U0073 on 2015-2017 Chevrolet Silverado: Causes and Fixes for Communication Bus 'A' Off

What's Unique About the 2015-2017 Chevrolet SILVERADO

On this generation of Silverado (K2XX), GM uses a Serial Data Gateway Module (SDGM) as a central traffic controller for the various data networks. As highlighted in Technical Service Bulletin #PIT5586B, this specific module can experience a 'logic lock' or internal failure, becoming a central point of failure and causing a U0073 code. Other highly common issues on this platform include a poor BCM ground (G218) under the driver's side dash where an insulation mat interferes with the connection, and specific wiring chafe points near the park brake pedal.

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 dashboard (Check Engine, ABS, StabiliTrak, Service Power Steering).
• Loss of power steering assist, sometimes intermittently.
• Engine may stall or not start.
• Transmission may shift erratically or get stuck in one gear.
• HVAC controls may be inoperative. [TSB #PIT5586B]
• Wipers may run continuously or park in the wrong position. [TSB #PIT5405C]
• Instrument cluster gauges may freeze, show dashes, or go blank.
• Reduced engine power or 'limp mode'.
• Radio or infotainment screen is blank or frozen.

Most Likely Causes

1. Poor Ground Connection (G218) 🔴 High Probability A widely documented issue involves the main BCM ground (G218), located under the driver's side A-pillar/kick panel area. The dash insulator mat often gets trapped under the ground terminal during assembly, causing a poor, intermittent connection that worsens over time.
   How to confirm: Locate G218 behind the driver's side kick panel. Remove the 10mm nut, pull the ground terminal away, and check if the black foam insulation is caught underneath it. A visual inspection often confirms the fault. 🎬 Watch: How to find and fix the G218 ground issue. A voltage drop test from the battery negative post to the ground stud will show high resistance if the connection is poor.
   Typical fix: Remove the nut, cut or trim away the interfering foam insulation mat, clean the ground terminal and the stud to bare metal, apply dielectric grease, and re-secure the nut tightly.
   Est. part cost: $0 - $5
2. Wiring Harness Damage 🟡 Medium Probability Known chafe points exist near the parking brake mechanism and under the driver's seat carpet where the harness can rub through. Additionally, TSB #18-NA-114 notes that the engine harness can chafe against the G100 ground stud, potentially damaging CAN bus wires.
   How to confirm: Visually inspect the wiring harness in common chafe locations. With the battery disconnected, measure the resistance between Pin 6 (CAN High) and Pin 14 (CAN Low) at the OBD-II port. A reading of ~60 ohms is normal; 120 ohms indicates a break in the wiring, and near 0 ohms indicates a short.
   Typical fix: Repair the damaged wires by soldering and protecting them with heat-shrink tubing and woven electrical tape. Reroute the harness slightly to prevent future contact.
   Est. part cost: $5-$20
3. Failed Serial Data Gateway Module (SDGM) 🟡 Medium Probability TSB #PIT5586B directly identifies the SDGM as a potential cause for U0073. The module can suffer from a 'logic lock' (freeze) or internal failure, taking down all networks it controls.
   How to confirm: This is often diagnosed by elimination. If wiring and grounds are good, the SDGM is a prime suspect. A temporary fix can sometimes be achieved by disconnecting the battery for 30 minutes to reset the modules. If communication returns, the SDGM is likely failing. A professional scan tool can also show if the SDGM is offline.
   Typical fix: Replace the Serial Data Gateway Module. This may require programming by a dealer or a qualified shop with access to GM's software.
   Est. part cost: $80-$150
4. Weak or Failing Battery ⚪ Low Probability
   How to confirm: Test the battery voltage with a multimeter. It should be above 12.4V with the engine off and 13.7-14.7V when running. A simple voltage test is not enough; a load test is the most definitive way to confirm battery health, as low voltage during startup is a common trigger.
   Typical fix: Charge or replace the battery.
   Est. part cost: $150-$300
5. Faulty Aftermarket Electronics ⚪ Low Probability
   How to confirm: If a remote starter, alarm, trailer brake controller, or other device was installed, temporarily disconnect it completely from the vehicle's wiring and see if communication is restored. Improperly installed devices can interfere with or short the CAN bus.
   Typical fix: Remove the faulty device or have it professionally re-installed.
   Est. part cost: $0

Rare But Worth Checking

• Blown 175-Amp Mega Fuse: This can occur after an improper jump-start (reversed polarity or voltage spike). This fuse is located on the battery distribution block and protects major modules. Forum users have reported this exact failure scenario leading to a completely dead truck and U0073.
🎬 See how a blown mega fuse causes these electrical symptoms.
• Failed Terminating Resistor: The CAN bus has two 120-ohm resistors wired in parallel, creating the normal 60-ohm network resistance. One is internal to the ECM. The second is often internal to another key module like the SDGM or located in a resistor pack near the rear of the vehicle. If this external resistor or its wiring fails, the network resistance will jump to 120 ohms, causing communication instability.
• Corroded Frame Rail Connector: A user on gm-trucks.com with a similar platform truck fixed multiple 'U' codes, including U0073, by finding and cleaning a corroded multi-wire connector located on the frame rail under the driver's seat. Water and road salt can compromise these connections over time.

Diagnosis Steps

1. Check the battery and charging system. Ensure voltage is stable and above 12.4 volts engine-off, and that it passes a load test.
2. Scan all modules for codes. Use a high-quality scanner to see which modules are not communicating. This is a critical clue.
3. Disconnect any aftermarket accessories (remote start, aftermarket radio, trailer brake controller) to eliminate them as a cause.
4. Crucial Step: Inspect and clean the BCM ground G218. Locate it in the driver-side kick panel area, remove the nut, and trim back any interfering foam insulation before cleaning and retightening.
5. Perform a thorough visual inspection of the main wiring harnesses, especially around the driver's side kick panel, under the driver's seat, and near the parking brake assembly for any signs of chafing or damage.
6. Inspect the engine harness for chafing near the G100 ground stud, as per TSB #18-NA-114.
7. With the battery disconnected, use a multimeter to measure the resistance between Pin 6 and Pin 14 of the OBD-II diagnostic port. A healthy network will read approximately 60 Ohms.
🎬 Watch: Step-by-step guide to diagnosing the U0073 communication code.
8. If the resistance is 120 Ohms, it indicates an open circuit, likely a broken wire or a failed terminating resistor. If it's near 0 Ohms, there is a short between the two CAN wires.
9. If the wiring and grounds are good, the Serial Data Gateway Module (SDGM) is the next most likely suspect, as per TSB #PIT5586B.

Parts You'll Likely Need

• Serial Data Gateway Module (OEM #13533490) — This module is a known failure point on this platform that can 'freeze' or fail, taking down the entire communication network, as cited in GM Technical Service Bulletin PIT5586B. Part number is subject to supersession.
  Trusted brands: ACDelco, GM Genuine Parts
  OEM price range: $80-$150
  Aftermarket price range: $60-$120

Related Codes That Often Appear With This One

• U0100 — Lost Communication With ECM/PCM
• U0101 — Lost Communication with TCM
• U0121 — Lost Communication With Electronic Brake Control Module
• U0140 — Lost Communication With Body Control Module
• U0155 — Lost Communication With Instrument Panel Cluster (IPC) Control Module

Technical Service Bulletins (TSBs) & Recalls

• PIT5586B: Addresses multiple communication DTCs and symptoms like inoperative HVAC, pointing towards the Serial Data Gateway Module.
• PIT5405C: Connects erratic wiper behavior with DTC U0073 and other communication codes, often related to the G218 ground.
• 18-NA-114: Warns of engine harness chafing against the G100 ground stud causing various DTCs including U0073.

Platform-Specific Known Issues

• TSB #PIT5586B: Mentions that various issues, including inoperative HVAC controls and no-start conditions, can be caused by a network failure involving multiple 'U' codes. The bulletin instructs technicians to investigate the Serial Data Gateway Module (SDGM) in these cases.
• TSB #PIT5405C: Links intermittent wiper operation and a host of communication codes, including U0073, to potential electrical issues like a poor G218 ground or a faulty battery.

Mechanic-Grade Diagnostic Values

• High-Speed GMLAN Bus Resistance — expected: Approximately 60 Ω (Ohms) when measured between Pin 6 and Pin 14 of the OBD-II port with the battery disconnected.. Failure: A reading of ~120 Ω indicates an open circuit or a failed terminating resistor. A reading near 0 Ω indicates the CAN High and Low wires are shorted together.
• CAN High Voltage to Ground — expected: Fluctuating between 2.5V and 3.5V with the key on.. Failure: Voltage that is stuck high, low, or does not fluctuate indicates a bus problem.
• CAN Low Voltage to Ground — expected: Fluctuating between 2.5V and 1.5V with the key on.. Failure: Voltage that is stuck high, low, or does not fluctuate indicates a bus problem.
• G218 Ground Voltage Drop — expected: Less than 0.1V (100mV) when measured between the ground stud and the negative battery terminal with the ignition on and high electrical load.. Failure: A voltage reading significantly higher than 0.1V confirms a high-resistance ground connection that needs to be cleaned.

Scan Tool Commands That Help

• GM GDS2 (Global Diagnostic System 2): Data Bus Diagnostic Tool — This function, included with GDS2, actively queries the CAN bus to create a list of which modules are responding and which are not. It helps a technician quickly identify the scope of the communication failure and pinpoint which modules are offline, providing a starting point for diagnosis.
• GM GDS2 (Global Diagnostic System 2): Vehicle DTC Information — This command scans all modules on the vehicle and presents a comprehensive list of which ones have stored codes. For a U0073 fault, this helps determine if the issue is system-wide (many modules reporting lost communication) or isolated to a specific branch of the network.
• GM GDS2 (Global Diagnostic System 2): Clear All DTCs / Global Power Reset — After a physical repair (like fixing a ground or replacing a fuse), modules can remain in a 'logic lock' state. Using the scan tool to clear all codes, or performing a manual global reset by disconnecting the battery and touching the cable ends together, forces all modules to reboot and re-establish communication.

Wiring & Ground Locations

• G218 — Behind the driver's side kick panel, near the A-pillar. A 10mm nut secures one or more ground eyelets to a stud.. This is the primary ground for the Body Control Module (BCM). A poor connection here, often caused by an interfering foam insulator, is the most common cause of U0073 and related network issues on this platform.
• Serial Data Gateway Module (SDGM) — Under the driver's side dash, typically above the heating/AC vent that directs air to the footwell.. This module is the central hub for network traffic. A failure here can bring down the entire High-Speed CAN bus. TSB #PIT5586B specifically points to this module as a cause. Its connectors are a key test point.
• SDGM Black Connector (X3) — The far-left connector on the Serial Data Gateway Module.. This connector contains the High-Speed CAN bus wires (Pins 5 & 6, Blue and White). It's a primary location for checking bus voltages or performing circuit tests when diagnosing a U0073 code.
• Terminating Resistors — There are two 120-ohm resistors. One is internal to the Engine Control Module (ECM). The other is typically at the opposite end of the bus, often within the Serial Data Gateway Module (SDGM) or a separate resistor pack.. The network requires both resistors to be present to function, creating a total resistance of 60 ohms. If a wire breaks or a module containing a resistor fails, the resistance will jump to 120 ohms, causing communication to stop.
• 175-Amp Mega Fuse — On the battery positive distribution block, under a red plastic cover directly on or next to the battery.. This main fuse protects multiple critical modules. It can blow from a voltage spike during an improper jump-start, causing a total loss of communication (U0073) and a no-start condition.

Real Owner Repair Stories

• YouTube diagnostic video (2017 Chevrolet Silverado) — Intermittent no-start, gauges dropping out, loss of RPM and oil pressure readings, loss of power steering, multiple communication codes.
  ❌ Tried (didn't work) Initial scan showed no communication with ECM and TCM.
  ✅ What actually fixed it The primary fault was found to be faulty butt connectors from a previous repair on the wiring harness at the Transmission Control Module (TCM) connector. The diagnostic technician repaired the bad connections. It was also noted that the ECM's internal terminating resistor was showing incorrect resistance, and an ECM replacement would be the next step if symptoms returned.
• YouTube diagnostic guide (General Motors Trucks (Silverado/Sierra)) — U0073 code, no-start, or limp mode immediately after receiving a jump-start.
  ❌ Tried (didn't work) Assuming the fault is a complex module or wiring issue without checking primary power.
  ✅ What actually fixed it A blown 175-Amp Mega Fuse located on the battery distribution block. A voltage spike or reversed polarity during the jump-start caused the fuse to blow as a protective measure. The fix was to test the fuse for continuity, replace the blown fuse, and perform a global power reset to clear any module logic locks.
• Multiple owner forums and YouTube videos (2014-2018 Chevrolet Silverado / GMC Sierra) — Flickering lights, radio shutting off, Stabilitrak/Park Assist warnings, intermittent stalling especially when turning at low speeds.
  ❌ Tried (didn't work) Replacing the battery., Replacing the alternator.
  ✅ What actually fixed it The issue was a poor ground connection at G218, located behind the driver's side kick panel. Factory foam insulation was caught under the ground lug, preventing a solid connection. The fix was to remove the 10mm nut, trim away the foam, clean the contact surfaces to bare metal, and securely retighten the ground lug.

"I Checked Everything" — The Actual Cause

• A smoke test on the EVAP system would be irrelevant for this code. The equivalent for a network code would be 'all wiring visually checks out'. In many U0073 cases, the wiring does look fine, but the actual cause is a high-resistance ground hidden under foam (G218), an internal (and invisible) failure of a terminating resistor inside a module like the ECM, or a blown Mega Fuse that isn't part of the standard diagnostic flow for communication codes.

OEM Part Supersession History

• 13533490 → N/A — This part number appears to be current for many GM applications, but part numbers are frequently superseded.
  Heads up: Always verify the correct part number for your specific vehicle's VIN with a GM dealer. Using an incorrect or non-programmed gateway module will result in a no-start condition or continued network faults.

Model Year Variations Within This Range

• 2015-2017: While there were minor mid-cycle enhancements (e.g., updated infotainment, new paint colors) to the K2XX platform, the core electrical architecture, including the use of a Serial Data Gateway Module and the location of critical grounds like G218, remained consistent. The diagnostic procedures and common causes for U0073 are largely identical across these model years.