery post under load will confirm a bad ground (>200mV is a problem).
   Typical fix: Remove the nut, pull back the wire terminal, and cut away the section of the dash insulator mat that is interfering with the connection. Clean the wire terminal and the chassis mating surface with a wire brush or sandpaper, and securely re-fasten the ground nut.
   Est. part cost: $0 - $5
2. Faulty Serial Data Gateway Module (SDGM) 🟡 Medium Probability → Shop Telematics Interface Module The SDGM acts as a central router for network traffic. GM Technical Service Bulletin PIT5586B identifies that the SDGM can suffer from internal microcontroller errors ('logic lock') or have issues with its connector terminals, causing it to stop communicating and bringing down the entire network.
   How to confirm: This is difficult to confirm without a dealer-level scan tool. A technician would first rule out all wiring and power/ground issues. If the SDGM has proper power and ground but is not communicating, it is suspect. Sometimes, disconnecting the battery for 30 minutes can perform a 'hard reset' and temporarily restore function, which points to an SDGM logic lock.
   Typical fix: First, attempt reprogramming the SDGM with updated software via a GM dealer or a qualified shop with a subscription to GM's SPS (Service Programming System). If reprogramming fails or the module is internally shorted, it must be replaced. A new module will also require programming to the vehicle's VIN.
   Est. part cost: $80 - $250
3. Chafed or Damaged CAN Bus Wiring 🟡 Medium Probability The CAN bus wiring harness runs throughout the vehicle. Common problem areas on this platform include the wiring near the sharp metal bracket of the parking brake mechanism, under the driver's door sill plate, and where the harness passes through the firewall. Vibration and rubbing can wear through the insulation, causing the twisted pair of CAN wires to short to ground or to each other.
   How to confirm: A thorough visual inspection of the harness in known problem areas is the first step. To confirm a short, a multimeter can be used to check resistance between the CAN High and CAN Low wires (pins 6 and 14 at the OBD-II port). With the battery disconnected, resistance should be ~60 ohms. A reading of 120 ohms indicates an open circuit, and 0 ohms indicates a short between the wires.
   Typical fix: Repair the damaged section of wire. This involves cutting out the damaged portion, splicing in a new piece of wire of the same gauge using solder and heat shrink (or high-quality butt connectors), and protecting the repair with convoluted loom or high-quality electrical tape to prevent a recurrence.
   Est. part cost: $5 - $25
4. Weak or Failing Battery / Alternator ⚪ Low Probability → Shop Vehicle Battery Modern control modules are sensitive to voltage. If battery voltage drops significantly during startup (below 12.0V), modules can fail to initialize correctly, causing them to drop off the communication network and trigger a U0073 code. This is often an intermittent issue, occurring more frequently in cold weather.
   How to confirm: Test the battery with a digital multimeter. A healthy, fully charged battery should read above 12.4V with the engine off. With the engine running, the alternator should be charging between 13.7V and 14.7V. A load test is the most definitive way to confirm battery health, as a battery can show good voltage but fail under load.
   Typical fix: Replace the weak battery or faulty alternator.
   Est. part cost: $150 - $600

Rare But Worth Checking

• Blown 175-Amp Mega Fuse: This is most common after an improper jump-start. A voltage spike can blow this main fuse, which is located in the battery distribution block. This will cut power to multiple modules, taking the network offline.
• Faulty Terminating Resistor: The CAN bus has two 120-ohm resistors at each end of the network. If one fails, the network integrity is compromised, and resistance will read 120 ohms instead of the correct 60 ohms. These resistors are often located inside a control module (like the ECM or Instrument Panel Cluster), so diagnosing this usually requires isolating modules one by one.
• Single Faulty Module: Less commonly, a single module (like the ABS or instrument panel cluster) can fail internally and short out the entire network by 'chattering' or sending corrupt data. This is usually diagnosed by unplugging modules one at a time until communication is restored to the others, a process made easier with a breakout box.
• Poor Connection at Starter Solenoid: TSB PIT5405C also notes that the B+ battery cable terminal at the starter can be mis-installed or the starter heat shield can come loose, causing a short to the terminal. This creates a massive voltage drop across the electrical system, triggering network codes.

Diagnosis Steps

1. Check and charge the battery. Ensure voltage is above 12.4V and have it load tested. Clean battery terminals and verify main cable connections are tight.
2. Use a high-quality scan tool to pull codes from ALL modules. Note which modules are not communicating.
3. Locate and inspect the G218 ground point under the driver's side dash, near the A-pillar/kick panel. Check for tightness and for the dash insulator mat being trapped under the terminal. Correct as needed per TSB PIT5405C.
4. Visually inspect the wiring harness for chafing or damage, especially near the parking brake pedal mechanism, under the driver's seat, and at the firewall pass-through.
5. Disconnect the battery. At the OBD-II port, measure the resistance between Pin 6 (CAN High) and Pin 14 (CAN Low). The reading should be approximately 60 ohms. A reading of 120 ohms indicates an open in the circuit or a faulty terminating resistor.

Parts You'll Likely Need

• Serial Data Gateway Module (SDGM) — This module is a central communication hub and is cited in GM TSBs as a primary cause of network failure.
  Trusted brands: ACDelco
  OEM price range: $150-$300
  Aftermarket price range: $100-$200
• Wiring Repair Supplies — If the cause is a chafed or broken wire, you will need wire, butt connectors or solder, heat shrink tubing, and wire loom to perform a durable repair.
  OEM price range: $5-$25
  Aftermarket price range: $5-$25

Related Codes That Often Appear With This One

• U0100 — Lost Communication With Engine Control Module (ECM).
• U0101 — Lost Communication with Transmission Control Module (TCM).
• U0121 — Lost Communication With Anti-Lock Brake System (ABS) Control Module.
• U0140 — Lost Communication With Body Control Module (BCM).
• U0155 — Lost Communication With Instrument Panel Cluster (IPC) Control Module

Technical Service Bulletins (TSBs) & Recalls

• PIT5586B: Addresses various communication DTCs, including U0073, pointing to the Serial Data Gateway Module (SDGM) as a potential cause.
• PIT5405C: Details numerous electrical issues (Stabilitrak, blank screens, no start) and a long list of U-codes including U0073, citing the G218 ground fault, battery cable issues, and starter solenoid shorts as primary causes.

Platform-Specific Known Issues

• TSB #PIT5586B points to the Serial Data Gateway Module (SDGM) as a potential cause for a host of communication DTCs, including U0073, and instructs technicians to check its connectors.
• TSB #PIT5405C also lists U0073 in a group of codes that can be set due to communication issues, manifesting as erratic wiper behavior.
• TSB #20-NA-212 (which supersedes PIT5586E) further details that an SDGM microcontroller error can cause it to stop communicating on all CAN channels, or that its connector terminals can be bent or loose.
• TSB #PIT4730B warns that an intermittent short on the high-speed CAN bus can cause the BCM to appear offline, triggering code U0073, and advises against prematurely replacing the BCM.

Mechanic-Grade Diagnostic Values

• CAN Bus Resistance (Battery Disconnected) — expected: ~60 Ω (measured between Pin 6 and Pin 14 of the OBD-II port). Failure: A reading of ~120 Ω indicates an open circuit or a failed terminating resistor. A reading near 0 Ω indicates a short between the CAN High and CAN Low wires.
• CAN Bus Voltage (Recessive State, Key On) — expected: ~2.5 V on both CAN High (Pin 6) and CAN Low (Pin 14) to ground. Failure: Significant deviation from 2.5V on either line indicates a potential short to power or ground.
• CAN Bus Voltage (Dominant State, Data Transmitting) — expected: CAN High: ~3.5 V, CAN Low: ~1.5 V (requires an oscilloscope to view). Failure: Inability for the bus lines to be pulled to these approximate voltages indicates a bus health problem.
• Battery & Charging System Voltage — expected: >12.4 V (engine off), 13.7 V - 14.7 V (engine running). Failure: Low static voltage or improper charging voltage can cause modules to drop off the network intermittently.

Hidden / Shadow Codes Worth Checking

• U0073 71: Control Module Communication Bus Off - Invalid Data Received. This indicates the network is physically working but one module is sending corrupt information. (see via A dealer-level scan tool like the GM GDS2 is required to see these specific 2-digit symptom codes.)
• U0073 72: Control Module Communication Bus Off - Alive Counter Incorrect. This suggests a module is not checking in with the network at the expected interval, often due to a software or internal module fault. (see via A dealer-level scan tool like the GM GDS2 is required to see these specific 2-digit symptom codes.)

Scan Tool Commands That Help

• GM GDS2 (or equivalent high-end scan tool): Module Communication Status / Vehicle Wide DTC Check — This should be the first step. It provides a complete list of all modules on the vehicle and shows which ones are actively communicating and which are offline. This helps narrow down the location of the fault.
• GM GDS2: Data Bus Diagnostic Tool — This is a guided diagnostic routine within the GM service software. It systematically walks a technician through tests to diagnose High Speed LAN (CAN bus) issues, making it useful after the initial module status check.
• GM SPS (Service Programming System): SDGM Programming and Setup — This is required after replacing the Serial Data Gateway Module (SDGM). The new module must be programmed with the vehicle's VIN and configuration data to function.

Wiring & Ground Locations

• G218 — Under the driver's side dash, bolted to the A-pillar frame, usually behind the kick panel.. This is the most common cause for U0073 on this platform. The factory dash insulation mat often gets trapped under the ground terminal, causing a poor, intermittent connection that takes down the entire communication network.
• External Terminating Resistor — Taped to the main wiring harness, typically located in the rear of the vehicle above the spare tire and muffler area.. The CAN bus requires two 120-ohm resistors. One is in the ECM, and the other is this external one. If this resistor or its wiring fails, the bus resistance becomes 120 ohms instead of the required 60 ohms, causing communication to fail.
• X225 Connector — Behind the lower left side of the instrument panel, in the passenger compartment.. A GM Technical Service Bulletin (PIT5277A) points to this connector as a potential location for bent or backed-out terminals, which can cause an open in the CAN bus circuit.
• Parking Brake Chafe Point — The wiring harness that runs near the metal bracket of the parking brake pedal assembly under the driver's dash.. The sharp edges of the parking brake bracket can rub through the insulation of the CAN bus wires over time, causing them to short to ground or to each other.

Real Owner Repair Stories

• silveradosierra.com forum user (2007.5 Chevrolet Silverado 2500HD) — Service Stabilitrak, Service Trailer Brake, Check Engine lights on. Codes U0073, U0100, U0101, U0121, U0140.
  ❌ Tried (didn't work) Initial diagnosis was unclear.
  ✅ What actually fixed it The problem was a faulty Trailer Brake Control Module (TBCM). Unplugging the TBCM allowed all other modules to communicate again. The TBCM contained a faulty terminating resistor which brought down the entire bus.
• Forum user report (2008 Chevrolet Silverado) — Multiple warning lights, loss of communication with several modules.
  ❌ Tried (didn't work) Checking fuses, Inspecting visible wiring in the engine bay
  ✅ What actually fixed it Found a corroded connector located under the driver's seat, attached to the frame rail. Cleaning the terminals within this connector restored network communication.

OEM Part Supersession History

• 13518851, 13524378, 13524379, 13532121 → 13534928 — Internal revisions for improved reliability and to address logic lock issues.
  Heads up: While the newer part number is generally backward compatible, any replacement SDGM requires vehicle-specific programming using GM's Service Programming System (SPS) to function.